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1. Original Message From Jeff King To css kenwood co jp kcc amateur kenwoodusa com sabura tech kenwood com au Cc k4oah mindspring com traian deck ro Bill Bailey Ken McVie Sent Saturday March 12 20056 41 AM Subject Question about TS 940 R149 and R 150 Appear to be in wrong places Dear Kenwood Customers Services I have found that when emailing Kenwood USA about a Kenwood USA product I got redirected to contact a Kenwood representative close to my home location I am not sure who is best to send this to So I am sending it onto to all Kenwood contacts Thank you for your recent replies While trying to find a fault in my TS 940 I have been going over the IF board It appears to me when the board was made it was marked with the screen printing lettering of R149 being where R150 should be and vice versa I have followed the board traces both in the Service Manual and on the back of a board and these resistors both seem to be in the wrong place This means Specified in First Service Manual Page 53 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm R149 68K R150 2 2M Specified in Revised Service Manual R149 150K R150K 2 2M Resistors as actually installed on my board if you follow the logic of the circuit diagram R149 2 2M R150 150K I have two IF boards here and they both have the resistors installed as required by the screen printing and hence on both boards both resis
2. I look forward to your reply Yours sincerely Page 97 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Jeff King PLL BOARD PROBLEMS PLL BOARD 0 Reseat Connectors Kenwood 940S Question Solved RMead100 aol com mailto RMead100 aol com Fri 7 Jun 2002 12 24 47 EDT At the suggestion of one of the list members I lugged the xcvr off its self and removed the cases and reseated all of the connectors on the boards which I had moved PLL and one underneath Also I reseated the connectors on theDigital A board above the PLL The missing bands are now working fine I think the connectors on the Digital A board are vulnerable to improper seating and being properly pulled loose ESPECIALLY when that board is lifted and tilted aside to get to the PLL board There is one very long connector on the front left of that board which seem to work itself loose at one side and needs to be looked at Thanks to all Randy K8BUX PLL BOARD 1 Remove the Black Foam from Behind the Board From kt4xw lt kt4xw gt Date Sun Jul 25 2004 9 41 am Subject Re TS 940 Very low output update kt4xw Hello This morning I had a chance to look at the rig again and found out some things that were interesting The power adjust control on the front panel along with the carrier control in cw all seem to work The output power goes up and down with adjustment With the power out adjustment VR2 all the way up the
3. Bill K4JYS Bill The problem is that the motor is drawing too much current at start up The supply voltage is applied through a series resistor and the excess current drawn because of the gummed up bearings is high enough to drop the supply voltage too low to start The correct fix is to replace the motor East Coast Parts has them but they are expensive 30 You might be able to find a hobby motor that will fit if you look long enough A temporary fix is to put an 18V Zener diode across the motor dropping resistor so that if the voltage Page 111 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm drop across the resistor is more than 18V the Zener conducts supplying enough voltage to start the motor Once the motor starts the voltage across the resistor drops below 18V and the Zener is out of the circuit BUT this is only a temporary fix If the motor freezes up the 940 WILL overheat significantly 73 Garey K4OAH Chicago Original Message From kenwood bounces mailman qth net mailto kenwood bounces mailman qth net On Behalf Of Garey Barrell Sent Monday 31 October 2005 4 10 a m To Bill Stewart Cc Kenwood mailman qth net Subject Re Kenwood TS 940S Cooling Fan Problem Walt I have been through this several times The problem is gummy or worn bearings in the fan motor The locked rotor current is too high dropping the supply voltage supplied through an 18k 1W resistor too
4. Just a quick question Which CW filter would you recommend YK 88C 1 or YG 455C 1 The price is very similar but I m not sure about Performances on 40mtrs band where the noise is stronger than for example on 15mtrs band Thanks 73 s Stjepan VK3TSN From ts 940 yahoogroups com mailto ts 940 yahoogroups com On Behalf Of John Rotondi Sent Friday 17 March 2006 10 07 p m To ts 940 yahoogroups com Subject ts 940 Re YK 88C 1 or YG 455C 1 Hello Stjepan First please note that the performance of these filters will not be evidenced by different performance on different bands since these are I F Intermediate Frequency Crystal Filters I F Stages are used to provide fixed selectivity across wide frequency ranges while rejecting image frequencies These are selectivity filters not noise filters they will not lessen noise within their passband but by having a reduced passband over the SSB 2 4KHz passband let s say they will pass less noise then the wider passband so the signal to noise ratio within the passband will be greater Please read the ARRL Handbook sections on Receivers for more information about I F stages The TS 940 has 4 Intermediate Frequency stages with the capability of inserting filters into both the 8 83MHz and the 455Khz I F Both the filters you ask about provide the same 500Hz bandpass characteristic and should provide similar results when compared against each other The YK 88C 1 is used in the 8 83MHz I F and
5. PERFORMANCE COMPARISONS MODIFICATIONS POWER SUPPLY IMPROVEMENTS ALC DELAY TIME TS 940 AVERAGE OUTPUT POWER SSB USE OF TS940S FSK RECEIVE FOR HF PACKET INQUIRY REGARDING USE OF ADDITIONAL RECVR GEIL CHIP FEEDBACK FROM READERS Page 3 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm PROMOTIONAL BROCHURE Page 4 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 5 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 6 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 7 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 8 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 9 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 10 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 11 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 12 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 13 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 14 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 h
6. When you swap R149 and R150 around you are putting the 2 2 Meg ohm in series with C 126 This effectively removes the Base line time constant to all AGC positions on the switch including AM even thou the switch does not function there That is why people say the meter is more jumpy Plus the 150K or 68K bias the gate of Q23 more heavy and allows the receiver to stay more sensitive to low level signals 73 John KI4NR LPC Wireless lpcwireless cfl rr com Phone 386 774 9921 Mr T Soranaka I look forward to receiving your advice Yours sincerely Jeff King 9 Original Message From Customer Service Section mailto css kenwood co jp Sent Tuesday 2 August 2005 6 01 p m To jaking es co nz Subject Re RE RE Is your advice Correct about TS 940 R149 and R 150 being in wrong places Dear Mr King Please accept my apologies for having supplied incorrect information A very experienced Kenwood repair expert from the USA is right The service manual is wrong on the schematic Yours sincerely T Soranaka Customer Support Center Page 47 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Kenwood Corporation Japan URL http www kenwood com Email css kenwood co jp 10 From John Brush mailto brushj comcast net Sent Monday 12 September 2005 2 29 p m To
7. gt Subject RE ts 940 Re Why don t more people use this group gt Date Mon 25 Apr 2005 09 09 42 1200 gt gt Thomas gt gt I found your review of the FETS most interesting gt My reason for writing is to ask you to tell me more about the pin diode modifications you have undertaken gt Where are these diodes and what do you do to replace them gt What else did you do to realign receive gt How did you establish the 0 15 uV sensitivity gt gt Yours sincerely gt Jeff King ZL4AI Page 83 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm gt From Jeff King lt jaking es co nz gt gt Reply To lt jaking es co nz gt gt To lt jaking es co nz gt gt Subject RE ts 940 gt Date Fri 29 Apr 2005 17 05 30 1200 gt gt Hi Tom gt gt Thanks this information is very interesting gt I really appreciate your advice on aligning the 940 very helpful information gt gt I also read below about pin diodes being changed in the IF board RX TX circuits Have you tried changing any of those gt gt Is the Temic s Vishay former Telefunken BA479 G or S suffix a suitable diode Spec sheet attached gt gt Yours sincerely gt Jeff King ZL4AI gt gt Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Monday 2 May 2005 9 23 a m To jaking es co nz
8. 1 I exchanged the PLL amplifier IC IC18 PLL board into a pair of extremely low noise OPamps which lowered phase noise However this required to tackle some problems with PLL instability 2 I have the optional 250 Hz CW filter for the 455 kHz IF When working PSK in SSB mode I missed the possibility to activate this filter I found out how to modify the 940 to allow for activation of the CW filter in SSB including the control LED at the narrow CW filter switch 3 When I bought my first 940 it came without the AT unit So I built one with an automatic antenna tuning board kit and built an interface which nicely communicated with the antenna tuning control circuit of the 940 Later I got the original AT 940 4 Follow hyperlink VOLTAGE_REGULATOR_HEAT_UP_AND_BFO_SHIFT 5 I equipped my 940s with the piexx boards which allows to control the 940 via the serial interface of a PC Best 73s for today Jeff Thomas DF5KF The following 2 emails have had some irrelevant content edited out gt From Jeff King lt jaking es co nz gt gt Reply To lt jaking es co nz gt gt To thomas hohlfeld lt thomas_hohlfeld hotmail com gt gt Subject RE ts 940 gt Date Fri 27 May 2005 19 35 16 1200 gt gt Hi Thomas gt gt Thanks for your email which I am still thinking about a lot gt gt Anyway I have been trying to get BA479G diodes from gt a supplie
9. 2 dB higher insertion loss than 1s2588 gt 10MHz Page 95 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Subject Re pin diode reversed FET Hello Jeff 0 35 dB is an INSIGNIFICANT amount of loss it is even dificult to detect a such low difference The positive aspect of the reduced IMD especially the second order IMD reduction is by far more important than the little loss My only doubt in such case is the parts and labour cost and if the mod is really needed for you there If you consider it as being needed if you have unwanted strong signals at your QTH and please consider the broadcast bands also then go for this mod with confidence Thomas is right the lower bands are really crowded here especially during the evening You are a lucky OM being there in ZL After 22 00 local time the 80m band is full here I can hear even the italian and DL stations making local QSO s with other I and DL stations there respectively and having some big signals as not to mention the russians which are everywhere and really strong like locals and S9 30 to 40 dB signals are usual The thousands of GU43 GU74 and GS35 power tubes are really put to work out there hi In my case the added city QRN is also high the normal noise is to 20 dB so I use the attenuator for to get the noise lower at a reasonable level as it have no sense seeing the S meter to S9 20 only because of the noise and so to loose
10. 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Makes a good 940 a great 940 I can now hear much better not I found the FET reversal change useless not worth the bother Have a Great Day 73 Bill KB9IV Minnesota 6 http www eham net articles 11090 7 Original Message From John mailto hydroaction cfl rr com Sent Friday 29 July 2005 4 03 a m To jaking es co nz Subject Your 940 observations Jeff I appreciate your efforts on the 940 I have to say the AGC deal is not quite right I have work on more 940 that I can remember I have known for years the silk screening of the numbers on the circuit board is wrong but the resistor placement on the board is correct also the service manual is wrong on the schematic The 2 2 Meg ohm resistor is in parallel with C 127 the 68K or 150K resistor is in series with C 126 which give you the base line time constant when AGC switch is in the fast postion This is the CORRECT arrangement Also if you look at the TS 930 that has the identical AGC circuit this is how it is on that radio too The reason why you get the AGC rise when the radio has been sitting is the Capacitors are leaky and by swapping the resistors around helps correct that problem I have had 940 s have the rising S meter problem and changing and the caps C128 C130 in the AGC fixed it This circuit is a Hi impedance type with FET very sensitive and crazy things happen I have check ma
11. 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Traian Belinas traian deck ro who diagnosed the problem and really understands these circuits Traian appears to have amazing skill and after reading the symptoms pointed me to look at R149 From there it became obvious the circuit was not assembled according to the circuit diagram Garey Barrell k4oah mindspring com Who provide some very useful advice on functions of components and explanations how to read the circuit diagrams A CAUTION Not all IF boards are identical I installed another IF board installed as per factory spec with R149 and R 150 in their other components position in my TS 940 It did not have the rising S meter problem But it was not sensitive to weak signals COMMUNICATIONS WITH KENWOOD JAPAN BELOW Original Message From Customer Service Section mailto css kenwood co jp Sent Tuesday 15 March 20057 11 p m To jaking es co nz Subject Re Question about TS 940 R149 and R 150 Appear to be in wrong places Dear Customer Thank you for your reply I suppose that currently R149 and R150 are mounted correctly as the screen printing lettering R149 and R150 are reversed Please confirm actual resistors comparing the circuit diagram The circuit diagram is correct Yours sincerely T Soranaka
12. IC19 pin 2 and IC17 pin 7 The one s that has have a low voltage on them are the PLL s out of lock Troubleshoot that PLL circuit Curt K8AI PLL Board 4 PLL Board and RF Board and PLL out of lock kc0bi lt kc0bi yahoo com gt wrote Hello everyone I am troubleshooting a TS 940S and it has at least two problems I tackled the easy one first it had a bad optical encoder and I replaced it with a known good pull from a TS 430S This unit definitely has PLL problems the exact frequency that it fails changes with heat but the general problem is this Above 10 MHz it works correctly in USB and LSB below 10 MHz it works only in USB There is an area between approximately 9 MHz and 10 MHz where it is probably unlocked but the frequency display still works and that point changes with heat Below 9 MHz it gives the all dots display indicating PLL unlock but seems to still work in USB I am using the built in 100 kHz calibrator as a signal After a period of time the nice sounding sine wave becomes a very ratty sounding tone This is true regardless of which sideband and at any frequency I ve tried Does anyone have an idea of where to start looking One of the PLL s must be losing lock Thanks in advance and 73 Harold W0HJW formerly KC0BI From mailto TS930S yahoogroups com On Behalf Of Bill K0ZL Sent Wednesday 19 October 2005 11 47 p m To TS930S yahoogroups com Subject Re TS930S TS 940S Phase Lock Loop Problems Drop your
13. TS 940S Revised Service Manual 62 pages SO1 service adjustment instructions SP 940 Service Manual VS1 Voice Synthesiser Unit Service Manual Page 116 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm TS 940S operators manual 108 pages TS 940S Technical Supplement 48 pages TS 940S promotional brochure 9in full colour IF10B Instruction Manual internal kit for computer interface control IF232 Instruction Manual external control unit for computer interface control PC1A Phone Patch Operator Manual and wiring Diagram YK 88CN manual SWR 2000 Service Manual HS5 Operators manual headphones SM220 Service Manual 29 pages Station Monitor TL 922 Service Manual 1 500 watt linear amplifier TS570 Control Program fully operational MC 43 operators manual MC 60 operators manual MC 85 operators manual MC 90 operators manual Kenwood miscellaneous connectors schedule All files on this website If you require the CD cost is US11 00 plus postage Please jaking es co nz to request delivery Identifying When Radio Manufactured ZL4AI advice Manufactured from approx mid 1985 to 1990 ZL4AI does not know the exact dates and would appreciate being emailed this information 940s was reviewed by QST in Feb 1986 so production began before then The 950s came out and was reviewed by QST in Jan 1991 Production of the 940 probably stopped in late 1990 A well talked ab
14. This fan has sealed permanently lubricated bearings if it is like the one on my TS 940 With this type of motor I have had some results in lubricating motors like this by taking a straight pin and pricking a small hole in the cover over the bearings and injecting a light oil through the hole This will possibly extend the life for a short period but in my experience it is time for a new set of bearings or in this case a new fan motor Bill AL7BB by WG7X on February 21 2001 My TS 940S and two of those owned by fellow hams have developed the noisy fan Like another poster I oiled my motor and that helped for a little while Eventually the motor failed and had to be replaced You should also be aware that there are two of these fans Number one and usually the one that fails is the one on the back of the transformer Number two is the fan on the finals This fan can be seen inside the rig Look down through the slots on the top cabinet in the right hand side in front of the finals This fan probably would be a bear to change Thankfully the ohter fan seems to fail more often These fans go for about 32 US I bought two just in case Sometimes I also use an auxillary fan over the transformer Of course this intorduces a little extra fan noise into the shack I might eventually replace the back fan with a full time muffin fan on the back transformer I tried that while waiting for the replacement fans to arrive A six inch fan does a great job
15. What is new in Version 15 SUMMARY OF R149 AND R150 MIS LABELLING What is new in Version 14 BATTERIES INTERNAL BATTERY REPLACEMENT CW FILTERS Motor bearings gummed up Page 1 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Field measurements of receiver improvement following FET swap What is new in Version 13 PROMOTIONAL BROCHURE SERVICE MANUAL amp SERIAL NUMBERS What is new in Version 12 PLL BOARD 4 PLL BOARD AND RF BOARD AND PLL OUT OF LOCK AVR BOARD amp POWER SUPPLY FAN AND TEMPERATURES COOL AVR COMPONENTS BY REMOUNTING ON HEAT SINK POWER SUPPLY HEAT SINK RUNS TOO HOT VERIFY THERMISTOR 101 IS ATTACHED AND FUNCTIONING INDEX PROMOTIONAL BROCHURE RECEIVER PERFORMANCE IMPROVEMENTS R1 KENWOOD PRODUCED 3 SERVICES BULLETINS WHICH DO CONSIDERABLY IMPROVE THE RECEIVER RECEIVER 2 FIELD EFFECT TRANSISTORS AROUND THE WRONG WAY RECEIVER 3 THERE IS NO AGC TIMING CORRECTION SUMMARY OF R149 AND R150 MIS LABELLING Mike KC8ZNW on 25 4 05 describes this same behaviour to the Kenwood net Executive Summary of AGC Mod Independent Feedback on how Receiver Improves THE PRODUCTION MISTAKE DESCRIBED TO CHANGE THE RESISTORS THE INITIAL PROBLEM SYMPTOMS ACKNOWLEDGEMENTS TO PERSONS WHO HELPED SOLVE THIS A CAUTION COMMUNICATIONS WITH KENWOOD JAPAN BELOW RECEIVER 4 PIN DIODE IMPROVEMENTS 4 1 Background on how Pin Diodes were discovered to improve radios 4 2 RadCom
16. of cooling the power supply In fact it does a BETTER job of cooling the rig I know this because I used a Fluke DVM with a temp probe to measure the temp of the cooling fins With the stock fan the thermistor kicks in at about 45 deg C With the muffin fan I was able to keep the temp at about 20 deg C Gary WG7X Page 104 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm by AL7B on March 22 2001 I replaced my fan about 8 years ago with one used for cooling a 486 computer chip I was too cheap to pay Kenwood 35 for a new motor After tweaking the brushes a few times I gave up I did have to pack foam around the opening to force the air through the fan but it has worked fine over the years Something to think about anyway and hope this helps Dick Anchorage AK COOL AVR COMPONENTS BY REMOUNTING ON HEAT SINK From Victor Zelenin lt vic_kz mail ru gt To jaking es co nz Date Tue 27 Sep 2005 17 09 12 0400 Subject TS940 Mods Dear Jeff Thank You for the nice page about Kenwood TS940S I have a small question to Thomas DK5KF and to Jeff as experts I am waiting replay from both of you DK5KF wrote the mod N4 Voltage regulator heats up and causes a shift in BFO on IF Board In my TS940 there is the shift in BFO due the warm up The shift is about 150 Hz per first 30 min of operation Thomas advice to be careful with the IC7 voltage regulator on the Control Unit From my assumption it is god to
17. operating at temperature degrees C Rated operating temperature degrees C D1 D2 D4SC6M 60V 4A 76 40 to 150 D10 D11 D12 and D13 1N5408 1000V 3A 76 65 to 150 C12 45 on top 85 Page 106 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm design which allows these components to run so hot So what do D10 to D13 do It is hard to tell with above AVR circuit diagram so lest redraw the circuit below Page 107 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm AC 3 C12 D10 AC 4 D13 D11 D12 This diagram is still under construction Intention when finished is to show bridge rectifier can be put in here Page 108 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm ZL4AI undertook more measurements and a modification ZL4AI followed through circuits feed by line 21T All other lines appear except the DC DC unit appear to end in voltage regulators or similar semiconductors which put out even lower voltage at a level controlled by the semiconductor rather than the initial 21v feed value The exception is the DC_DC unit which feeds through a transformer to supply the high voltage feed of 44 4v display The 44 4 v is the only voltage that is directly reduced by lowering the voltage on 21T It does not appear wise to lower the display voltage If an
18. recording and TV Film post production facilities for many years When I first did the FET fix to my TS 940 the results were obvious to my ears In doing the second radio with my friend we systematically followed these steps to document the results relative to an external repeatable test signal independent of band conditions QSB etc 1 Set up the signal source my MFJ 259 antenna analyzer with whip antenna to generate a signal near 14 200 MHz 2 Set up the TS 940 with a small whip antenna on the work table about 4 feet from the test source Note that the MFJ 259 RF test signal is fixed in level so this would not be a variable in these tests 3 Tuned the TS 940 to this test signal peaking the carrier reception in USB mode and recording the maximum S meter reading Note that I moved the radio around a bit to ensure that the reading was stable and repeatable and not sensitive to relative position 4 Shut off the test source so as not to deplete the battery while working on the radio 5 Reversed the first of the FETs reinstalled it s PC board installed the whip antenna and positioned the radio as for the original measurement 6 Powered up the test source and tuned the TS 940 to it as before There was a full 1 S unit increase in received signal level 7 Shut off the test source 8 Reversed the second of the FETs reinstalled it s PC board installed the whip antenna and positioned the radio as for the original measurement Page 37 o
19. 5 mil TS 940 with a later model 8 Mil IF board in it much much better Also Kenwood put an S meter slam mod in those boards all the older 940 when you shut the radio off pin the S meter over The newer boards are fix for that 8 From Jeff King mailto jaking es co nz Sent Monday 1 August 2005 8 01 a m To css kenwood co jp Cc lpcwireless cfl rr com Subject RE RE Is your advice Correct about TS 940 R149 and R 150 being in wrong places Dear Mr T Soranaka Thank you so much for your 2 emails sent in March 2005 attached as below COMMUNICATIONS_WITH_KENWOOD_JAPAN About R149 amp R150 From your advice I understood The I F circuit diagram is correct about positions of R150 and R 149 and the I F board is labelled incorrectly Because your advice was valuable I recorded this to a small web page http homepages ihug co nz jaking TS 940_02 htm This has been seen by some TS 940 enthusiasts It enables one to adjust a TS 940 to operate as you advised Kenwood designers really intended A very experienced Kenwood repair expert from the USA very strongly suggests your advice may not be correct The reasons he states sound correct and are very convincing Those reasons are summarised below With the greatest of respect to Kenwood Corporation and yourself I ask please Could you please review your advice and advise again if R150 and R149 on the IF Board should be swapped around to make the TS 940 to operate as Kenwood design
20. 6 Over the past five years usin in some serious DX contest I have yet failed to see where these expensive HP PIN diodes made any substantial im TenTec runs about 10ma of current through their production PIN diodes in order to gain the full IM advantage of t through the HP PIN diodes So the bottom line is if you replace the PIN or silicon diodes in a rig you will see hear practically no improvemen utilize the diodes operating at their optimum design specifications Probably if you find the filter switching diodes probably means that someone has taken the time to change the current running through the switching diodes to real At 01 32 PM 9 17 97 0400 you wrote gt H M Puck Motley W4PM wrote gt gt I have the feeling that the pin diodes in question are a modification gt gt suggested in an article by Ulrich Rhode not sure of the spelling of his gt gt name a few years back concerning 2nd order IMD in modern rigs One of gt gt the rigs mentioned was the Paragon The article stated that by replacing gt gt the common switching diodes used to switch the receiver front end band gt gt pass filters with a certain type of pin diode 2nd order IMD could be gt gt improved Maybe some of our more technically oriented folks remember this gt gt article and can comment in greater detail This is all I remember so if gt gt you have additional questions don t ask me gt Thanks Puck I was certain it was something Rohde said just was
21. F circuit diagram was correct and the I F board was labelled incorrectly Communications_1_2_with_Kenwood_Japan Kenwood Japan have now changed their mind and confirmed The I F circuit diagram is incorrect Communication 3 with Kenwood Japan Swapping R149 and R150 probably increases sensitivity to similar degree as achieved by just turning the AGC off Please review KI4NR s email below advising the Kenwood intended correct construction was electrical Page 39 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm layout of the AGC identical to the TS 930 KINR_email KI4NR advises the rising S meter caused is leaking in C128 and C130 On the Editors radio C128 has been replaced and does not fix the rising S meter When time permits C130 and or other AGC capacitors will be replaced and when replacement has been shown to remove the rising S meter this web page will be updated to confirm that At that time this section of the web page will be restructured to separate communications about IF circuit diagram from the rising S meter problem SUMMARY OF R149 AND R150 MIS LABELLING Kenwood appears to have done the following Please note there are 2 mistakes 1 First incorrectly labelled the schematic with resistor values around the wrong way 2 Then incorrectly labelled the PC board to correct the mistakes on the schematic so correct resister values put in circuit For example the position of R150 was
22. KC8ZNW Executive Summary of AGC Mod Its easy to modify a TS 940S to hear better or as well as a TS 950SDX When fixed TS 940 really pulls out those very weak signals Simply swapping 2 resistors around will enable this rig to hear as Kenwood designed and intended in Kenwood s original circuit diagram The error is on the IF board Kenwood printed labels for R149 and R150 around the wrong way As assembled by the factory the outcome is in the main signal path a 2 200 Kilo Ohm resistor ends up where a 150 Kilo Ohm Resistor should be Being 14 times larger the 2 200 Kilo Ohm resistor incorrectly significantly degrades the signal Swap the resistors around and the receiver hearing improves significantly Kenwood have confirmed the resistors are in the wrong place Their emails are below Probably these resistors in the wrong place occurs in every TS 940S produced Independent Feedback on how Receiver Improves 1 From Ed mailto ca urso2 verizon net Sent Monday 23 May 2005 7 18 a m To jaking es co nz Subject TS 940S Also your AGC Timing Correction was applied on my rig SN 806XXXX and worked great Sure enough resistors R149 68K on my equip and R150 2 2Meg had been incorrectly installed by the Mfr The board markings for those resistors were wrong 73 Ed Alves KD6EU USA Full email at FeedbacK_3 Page 42 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 2 From el34
23. Kenwood Diode Original Spec Operating Frequency MHz Replacement Replacement Spec D3 1s2588 L30 DIODE TW 4000A 3 15 0 5 Don t replace until testing verifies suitability D4 1s2588 0 5 Don t replace BA479 0 3 dB loss is too great D5 1s2588 0 5 1 5 Don t replace until testing verifies suitability D6 1s2588 0 5 1 5 Don t replace BA479 0 3 dB loss is too great D8 1s2588 1 5 gt 3 0 Don t replace BA479 0 3 dB loss is too great D10 1s2588 3 4 Don t replace BA479 0 35 dB loss is too great D12 1s2588 4 7 Don t replace BA479 0 3 dB loss is too great D14 1s2588 7 8 5 Don t replace BA479 0 3 dB loss is too great D7 1s2588 1 5 gt 3 0 PIN type BA479 SI D 30V 50mA 100MHz D9 1s2588 3 4 PIN type BA479 SI D 30V 50mA 100MHz Page 94 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Whether you install many pin diodes depends on how crowded the bands are at your location More information below explains this Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Tuesday 21 June 2005 9 16 a m To jaking es co nz Subject RE Hi Jeff yes I think that 0 3 0 4 dB is almost nothing Remember that one S unit makes 6 dB 20 fold more The additional loss caused by the pin diodes therefore is a very small fraction of an S unit A few meters of RG58 antenna cable with convent
24. RF unit down rig up on it s left side and resolder all around the VCO area which is about the front 2 3 of the board Also resolder around the RF RX preamp and first mixer area that is on the same unit the narrower shielded area about mid way back Be patient you have about a two hour job there Use bright light and drugstore reading glasses to make sure you get them all and watch for bridges as you solder Much easier to find and clean them as you go rather than discover them later Next get the PLL unit out scrape the adhesive pad from under the VCO nearest the front right cornner of the board as the rig is facing you and Resolder that area about 1 sq inch Page 100 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Next do the PLL VCO service note Editors Comment this is Service Bulletin 900 which should be in the files section of the group Requires an RF probe for your DVM 73 Bill K0ZL CONTROL BOARD VOLTAGE REGULATOR HEATS UP AND CAUSES A SHIFT IN BFO ON IF BOARD Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Monday 2 May 2005 9 23 a m To jaking es co nz Subject RE ts 940 4 One of the voltage regulators on the control board warms up the bottom of the 940 which causes a small but detectable shift of the BFO on the IF board I removed this regulator from the control board and mounted it on the big aluminium heat sink at the rea
25. So in some instances putting in replacement Pin Diodes in the receive path up to the first mixer can increase the receive signal It is good practice to bench test and verify whether a replacement Pin Diode does pass more signal than the existing diode Note The BA479 diodes described below according to their spec sheet have Wide frequency range 10 MHz to 1 GHz Possibly this means BA479 do not pass signal below 10 m Hz BREAKING NEWS DF5KF has just discovered the BA479G attenuates less signal than the original TS 940 diode only at frequencies lower than 10 MHz DF5KF is still testing and more information is to come See below 4 4 Experience from Persons who modified the TS 940 First from www contesting com TopBand WSVHF TS 940 Specs km1h juno com mailto km1h juno com Thu 05 Mar 1998 10 30 41 EST To all those on Topband who asked here is the results of the TS 940 tests 73 Carl KM1H Begin forwarded message From km1h juno com km1h juno com To wsvhf qth net Subject WSVHF TS 940 Specs Date Tue 09 Sep 1997 22 35 15 EDT Message ID lt 19970909 214104 9687 15 km1h juno com gt As an addition to the Sherwood receiver info here are some specs on a TS 940 All tests were run on 28MHz during the past few days on a customers unit Page 81 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm TS 940 late serial with factory phase noise updates MD
26. be that way there are engineering solutions that could easily deliver the full IARU specification but when everybody on HF is five nine anyway who cares any more Measurement Adjustment Item Condition Test equipment Unit Terminal Unit Part Method 6 1 S meter BAND 14 175MHz SSG output 14 175 MHz 0dB u SSG AF V M SP SCOPE IF VR3 Adjust meter nee for mechanical f RF VR1 Set the VR1 to CCW 6 2 S meter SSG output 8dB u AGC FAST IF VR1 ADJ to S1 6 3 SSG output 40dB u IF VR4 ADJ to S9 6 4 SSG output 100dB u Verify full scale 6 5 Repeat ADJ S1 a S9 Page 129 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm gt gt 73 from Ian G3SEK Ian and all As has been said before the manufacturers correctly assume that the majority of buyers are technical idiots Have a S meter that has 1 dB per S unit and about 5 uV for S 9 is a good marketing thing Besides it s a lot cheaper to build I would hope that anyone who actually cares about such things would take the time to calibrate the meter on their store bought radio Since I do this with all my radios I would not care to pay extra for a manufacture to make a feeble attempt at a real meter Using a HP8648C generator at 14 1 MHz this last time I produced the following chart for my FT1000D S1 103 5 dBm S2 101 5 dBm S3 98 dBm S4 94 dBm S5 90 dBm S6 85 dBm S7 80 dB
27. better at pulling weaker signals up out of the crud Even with noise blanker on the 940 lost some of its ears Noise blankers on both rigs eliminated the noise HEARD but the 1000MP was better at finding signals and bringing them up than the 940 with DSP59 was 4 15 Bill Tippett reports that his 1000MP is extremely clean no intermod products observed compared to the TS930 he retired COMPARISON WITH OMNI VI I wanted to test an Omni VI but none to be borrowed locally so I asked NE3H for his opinion see above In the meantime power company has repaired a number of defective lightning arresters a bad transformer and God knows what else to the point where my line noise is now S3 or less most of the time so the 940 gets a reprieve I fact even though it s almost too late in the season am working DX on 160 most evenings now when I could not hear it in winter With a little luck I might hit 50 countries for the 96 97 season I wish I could find the mail messages I sent to George because there was more specific info in them but this report is the bottom line From my own observation the 1000MP and the TS570 outperform the TS940 receiver with high line noise levels Mechanical filters are needed on both rigs But with little line noise the 940 is still pretty dang good Thanks to K9IG formerly KO9Y and N9QCT for the loan of their rigs Mel KJ9C Page 142 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_0
28. can accept both of these consequences You can install the lamp clip leading a resistor in series with it then looking at the meter or display under normal room lighting to see if it s okay for you own particular situation To arrive at the right resistor values simply use Ohm s Law plugging in the correct numbers for your own transceiver s lamp supply Voltage drop desired divided by the lamp s rated current equals the resistance needed and Voltage drop desired times the lamp s rated current equals the resistor s wattage By way of an example let s take the Radio Shack 272 1092 lamp that I mentioned before which has a current rating of 60 mA or 06 Amp Let s say we d like to drop the 12 volts feeding the lamp down to 10 volts or a 2 volt total drop We plug in the numbers 2 volts divided by 06 amp equals 33 ohms and 2 volts times 06 amp equals 12 watt Now we know that we ll need a 33 ohm 1 4 to 1 2 watt resistor in series with each lamp in order to drop the 12 volt lamp supply down to 10 volts A 1 2 watt resistor will provide a 4 times safety margin for heat dissipation dissipation ratings for resistors generally assume their full lead length in free air so it s Page 121 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm safest to over rate them by 2 to 4 times for shorter lead lengths and operation within confined enclosures By the way try to avoid using bulbs intended for flash
29. coax connection The fan might be a little noisy that s ok cuz it never runs at full 12v bill ZL4AI changed R11 to 470 ohms Afterwards with temperature probe in the hole in the heat sink beside thermistor 101 and the case off the fans starts at 48 50 degrees C and stops at 27 degrees C Case on above the heat sink beside thermistor 101 fan starts at 41 degrees C and stops at about 27 degrees C This is a very safe modification and highly recommended You might at worst wear our the fan motor at a cost of 30 replacement compared with gt 200 of transistors and many hors of repair time if Q101 or Q102 over heat VERIFY THERMISTOR 101 IS ATTACHED AND FUNCTIONING ZL4AI 940 had a very hot TS 940 power supply On removing the power supply heat sink the thermistor 101 actually fell out of its housing metal housing It had become unglued It had been sitting in the correct position but probably was not making adequate contact thermal heat transfer Hence not turning on the cooling fan To verify the thermistor changed resistance I connected a ohm meter and heated the thermistor with soldering iron It went from approx 16 700 ohms at 12 degrees C to 220 ohms at say 400 degrees C I have no idea if these are correct resistance values but they give an indication of what happened If anyone has the temperature table for Thermistor 101 please send to jaking es co nz Page 110 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS
30. digital reduction was better On the contrary the noise blanker on the 940 seems to be a little better than the 570 s However as you know strong signals tend to swamp receivers with noise blankers ON The 570 noise REDUCTION beat the DSP59 NR feature The 570 was tested without an IF filter installed and it did exhibit some overload from adjacent signals since then Eric has installed a 500 Hz IF filter and reports that adjacent signal swamping is negligible and he can crank the DSP down to 100 Hz without ringing The DSP is the selling point of this receiver better signal to noise than the 940 with STRONG noise and therefore can dig out the weaker ones However in the absence of strong line noise say S3 or lower the TS940 with outboard DSP seems to work pretty well See below The CW autotune works with relatively weak signals but not down in the mud This makes tuning with tight bandpass a lot easier Page 141 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Very little SSB testing but the heterodyne filter works as good or better than the one on the 59 DSP Did not have multiple heterodynes to see how it works but would guess OK Forgot to check for transverter input Dope Suppose that auxiliary receive antenna is possible somehow COMPARISON OF TS940 TO YAESU 1000MP I borrowed K9IG s 1000MP for similar testing I felt like I should sign away rights to my firstborn grandchild
31. here in Maryland picked up a 570 about 2 months ago and after a week said it was pretty good but he HAD to get the optional filter to make it decent on low band CW for receive Have you had other comments The few guys I know with OMNI V and VI praise them highly for low phase noise and tremendous RX capabilities I am using a TS830S It replaced a Drake 4 line Tough to keep up with technology and I refuse to pay for a 100 memory tranceiver when I don t need all those bells and whistles 73 Sid K8GG asks about the 570 comments on TS950 Have you read the review by Doug DeMaw W1FB in the March 1997 issue of CQ Magazine It reads well but raises the questions I have written here below 1 I wonder if the only way to get a beverage hooked up is to change antenna selections on the front panel 2 I also wonder if there are plug in slots for more than one extra filter I don t need a 1 8 Khz SSB filter with slope tuning but I would like to have both the 500 and 270 Hz filters in the 8 8 MHz IF That is one complaint about the TS950SDX There is room for both the 500 and 250 Hz IF filters in the 455 Khz IF but only one CW filter in the 8 8 IF and it is more important to have selectivity in the first possible stage 2nd IF rather than in the next stage 3rd IF Obviously it does not have the DSP available in the TS570 I may send Doug an SASE and note and see what happens He now
32. labelled as R149 on the PC Board which resulted in a 150K resistor being put at the R150 position Page 40 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Areas in grey below should be disregarded Significantly improves the AGC timing function After modification You hear weak signals a lot better S meter with AGC SLOW ON becomes quite responsive and lively in the region of S1 to S4 signals Before S meter did not move much in S1 to S4 region Before it would take a strong signal to lift the meter suddenly to S4 I always wondered why the TS 940 behaved differently to other transceivers TS 930S TS950SDX which react much faster over S1 to S4 Mike KC8ZNW on 25 4 05 describes this same behaviour to the Kenwood net Hello everyone I have a question about the movement of my 940 s meter It seems Page 41 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm that it barely moves on some signals which are perfectly readable other sigs give me 8 or 9 and I have even heard an occasional 10DB movement My TS830S will give me a 2 or 3 s unit increase when I switch the antenna to it for the same signal Is this an effect of the sensitivity of the receive section Or do I have a malfunction In addition my VFO exhibits the occasional hiccup on the last 2 digits on small movements of the knob I understand this may be caused by solder joints TIA Mike
33. lives maybe 175 miles NNW of me 73 GL George K8GG Another comment from K8GG George Guerin As I saw the TS 870 show at the W9DXCC a couple of years ago there are NO IF filters That model uses digital filtering at about 17 Khz to shape the passband Problem is the images 34 khz away There is no plan to put in filters although a couple of California hams have done it WONDER Page 140 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm WHO With out a 2 7 Khz filter at the 8 8 or 455 IF it has troubles from what I know Kenwood is NOT planning to make filters optional I do understand using the SSB filter and digitally making the CW filter in the 4th IF works fine On the TS 570 Is there an accessory socket like the TS 940 and TS 930 that has the ability to pull out and put back in the RX antenna line SEE ANSWER BELOW That is my fear The Icom radios like the 740 751A 765 and 775 all have a coax jumper for the RX antenna line The 728 and 726 do not I complained to the Icom rep s at Dayton The TS 950SDX has a jumper like most of the Icom radios There is a guy in Ft Wayne who makes FEP s front end protectors If you can figure a way to bring out the RX antenna line it is a neat way to make sure the RX input is grounded on transmit It is written up but not in enough detail in one of the recent CQ Mag s as well
34. low to start the motor The fan will start sometimes if you spin the blade to get it started The fan will start and run fine if the supply is stiff enough All Bill has to do is measure the voltage across the 18k resistor and he will see about 22V The transistor will be saturated and about a volt across the motor winding An 18V Zener across the resistor will allow the motor to start and once it starts the voltage across the resistor will drop to about 12V and about 9 10V across the motor But once the motor stops altogether which it will the transceiver WILL overheat damaging AVR board parts first and if you re unlucky the PS pass transistor will short putting 40V across the final and driver transistors The fan motor will sound cheap then 73 Garey K4OAH Chicago RF BOARD 1 Board Runs very Hot Page 112 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Kenwood ts940s PCB burning Clif mailto clif avvid com Tue 4 Mar 2003 20 06 53 0600 That is the way they run very hot Reflow the solder on them with good solder and don t worry about it Clif Holland KA5IPF AVVid Authorized Kenwood and Icom Service www avvid com Original Message From PY2NFE lt py2nfe uol com br gt To Kenwood lt kenwood mailman qth net gt Sent Tuesday March 04 2003 7 52 PM Subject Kenwood ts940s PCB burning Hi Gang I need a help A TS940S is with a part from the printed plate of circu
35. may not worth doing it It is only a decision of each of us depending also on the local Rx conditions This is what I intended to let you know before The mod shall be more usefull for me here but I am not decided because I will have to sell all the radios some day so no reason for spending and effort for such mod and I consider also that some buyers don t like buying the modified radios Now I must admit I am not sure if I Need these pin diodes Now propagation is not good I am only really listening on 20 at about 3 UTC According to Thomas if one want to avoid losses I probably should only be interested in changing the diodes below 10 MHz so this is really only going to improve 40m and 80m Yes this is done on some Rx as the Icom R9000 where the Rx BPF are splitted in two banks LF MH and HF switched by good PINs the other diodes are normal The TS950 SDX Rx BPFs are also separated in two banks by a HPF filter which attenuate the LF MF signals when using the higher bands for avoiding the 2nd order IMD caused by the LF MF broadcast signals This is the only difference between the TS950SD and TS950SDX regarding the RF board front end and some amateurs that are not aware of this are still speaking of the big difference between the two radios Now I m convinced not to do the PIN diode mod I think you are right I do not need it here where there is little interference
36. than AGC fast 3 Original Message From Michael Feryok II mailto mikeferyok yahoo com Sent Saturday 9 July 2005 9 57 a m To jaking es co nz Subject AGC Mod Hey Jeff Thanks so much for your TS940 page it helped a co worker and I today to swap the R149 150 resistors for the AGC mod Very apparent improvement in noise level and gain I can hear stations that are buried into the noise floor now Mike KC8ZNW From ts 940 yahoogroups com mailto ts 940 yahoogroups com On Behalf Of mikeferyok Sent Saturday 9 July 2005 9 53 a m To ts 940 yahoogroups com Subject ts 940 AGC mod works great My friend and I did the R149 R150 swap and it improved the gain and noise level Adjusted the VR3 for a proper zero on the meter and Page 43 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm worked LZ1YE and YV5YMA right after on 17 meters Very low noise compared to before the swap I highly recommend it Thanks to everyone here and Jeff ZL4AI Mike KC8ZNW I m still debating the transistor gain swap 4 From ts 940 yahoogroups com mailto ts 940 yahoogroups com On Behalf Of Dale Sent Tuesday 12 July 2005 5 37 a m To ts 940 yahoogroups com Subject ts 940 Re AGC mod works great Hello Mike I m having both mods done to my 940 now and I hope the out come is like yours I ll post after I get my 940 back and let everyone know how it goes I have a very late model serial numb
37. used a solder vacuum and solder wick to carefully remove the old solder from each of the old pins that I know and even suspect are bad This process is repeated for any solder point that is suspect on the rest of the components on the board As you can imagine this process takes some time When I completed the control board it was re installed into the rig and the transistor heat sinks and disconnected plug bodies were re installed Page 122 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm After completing the process noted above I repeated the process for each of the other remaining boards on the rig There are 5 other main pcb boards on the rig not counting the little specialized boards located on the back of the main panel I went through each pcb with the same process finding and correcting more bad or suspect solder connections In summary total I corrected 2 completely disconnected plug bodies 12 14 visually obvious cold solder connections and another 30 or so suspected bad connections on various plugs and components BATTERIES INTERNAL There are two 1 Behind switch Unit L X412 1600 00 2 On Digital A Board X54 1830 00 Page 123 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Typical symptoms for the Switch Unit battery failing are From TS930S yahoogroups com mailto TS930S yahoogroups com On Behalf Of Jim Bazsika Sent Tuesday 21 Ma
38. very interested to read Hawker s article you mention Your mail also made me re think about this mod The G version of the BA479 has been suggested to be better for short wave purposes but it is true that there is not much evidence in the datasheet My guess is that the BA479 should simply be measured in a test setup and this is what I started yesterday I set up a simple circuit with two RF generators 300 mV out fed into a hybrid combiner the output of the combiner going into one end of the diode under test The other end of the diode was coupled via a step attenuator into a spectrum analyser my shack is a museum of old instruments hi I fed a forward current of about 10mA through the diode uncoupled from RF of course The generators were adjusted between 2 and 15 MHz always 500 kHz apart two tone signal I hadn t much time and did only some very short measurements Anyway the results were interesting Here they are 1 A conventional all purpose diode 1N4148 produced a horrible spectrum of intermodulation products In addition the insertion loss was high up to 10 dB 2 Next I inserted one of the original diodes which I replaced in my TS 940 of course I did not through them away The difference was impressing At 10 MHz and above these diodes produced very little intermodulation distortion with very low insertion loss 1 dB or so Below 10 MHz the intermodulation became worse and was poor at 3 5 and below Interestingly i
39. 0 RH1 285 24 5 24 7 20 4 5 45 9 45 4 4 CR 2450 NRH 540 24 5 24 7 17 8 7 35 11 35 5 9 CR 2450 NRH1 540 24 5 24 7 20 4 7 35 11 35 5 9 CR 2477 NRH 950 24 5 24 7 17 8 10 05 14 08 8 4 Page 125 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Cut one leg off the plug and solder it into the hole that was left when you unsoldered the old battery To get at the battery remove the top side screws on the front loosen bottom screws and tip the front face forward Then un plug take out screws and remove Switch Unit L Unsolder the battery wires and soldered in the new plugs Reassemble Find a small enclose to hold the battery so if it leaks the enclose contains the leaking fluid Attach this container by Velcro to a convenient point inside the radio This way next time I replace a battery it will be just a plug in without having to take the 940 apart so much Next time I will look at using AAA size 3V lithium in a battery holder With the potenetail long life from newer AAA lithium battery may never have to replace the again Yours sincerely Jeff King ZL4AI DU7 INFORMATION NOT ANNOUNCED by KENWOOD While working on IF Boards the following parts were found to be missing Any information as to why Kenwood removed these parts would be appreciated If box below empty means existence of component not yet searched for First Edition Service Manual Revised Edition Service Manual Serial n
40. 06 http homepages ihug co nz jaking TS 940_02 htm Page 71 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 72 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 73 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 74 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 75 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 76 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 77 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 78 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 79 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 80 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 4 3 Summary of Key points on Purpose of Pin Diodes by ZL4AI Diodes are inferior switches than relays Diodes are used as a cheaper alternative to keep the cost of amateur radios down Diode switches leak and cause adjacent transmit intermodulation signals on the air Pin Diodes leak less and reduce intermodulation signals Some Pin Diodes notably the BA482 attenuate less radio signal
41. 19 will probably be improved by changing into suitable pin diodes such as the BA479 Those who use the TS 940 only with a beam antenna e g 20 10m which is unlikely to deliver large signals at 80 and 160m will probably not have much benefit The two switching diodes between the bandpass filters and the preamplifier may also be replaced by pin diodes at the lower bands D6 D8 D14 and D21 I would not recommend to exchange D16 D18 and D20 because the original diodes are already excellent at the higher bands and the pin diodes would add nothing else than a minimal increase of insertion loss In addition to the front end diodes there are also numerous switching diodes in the IF unit Particularly those before the 8MHz crystal filters may be considered for replacement by pin diodes I can imagine that this will improve narrow band intermodulation I d be curious if anybody else has experience with this If not I may check out this point in future Your last mail says you ordered 40 BA479 diodes so it seems you found a source I for myself also ordered 50 BA479 from Schuricht here in Germany It s good to have some on stock for future projects and people say these parts are likely to be replaced by SMD types in future If you still need BA479 let me know and I will try to help By the way there are probably excellent alternatives The TS 940 uses in its front end an attenuation pad which is part of the AGC D23 and 26
42. 2 htm FAQ on WWW http www contesting com topband html Original Message From kenwood bounces mailman qth net mailto kenwood bounces mailman qth net On Behalf Of Mike McCarthy W1NR Sent Wednesday 13 July 2005 1 13 a m To Philip Neidlinger kenwood mailman qth net Subject Re Kenwood New TS 940S Original Message From Philip Neidlinger lt PNeidlinger dwginc com gt To lt kenwood mailman qth net gt Sent Tuesday July 12 2005 8 45 AM Subject Kenwood New TS 940S gt Yes I know the 850 is probably a better rig but I like to have an analogue meter on my radios No it s not The quad conversion of the 940 blows the doors off the 850 I ve used them side by side Mike W1NR MODIFICATIONS POWER SUPPLY IMPROVEMENTS Original Message From John mailto hydroaction cfl rr com Sent Sunday 10 April 2005 3 06 a m To jaking es co nz Subject Re Advice on what to do upgrade TS 940 PowerSupply First thing Replace all the Zener diodes on the AVR board with 1 watt Units Same voltage values you will have to open the hole up slightly to allow for larger leads on new parts D 3 D 4 D 8 D 9 D 14 Page 143 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm D 1 2 10 13 are all ok just leave them They are 2 5amp at 100Vpiv Q 1 and Q 2 Q 6 are fine Just replace them with same replace C 3 C 4 C 6 with 2200UF 50volts replace C 13 too Pu
43. 2006 http homepages ihug co nz jaking TS 940_02 htm Page 33 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm After reading Kenwood s Garey s and Traian s advice I turned around only Q4 on the IF board The result was a quieter receiver I do not believe that there was any significant gain increase in the receiver I would appreciate and will post on this page emails describing others experience regarding this change From Kenwood net on 25 4 05 Hi Dale I also became interested in the RX mod you mention Before opening my 940 I decided to first check whether drain and source of the 2SK125 are symmetrical or not This was easy for me because I own a dead 940 RF board as a source of parts Page 34 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm for future repair of my rig I collected one of the 2SK125s from this board and built a source grounded test configuration with a 5K resistor connecting drain to 8V Then I fed a sawtooth test signal about 6 to 1V via 10K into the gate U drain was recorded against U gate on a DSO Tek 468 Thereafter I repeated the measurement with drain and source exchanged I obtained the characteristical FET response curves and these were exactly identical in both configurations This did not change when the test frequency was inc
44. 4 2006 http homepages ihug co nz jaking TS 940_02 htm Does putting the 2 2M ohm resistor where the 150 ohm Resistor should be make a difference Yes You bet Change the 150 ohm back to the direct circuit and the AGC responds very quickly similar to the AGC in a TS 930 AGC could not respond quickly before because it had to wait until C126 charged up This is in the heart of the AGC timing section Probably all TS 940s have R149 and R150 in the wrong place TO CHANGE THE RESISTORS Change around is easy You will need to take the IF Board out The difficult part is removing and putting all the connectors off on the board Before starting draw a diagram of the board showing each connector and position and colour of its wires That makes it certain you put the right connectors back in the right places If you don t draw a diagram you will not know where all the connectors go back Some two pin connectors could easily go in more than one place That s could be disastrous These colours are not shown in the service manual Page 50 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm I suggest you put in new resistors because with longer leads they will slightly easy to hold in place while soldering THE INITIAL PROBLEM SYMPTOMS ZL4AI discovered this while searching for the a fault described below AGC Only happens in SSB If T
45. 51 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 0 6 dB more insertion loss at 1 75 MHz 0 7 dB more insertion loss at 3 5 MHz 0 6 dB more insertion loss at 4 MHz through to 28 MHz This means the BA479 will reduce the signal and therefore will not improve the receiver performance In Jeff s opinion this is considerable increase in loss of receiver performance and not really viable to use a BA479 as a replacement Transmitter performance between 1 5 and 7 MHz will improve because of the much better BA479 IMD performance you describe On 31 5 2005 Thomas advised at 25 ma 3 I also tried a BA479G which I left from another project At 10 MHz and above the BA479 s have a slightly higher insertion loss than the original Kenwood diode 1 2 dB worse Below 10MHz the BA479 showed less insertion loss and were clearly superior with respect to intermodulation This means the only diodes that should be replaced are D13 D11 D9 D7 in operating at 1 5 MHz to 8 5 MHz and 25 ma D5 and D3 operate at less then 1 5 MHz and the performance of the BA479 is unknown in that region I wonder if you could document the actual insertion loss of a BA479 performance at 25 ma between 1 75 MHz AND 10 0 MHz I look forward to your reply Yours sincerely Jeff King Diodes on RF board Original
46. 9 I did not replace D3 D8 because these switch a frequency too low for the BA478 to be an effective PIN I checked the BA478 and found them to be good at frequencies above 2 to 3 MHz The BA479 have been offered in different versions and it is important to use those which are designed for HF not VHF Certainly other PIN diodes may also be useful The IMD of my 940 improved by about 5 dBm after this mod For re alignment of the receiver I mainly followed the instructions of the service manual for the RF and IF amplifier stages I did not align oscillator and PLL circuits I have a sweep generator Rohde amp Schwarz SWOB 5 equipped with log amplifier which was very helpful to optimise the bandpass filters on the RF board I established RX sensitivity with a HP8640B RF generator together with a home made audio voltage detector to determine an audio increase by 10 dB I have two of the HP8640B so that I am able to determine receiver IMD The HP8640B are quite famous since they produce a very clean RF signal and are sold at a reasonable price By the way I own two TS940 and use one of them for experimental modifications which are more critical so that I would not really recommend others to reproduce them If you are interested anyway I will report on that later It s past midnight now 73 for today Thomas gt From Jeff King lt jaking es co nz gt gt Reply To lt jaking es co nz gt gt To lt thomas_hohlfeld hotmail com gt
47. 940_02 htm On page 8 of the promotional brochure above its shows that the heat sink should run at or below 40 degrees Celsius REPLACE Q101 AND Q 102 ZL4AI found after replacing the original power supply transistors 2n5885 60 volt version with the 2n5886 80 volt version the heat sink temperature seemed to decrease MOTOR BEARINGS GUMMED UP TEMPORARY FIX Original Message From kenwood bounces mailman qth net mailto kenwood bounces mailman qth net On Behalf Of Garey Barrell Sent Friday 28 October 2005 4 48 a m To Bill Stewart Cc kenwood mailman qth net Subject Re Kenwood TS 940S Cooling Fan Problem Bill Stewart wrote gt I have a TS 940S s n 6040XXX which has a sluggish cooling fan on left facing front behind the power trans Sometimes it will not start I have shot WD 40 in it and tried to get oil to go down the shaft but sometimes it still won t start and if it does start it turns slowly amp erratically I measured the voltage to be around 18VDC with the fan disconnected and connected a fluctuating 5 to 1 5VDC with the erratic rotation gt Questions 1 Is this no load to load voltage drop normal gt 2 Does the voltage and fan speed increase with temp rise gt 3 If the above is a problem are there any mods to replace this fan or maybe make the fan run all the time gt The fan runs ok if it gets beyond the low start up point on a seperate DC supply gt Any comments will be appreciated thanks
48. CustomerSupportCenter Kenwood Corporation Japan URL http www kenwood com Email css kenwood co jp Page 52 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Original Message From Jeff King To Customer Service Section Cc k4oah mindspring com traian deck ro Bill Bailey Ken McVie Sent Tuesday March 15 20051 53 PM Subject RE Question about TS 940 R149 and R 150 Appear to be in wrong places Dear T Soranaka Thank you for your advice Could you please advise if it would be advisable to swap R149 with R 150 and vice versa so the TS 940 functions in accordance with the circuit diagram Yours sincerely Jeff King Original Message From Customer Service Section mailto css kenwood co jp Sent Monday 14 March 200510 29 p m To jaking es co nz Cc kcc amateur kenwoodusa com sabura tech kenwood com au Subject Re Question about TS 940 R149 and R 150 Appear to be in wrong places Dear Customer We are sorry for inconvnience I have checked with our communication department as to R149 and R150 Unfortunately reference number of R149 and R150 on the borad are reversed R150 and R149 are 2 2M and 68K or 150K respectively as shown in the Service Manual Yours sincerely T Soranaka CustomerSupportCenter Kenwood Corporation Japan URL http www kenwood com Email css kenwood co jp
49. D TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 73 Traian Belinas YO9FZS Original Message From Jeff King mailto jaking es co nz Sent Sunday 12 June 2005 5 34 p m To eduardo guisard com Cc Traian Belinas thomas hohlfeld Subject RE TS 940S Some few considerations Hello Eduardo Thanks for the email As you will see last year on your comments page I was very inspired by your discovery I was like many 940 owners very excited After doing the research on my web page I was disappointed to find that turning q10 allegedly made the front end unstable So for that reason I have not done that Have you any more information on turning q10 around I have turned q4 around on my radio In the end I am drawn between two view points 2SK125 FETs function the same in both directions as Thomas has measured so turning then m around makes no difference the scientific view to which I subscribe 2SK125s make a lot of difference turned around which makes the radio overload with the resulting gain Here is suggestion that you could carry out to prove your point and publish further If you connect the D S leads of the 2SK125 to a shielded lead and a switch so that the switch in one position is the normal factory setting and in the other position it is the PY1NR setting then you could swap the positions while listening to the radio and verify just how effective the reversal is You could report i
50. D reflector about their experiences with newer receivers and promised to summarize your comments and my tests for the group I m slow in getting this out because I lost some mail messages including my own but here s what I pieced together Comparison of Kenwood TS 940 to other Receivers This test is aimed at CW reception MY ORIGINAL QUESTION my own comparisons are at the end of the message As a died in the wool TS940 user I ve been believing that the 940 s receiver was as good as I could find for 160 and 80 meter DX CW short of some of the older rigs like the Drake and Collins stuff Even though copy is rough here in the black hole of DX I have been able to work a number of countries on these bands with just 100 watts Line noise at my place is MAJOR Then I visited N9QCT to see his new TS 570 on a trap vertical What I hear on the 570 amazes me It s early evening when all I hear at home on 160 M is static And his 570 is dragging in European signals above the background noise When he kicks in noise reduction NOT the noise blanker the CW sounds like it s a code practice tape On 160 Not only that but at the 50 hz filter bandwidth actually about 80 90hz there was practically no ringing I plan to borrow his rig and try it at my place with better RX antennas and the heavy line noise just to get an apples apples comparison So the question to recent buyers of new rigs is Compared to your experience with older top end rece
51. Europe UK K0BX Kenwood Interface HomePage 850 Repair Page K0BX Kenwood Interface HomePage Piexx Company Home International Radio Service Division http home fuse net jg Chips TS940Chip html QSL Net Index Yahoo Groups TS 940 Yahoo Groups Kenwood TS 950SDX AAvid The Defpom Kenwood Radio Modifications Page KENWOOD MODIFICATIONS LINKS XE1BEF PAGE K0CKD s Topband Kenwood Resources amp More The Kenwood Archives http www eham net reviews detail 239 http efjdevices net Problems html HELP WANTED More information on the Pin Diode Improvements would be appreciated PERFORMANCE COMPARISONS A lot of reviews found at http www eham net reviews detail 239 Page 132 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 133 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 134 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 135 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 136 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 137 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm TopBand Comparison of TS940 to newer receivers MEL CRICHTON_MELVIN_J LILLY COM Tue 15 Apr 1997 12 35 24 0000 GMT April 14 1997 A number of weeks ago I asked the TOPBAN
52. HF thru microwaves as platforms for transverters I quickly sold a FT1000D as not worth the money that 2 well modified 940 s could perform at I had a TS870 here on loan it has a great RX but very prone to overload on 40 thru 160 GL and 73 Carl KM1H 261 DXCC on 160 309 on 80 Comments from George Guerin K8GG 1 My experience with the TS 940 is it does not hear as well as the TS 930 or TS 950SDX Also there is generally a spike on the leading edge of the first CW character sent which risks grid damage to tubes like the 8877 8874 3CX800A7 etc 2 Your description of the TS 570 sounds very good Maybe they will make a TS 970 soon 3 I hear there are problems with the TS 870 because there are no filters at all except digital in the last IF This creates birdies in the pass band since it is at something like 14 or 17 Khz and a signal 28 or 34 Khz away can leak through I hear one W6 added filters and cleaned the birdies but Kenwood will not do this on production units so we will have to wait for a TS 871 or 880 4 I have used the FT1000MP and it does a pretty good job but I haven t put it side by side with other radios Setting the two DSP controls on the concentric rotary switches is a bit tricky The dual receive and or split is very good and easy A friend in Chicago says it hears better on CW than the FT1000D and the TS950SDX On phone I like the TS950SDX best but
53. KENWOOD TS 940 PAGE Version 2 4 April 2005 Version 3 25 April 2005 Version 4 27 May 2005 Version 5 31May 2005 Version 6 10 June 2005 Version 7 16 June 2005 Version 8 25 July 2005Version 9 30 July 2005 Version 10 4 August 2005 Version 11 13 Sep 2005 Version 12 18 October 2005 Version 13 23 October 2005 Version 14 22 March 2006 Version15 April 2006 From a passionate Kenwood TS 940 owner The 940 has to be one of the greatest transceivers ever produced This page is provided because Some information here is not available anywhere else and should be useful to any TS 940 owner Information does not exist in a single web site which is easy to follow If the information remains available more TS 940s will be repaired and functional and probably improved The intention is to acknowledge the person who discover the information so questions can be sent to that person When information is already well documented and reliably maintained on another site then a hyperlink is made to that site to avoid yet another slightly different version I will publish all email feedback at the end of the page so that whatever is discovered by others can be shared by all Please email to jaking es co nz Yours sincerely Jeff King ZL4AI DU7 Disclaimer No liability or responsibility whatsoever is taken for any of the information on this site You assume total liability for any modification you undertake Copyright Everything on this page
54. MI204 I tested these and found they are even a little better than the BA479 The problem with these is that they are hard to obtain Thank you for mailing the discussion on the reversed Q10 Q4 problem Although I was unable to find a difference in my test setup as I reported earlier it is certainly possible that there is an asymmetry of the internal capacitances that did not become apparent in my measurements I think I should try out this mod and do some measurements but it may take a little until I ll have time It would also be interesting to see how the increase in sensitivity if it really occurs will change the receiver s dynamic range Finally my congratulations for your exciting web page You did a very good job in digging out all the fascinating information about and around the TS 940 It s a pleasure to contribute Best regards Page 90 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Thomas DF5KF Page 91 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 92 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 4 5 Pin Diode Modification for TS 440 A similar sort of mod for the TS 440 maybe found at http www mods dk view php ArticleId 1709 4 6 So summary of Pin Diode Modifica
55. Phil Florig W9IXX arrl net Tue 09 Mar 2004 17 40 59 0500 Hi all I received the following e mail reference my inquiry on serial numbers for some of my Kenwood units This information seems to correlate with the information on the date codes of some of the components As you know there are usually Date codes on components The common way is to give a 2digit year and 2digit week EX 9340 is 1993 and the 40th week 8837 is 1988 and the 37th week As shown below my TS850s ser 60200208 is mfg in 1994 This is right as the component date codes are 9340 9409 9350 9410 and etc As shown below my TS940s ser 9100162 is mfg in 1988 This is right as the component date codes are Page 118 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 8817 8825 8837 and etc Bottom line is to check as many parts in the rig as you can to see the general date span I know that some parts may be older stock and some may have been replaced but the majority of the date codes should be within a year This will hold true for most medium to high production runs Hope this helps in some way Tnx agn guys for all of your inputs on this reflector and thank you Kenwood for answering my e mail request so fast We do appreciate it 73 Phil W9IXX gt Dear Kenwood Customer gt gt gt There is no sequence with our sertial numbers TS 850S s n 60200208 1994 TS 940S s n 9100162 1988 gt If you need further assistance please e mail us a
56. R 21 4v 20 5v Page 109 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm From Bill lt coorsbill y gt Date Thu Jun 12 2003 11 05 am Subject Re TS930S TS 940S Fan Low temp Mod All 930s and 940s were designed for the fan to come on almost too late in the interest of quiet operation that is until the 29v pass transistors go into thermal runaway destroying your drivers and the AVR unit in the space of about 30 milliseconds It s quite spectacular and I would not recommend missing it if it happens Alas to prevent this from happening and missing out on the fireworks there are two paths you can take One provide a circulating fan near the rig or behind it to remove the heat from the heat sink Two modify the circuit that controls the PS fan there are only two fans the PS and the PA or final unit with separate control ckts to turn the fan on sooner To do the latter unplug the rig for about a half hour to allow all the big caps to discharge Carefully loosen the AVR unit power supply regulator board to access the solder side Change R11 from 390 ohms to 470 ohms Can be 1 8w or 1 4w This will cause the power supply fan to come on at a lower heat sink temp You can test the fan by unplugging it from connector 11 on the AVR unit and then insert the leads of a 1K or so 1 4 watt resistor into the connector holes Then jumper 12v across the resistor positive to the center of the fan
57. S 940 left not running for a couple of days when you turn it on with the AGC turned off or set in fast position then the meter needle goes to up 25db 9 approx The signal is diminished like RF gain turned up Over the next 25 minutes the meter needle slowly moves it way back to S0 SSB in normal position and TS 940 turned on this does not happen Needle is initially at s0 During the first 25 minutes if you switch between off fast normal then the needle goes back to zero in less time say 20 minutes If TS 940 left for a couple of months and then turned on same behaviour but worse Meter needle goes full scale right in all positions off fast normal It takes longer say 40 minutes for the needle to move to the s0 then ts 940 functions as described above After R149 and R150 changed back to positions Kenwood intended in the circuit diagram the result was The fault of the rising S meter when cold disappeared S meter dropped back to S1 on both AGC OFF and AGC SLOW with no antenna signal Needed to adjust VR3 to bring the S Meter to S0 ACKNOWLEDGEMENTS TO PERSONS WHO HELPED SOLVE THIS T Soranaka Kenwood Japan was most helpful You will see in the emails below Kenwood have readily confirmed that these components are around the wrong way Then in a third communication above confirmed they are correctly installed Page 51 of 151 KENWOOD TS 940 PAGE
58. S SSB 135 dBm MDS CW cascaded 500Hz filters 137 dBm Sensitivity 10dB S N N 12uv Phase Noise 131dBc at 10 KHz Filter rejection CW gt 90 dB 2 tone dynamic range Wide 95 dB 20 KHz 2 tone dynamic range Narrow CW Filters 77 dB 2 KHz 3rd Order IP 1dBm at 20 KHz Wide Band transmitted noise 75 dB below full carrier The same TS 940 but with PIN diode mods to RF and IF boards MDS SSB 137dBm MDS CW 142 dBm Sensitivity 1uv Phase noise 131 dBc 10 KHz Filter rejection CW gt 90 dB 2 tone Dynamic Range Wide 102 dB 20 KHz 2 tone Dynamic range Narrow CW Filters 83 dB 2 KHz 3rd Order IP 5 dBM 20 KHz Wide band transmitted noise 90 dB below full carrier A few notes and comments Although the PIN diode improvement is evident in the numbers the audible difference First of all the receiver is noticeably quieter The IMD performance shows an appar about 10 12 dB under crowded band conditions This follows along with conversations Rhode several years ago when I first started using PIN diodes The cumulative effect The receiver is a pleasure to use in lowband pileups now The improvement in wideband TX noise is due to I believe the use of PIN s in those common to TX and RX on the IF board The stock diodes either generated noise or allo into the TX path The same appears to hold true in the opposite scenario This TX no was recently made aware of by a local on 6M and bears closer examination and possibl improvements The noise does
59. SSB power jumped to 100w but I still only had 3w or so CW The IC meter showed 4 amps with no output on SSB so I check the current with a ohm meter and verified it was around 1 2a A adjustment of the IC0 control fixed that With 100w Page 98 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm out on SSB the IC meter read over 16a The ohm meter read 8 5a to 9a Adjument of the IC meter adjust pot fixed that Then on a fishing expedition I look at the micro processor board and fixed several fish eyed solder joints no help but made me feel better Then under the Het Osc on the PLL unit there was a piece of black conductive foam that had deteriorated Also it had a green white residue covering it I cleaned all of it and removed the rest of the foam It helped alot I had to readjust VR2 back down to 110w or so and the CW output jumped up to 15 18w But still that is it on CW Thanks for all of your help Keith Spainhour KT4XW PLL BOARD 2 Remove the Wax from the VCOs From Garey Barrell lt k4oah gt Date Thu Oct 9 2003 1 49 pm Subject Re ts 940 Welcome k4oah Fred This is an indication that one or more of the PLL s are unlocked It will only get worse The two VCO s under the speaker two layers down of course are potted with a sort of beeswax Over time this wax becomes contaminated and the VCO s become unreliable I fixed mine by using a heat gun judiciously to melt the wa
60. Subject RE ts 940 Hi Jeff Thank you for the comments on the pin diodes Yes I used the BA479G These were quite inexpensive and it was easy to obtain them when I did this mod two years ago Today I checked for a source in the internet and found a German distributor who may still have the BA479G Check at http www schuricht de w3a default asp a button at the lower left will switch language into English They do not look too expensive 0 31 Euro when 50 are ordered I checked the BA479G with an RF generator and scope and found it to be good at 7 MHz and higher I am not sure if it is very effective at 3 5 Nevertheless I decided to replace D7 through D20 on the RF board I think I also exchanged D21 don t know any more but makes sense I did not change D23 and D26 in the preamplifier because these probably are already pin diodes and their exchange might impair the AGC characteristics There are some switching diodes also in the IF section of the 940 but I did not replace these because XF 1 already cuts the bandwidth at the front of the IF amplifier and there may not be too much intermodulation behind May be I will do this later when I have to take out the IF board for some other reason I told in my last mail that I did other mods in my 940s It may take quite long to describe them all so for the first time here is a short list Page 84 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm
61. Technical Topics explains what Pin Diodes were supposed to achieve Intermodulation properties of switching diodes by Dr Ing Jochen Jirmann DB1NV 4 3 Summary of Key points on Purpose of Pin Diodes by ZL4AI 4 4 Experience from Persons who modified the TS 940 4 5 Pin Diode Modification for TS 440 4 6 So summary of Pin Diode Modification PLL BOARD PROBLEMS Page 2 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm PLL BOARD 0 RESEAT CONNECTORS PLL BOARD 1 REMOVE THE BLACK FOAM FROM BEHIND THE BOARD PLL BOARD 2 REMOVE THE WAX FROM THE VCOS PLL BOARD 3 IDENTIFY WHICH PLL IS NOT LOCKED PLL BOARD 4 PLL BOARD AND RF BOARD AND PLL OUT OF LOCK CONTROL BOARD VOLTAGE REGULATOR HEATS UP AND CAUSES A SHIFT IN BFO ON IF BOARD AVR BOARD amp POWER SUPPLY FAN AND TEMPERATURES COOL AVR COMPONENTS BY REMOUNTING ON HEAT SINK POWER SUPPLY HEAT SINK RUNS TOO HOT VERIFY THERMISTOR 101 IS ATTACHED AND FUNCTIONING REPLACE Q101 AND Q 102 MOTOR BEARINGS GUMMED UP TEMPORARY FIX RF BOARD 1 BOARD RUNS VERY HOT HOW IT WORKS AM MODE HOW TO VERIFY ITS SWITCHED IN FM MODE SETTING FM CARRIER CW FILTERS SERVICE MANUAL amp SERIAL NUMBERS IDENTIFYING WHEN RADIO MANUFACTURED BULBS CONNECTOR PROBLEMS BATTERIES INTERNAL BATTERY REPLACEMENT INFORMATION NOT ANNOUNCED BY KENWOOD KENWOOD RELEASED INFORMATION S METER ALIGNMENT LEVELS PARTS LINKS TO USEFUL SITES HELP WANTED
62. That might help but toggling the front end on each over is a true pain Have fun 73 George MY OWN TESTS Side by side with TS 940 KJ9C gt From what I saw of my friend s 570 and from his comments the CQ article is on the money To switch antennas one must MANUALLY hit the ANT switch so that s one hit for transmit one to receive when using a beverage I have not yet looked for a transverter input on his rig as that is how my TS 940 s external RX antennas are wired when I get the rig at my place I will check for features but I know there is NO dedicated RX antenna input this would keep me from buying a 570 but I guess I could build an external TR switch like we built back in 1968 for club s S Line There is room for only ONE filter so decide whether it s SSB or CW 500 or 270 that s a big drawback but would not keep me from buying a 570 as I would likely go for the single 270 for IF protection but one in each IF would be nice I guess the TS870 has room for NO IF filters Written later I borrowed the 570 for a few hours and installed it with antenna switching next to the TS940 at my NOISY QTH line noise on some antennas as high as 20 dB over S9 In every case the 570 s noise REDUCTION unit did a better job of reducing noise and bringing up weak signals most tests on 160 and 80 meters where my noise is worst The noise blanker also worked but the
63. Volts too low 1N4739 output 8 31V at AVR terminal 6 pin 1 ie 0 31 Volts too high D9 only supplies the liquid crystal display and the remote control IC in Digital A it is very unlikely to have 0 5 watt drawn from it Very few 940s have the remote control chip installed My conclusion was it was best to leave in the original diode putting out 8 0 volts From Eham RE Kenwood ts 940s avr board Reply by N0XWR on February 28 2006 you won t find an AVR board for sale new you should endeavor to fix the one you have first check regulator Q103 it is in the rear left corner of the rig as the rig faces you it is on the heatsink for the power supply there are three regulators side by side it is the one on the far left no matter whether you replace it or it is good it is imperative that you cut the connector off of the three wire harness that plugs on to regulator Q103 and solder directly to it this harness comes from plug in 2 on the AVR over time the connector overheats and fails and cannot carry the 20 30 volts to and from that regulator i have seen the problem many many times when the connection to that regulator fails it takes out Q6 on the AVR board so check it next clif at AAvid now retired helped me get through the problem also check D3 D9 and D14 which are zener diodes on the AVR board they can be checked right on the board with a multimeter the board can be removed easily as you unplug the wiring harness use a sharpie and number each
64. a big part of available Rx dynamic range The PIN mods are usefull here in Eu 73 Traian YO9FZS All the Best Traian From Traian Belinas mailto traian belinas deck ro Sent Wednesday 22 June 2005 10 26 p m To jaking es co nz Subject Re pin diode reversed FET Jeff King wrote Traian Hi thanks for this It did really help my understanding In New Zealand we have max of 4 500 hams The bands are not crowded http kb9amg slyip com markd KB9AMG top_dx_spots by_callsign zl html This is the strongest ZL stations So on 80 meters at night I can tune whole band and only hear about 2 or more other stations My 80 antenna you have seen diagram is only about 13 5 off ground so it does not work well Usually I hear Australian stations and occasionally some USA Yes when propagation is there I hear those strong Russians here too Now back to Pin diodes My simple understanding of how the pin diode works is that the clean pin diode prevents other unwanted multiple frequencies up and down the band This would seem to be an advantage during transmitting because it prevents unwanted additional off frequency splatter signals on the band Until I read your email yesterday I did not comprehend to the fact that of course this works in reverse for receive It the existing diodes generate those off frequency signals then of course the a nearby signal will be picked up off frequency in reverse the same way and that off frequency signal will be heard as in
65. ad Legible versions can be obtained by emailing Kenwood It helps to point out there is considerable Health and Safety issue liability fro Kenwood if an Amateur using information makes a mistake because the information Kenwood provided could not be correctly interpreted S METER ALIGNMENT LEVELS Copied from W6NL Mods for the TS 930 PDF Clif Holland of Avvid a respected repairer of Kenwood radios emailed me to note that the Japanese specification for the standard signal generator used in alignment is different from the US signal generator calibration The 930 service manual refers to signal levels in dBuV so I had assumed 0dBuV was 1 uV and 40dBuV was 100uV But not so Clif is right and I m off by 6 dB I checked it out and although I see no mention of the issue in the TS 930 or TS 950 manuals I found a table in the TS 850 service manual pg 96 that confirms this It has two columns Japanese SG American SG 6dB 0 25uV 0dB 0 5uV 6dB 1uV etc 40dB 50uV etc Apparently the JA generator defines output in terms of open circuit voltage rather than voltage into a matched load This 6 dB difference affects the alignment of the RF PIN attenuator start point as well as the S meter settings for S1 and S9 Since the manual specs are 4 dB anyway the difference will be mighty small except for a more active S meter ZL4AI adds from page 78 79 of the TS 930 service manual confirms the above Japanese SG 0dB American 0 5uV from pag
66. ally The easy way to gain access to the PLL Unit is to remove the top two screws one on each side holding the front panel and loosen the bottom tow screws This allows the front panel to be tilted forward The speaker assembly and all the boards above the PLL unit may then be removed as a unit by removing only 4 screws and tilting this unit towards the front of the TS 940S No cables need be removed from the boards above the PLL Unit I hope the above information is helpful to you in dealing with the reciprocal mixing noise problem Thanks Rich Maher WZ4Z 1117 NW 7th St Boynton Beach FL 33435 RECEIVER 2 FIELD EFFECT TRANSISTORS AROUND THE WRONG WAY In September 2004 PY1NR announced he had discovered on RF board Preamp Q10 and on the IF board 2nd balanced mixer Q4 had been drawn on the circuit boards and mounted in the reverse orientation to that shown in the Kenwood Circuit Diagram See PY1NR web site www guisard com and Page 29 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm http www eham net articles 9261 Initially ZL4AI found it hard to understand this website and actually what PY1NR had discovered Starting with the circuit board layouts I tried to draw out the circuit What I found was that apparently the FETS were mounted with the drain where the source was supposed to be and vice versa As FETs normally allow current flow until the gate has a potential I wonder if this really ma
67. ame bulb as I did it s advisable that you not solder the 12 volt feed wire directly to the screw type base but rather wrap a couple of turns of non stranded fairly stiff wire around the screw threads instead Also be sure to connect the ground 12 volt feed wire to the screw base not the hot wire If the screw base on this bulb were to ever cut through the insulating grommet you might damage your set if the hot 12 volt lead were connected to it and then shorted the supply bus to ground You can easily determine which feed wire is hot and which is ground by measuring each with a voltmeter when the set is turned on The hot wire will have 12 volts on it and of course the ground wire won t Again make sure that the ground wire connects to the screw base shell of the replacement bulb The tip of the replacement bulb should be reasonably safe to solder the hot 12 volt lead to using the existing solder blob as a connection point do it quickly One other small caveat the 272 1143 bulb is just a tad too large to fit into the existing holes in the back of the TS 940S s meter but a few seconds with a tapered reamer resulted in the right hole size for a nice fit take your time and don t get carried away If done properly the original Kenwood bulbs can still be used later on if desired By the way it is necessary to remove the metal meter mounting bracket to perform this particular step but again the cost savings are well worth the small extra
68. apacitance feedback The gain obtained by inverting the D S for the TS940 Q10 may be still not high I don t intend to do it because of the reason explained before but the engineering feel tell us that something is not ok there And regarding the second mixer there it is obvious that it is not ok even if it works An counterexample is also the TS950 both SD and SDX which use the same Rx preamp as the TS940 with 2SK125 and 2SK520 they are all FET cascade preamps but for the 950 it is actually build as shown in the diagram no drain source inverting there maybe the same for their second mixer so which of them is the best regarding this the 940 or the 950 Please let me know if any other new info about the 940 950 Tnx 73 Traian Page 35 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm PY1NR provides feedback and re endorses previous statements on turning the FETs around PY1NRFeedback From ts 940 yahoogroups com mailto ts 940 yahoogroups com On Behalf Of John Rotondi Sent Friday 17 March 2006 10 51 p m To ts 940 yahoogroups com Subject ts 940 FET Reversal Fix Notes Dear Fellow TS 940 users Just a quick post to let others know this information which you can use as you see fit I have now fixed 2 TS 940SATs according to the findings of PY1NR who first detailed the reversal of 2 FETs in the TS 940 based on factory mistakes in the PCB silk screening After doing my own radio I absol
69. arrier To Noise Ratio Improvements 36 90 KB ASB0918A JPG TS 940S Squelch Switching Noise S N 711XXXX 85 04 KB ASB0918 JPG TS 940S Squelch Switching Noise S N 711XXXX 53 83 KB ASB0918B JPG TS 940S Squelch Switching Noise S N 711XXXX 65 29 KB ASB0921A JPG TS 940S SSB Talk Power Improvements S N 601XXX 708XXX 84 05 KB BOARD R118 as 4 7K between Q13 and L17 to C96 IF BOARD C8 Exists Exists Removed Exists Removed Removed Reason removed unknown Any information would be appreciated IF BOARD C9 Exists Exists Removed Exists Removed Removed Reason removed unknown Any information would be appreciated IF BOARD C10 Exists Exists Removed Exists Removed Removed Reason removed unknown Any information would be appreciated IF BOARD R220 Replaced with wire 105 Replaced with wire 105 Replaced with wire 105 Reason removed unknown Any information would be appreciated Page 127 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm ASB0921B JPG TS 940S SSB Talk Power Improvements S N 601XXX 708XXX 51 11 KB ASB0951A JPG TS 940S Erratic Display Remove The ROM Socket 84 33 KB ASB0951B JPG TS 940S Erratic Display Remove The ROM Socket 49 49 KB ASB0988A JPG TS 940S MFR 485 Driver Transistor Changes Blue Dot 79 27 KB ASB0988B JPG TS 940S MFR 485 Driver Transistor Changes Blue Dot 29 54 KB ZL4AI found that some of the diagrams Kenwood put on the web cannot be re
70. asurements before and after or _accurate_ noise figure measurements really wouldn t impress me that much since a receiver meeting the Kenwood specs would be limited by external noise regardless I suspect Garey is correct about the noise floor This is a less than 0 2 microvolt receiver Maybe turning the FETS around produces more noise which of course lifts the S meter but does it produce any more signal or better signal to noise ratio If first before an FET swap the S meter was calibrated against a signal generator then signal strength against independent signal source measured then an MDS measured then after the FET swap the s meter was again re calibrated then a reading of the independent signal sourceand separately MDS again would show that it was just not an increase in noise I wish Kenwood would behave like a responsible manufacturer and explain the technical reasons they do not recommend turning the FETs around Have a look at the following links which show how measuring receiver improvement is a difficult undertaking Even definition of what you are measuring requires some considerable reading and comprehension http www sherweng com table html http www rac ca opsinfo smeters htm http www seed solutions com gregordy Amateur 20Radio Experimentation SMeterBlues htm http www w8ji com receivers htm RECEIVER 3 THERE IS NO AGC TIMING CORRECTION STOP This modification was suggested following Kenwood Japan s advice that The I
71. ation and found that performance was degraded considerably when the PY1 correction was made They also mentioned that replacing one of the pair was not recommended The original circuit used a matched pair and they recommended replacing them only with a matched pair They were unable to describe the matching process but we surmised they selected for Idss and possibly transconductance The big question is these transceivers have been working and meeting specs for 15 years so who cares 73 Garey K4OAH Atlanta Original Message From Traian Belinas mailto traian deck ro Sent Tuesday 5 April 2005 9 34 p m To jaking es co nz Subject Re Ts 940 All problems SOLVED Possibly for you too Hi Jeff The website is and will be great Will look carefully at I have two things to say First is that the second mixer Q4 JFET is indeed wrong mounted Here are attached pictures you can use them on the website The PCB traces are symmetrical the mixer should be balanced and as the two FETs are identical type the way that they are mounted is obviously wrong As I said I have reversed the Q4 and the improvement exist but it is not so great as other had reported the sensitivity goes improved by 2 to 3 dB Page 31 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 32 of 151 KENWOOD TS 940 PAGE 5 14
72. ber 1994 In these articles he stressed that for receivers intended to have a very wide dynamic range the intermodulation distortion that arises from the use of unsuitable RF switching and tuning diodes imposes an important limitation He has recommended the use or substitution of such special purpose RF diodes as the Hewlett Packard HP5082 3081 PIN diodes Dr Rohde s articles encouraged Tom Thomson WOIVJ to investigate how bad in practice are the more distortion prone switching diodes and how good are those designed for low distortion Exploring intermodulation distortion in RF switching and tuning diodes QST December 1994 He carried out laboratory tests on four types of diodes The IN4153 generic PN switching diode the Motorola MPN 3700 PIN diode intended for RF switching the BAT 17 Siemens PIN switching diode and the low cost 1N4007 which is a generic 1 kV PIV rectifier diode with a PIN structure but not intended for RF switching He has tabulated results in terms of diode switch insertion loss dB at 1O MHz with 0 5 10 and 20mA bias currents and similarly the second and third order intercept points IP2 1P3 and dBm He draws the following conclusions RF specified PIN diodes are the devices of choice for low distortion switching at HF and above for band pass filter selection and C switching in a narrow band pre selector Although the presence of a PIN structure in the 1 N4007 makes it seem attractive as a low cost alternative to RF
73. ber of small low voltage lamps many of which will either fit directly or can be adapted to fit a bit of ham innovation is sometimes needed as displayed in George s piece Take a look into what Radio Shack calls their 12V micro lamp Cat 272 1092 It may well work as a replacement bulb for LCD displays and other situations where a very small size lamp is in order Hobby stores also carry what they call grain of wheat lamps which are very similar but be sure to ask about their voltage and current ratings By the way using a lamp rated at a higher voltage is fine as long as it will provide enough brightness once it s installed in fact it will last a lot longer than one rated at the nominal voltage Additionally if you lower the voltage to a 12V lamp even by just a couple of volts you ll increase it s life dramatically I ve seen test curves that prove that the life expectancy of a lamp zooms upward as the voltage across it goes down and vice versa of course Putting a resistor in series with each lamp that you replace will often give you two to three times the life expectency from a given bulb everything else being equal There are three things to consider before doing this 1 what value resistor will be needed 2 what its wattage rating should be and 3 how much loss of light is acceptable Lowering the voltage to the lamp will decrease its brightness and shift its color toward the red region so you ll have to visually judge whether you
74. connector so that you can reinstall it easily make a diagram too use small long nose forceps to mW 1W 18V 1 3W 18V D14 500 mW MTZ22JD 19 72v to 20 72v MTZ24JA 22 05v to 23 18v ZL4AI measured for diode marked 22D 22 8v DF5KF measured 22 7v Hitachi 1N4748 1W 22v 5 21v 23v Leshan 1N4747 20v 5 19v 21v Fairchild BZX85C22 1 3W 22V ZL4AI put in 1N4748 209 and measured at pin 5 21T on AVR see AVR_D14_replac Page 145 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm unplug the connectors to the AVR board Incidentally Q103 is part NTE377 available at mouser Q6 is part NTE382 also available at mouser i have the part numbers for the zeners if you need them 73s Jerry N0XWR ALC DELAY TIME This mod to your TS 940 will change the ALC delay time from approximately 1 sec to 0 022 second This means that the ALC will no longer impose its own time characteristics on your audio response the ALC will now follow your own sylabbic rate amd emphasis Usually the average power output will increase which will drive a linear amp harder at least those meters will swing higher The TS 940 has a 10uF cap C31 and 100k resistor R104 which make up the time constant for the ALC This tends to reduce the output power for the duration of the ALC time constant or till the circuit charges up again Then it starts all over again on the next word T
75. de mark store resulted in my discovering standard RS replacement bulbs of the exact size and shape RS Cat 272 1092 but the RS bulbs draw 15mA less or 60mA and they lack the little green bootie that the original Kenwood bulbs have The green bootie can be carefully removed from the old bulb provided it hasn t been cooked into place too badly and with the aid of a touch of clear silicone grease can be installed on the RS replacement bulb quite easily The 15 milliamp difference in current and light output is about the same as if one were to put a 47 ohm 1 2 watt bulb life extender resistor in series with the Kenwood bulb so to me it s perfectly acceptable The biggest difference is in the price 1 49 for two of the RS bulbs vs 4 19 each 8 38 total plus 6 00 shipping for the Kenwood relacements That s 7 19 per bulb from Kenwood 75 cents per bulb from Radio Shack Guess which ones I m using in the future What about the TS 940S s S meter bulbs does Radio Shack carry a replacement for them Yes but this time the difference is more pronounced The bulbs in the S meter are 12V at 75mA the Radio Shack replacement with wire leads Cat 272 1141 is rated at 12V but this time at only 25mA It s noticably dimmer than the stock Kenwood bulb but it may be acceptable to many you d have to try it and see Personally I chose to use Radio Shack s Cat 272 1143 a 12V 75mA bulb but with a screw in type of base If you use the s
76. e 51 of TS 940 Operating Manual If a standard signal generator SSG is available adjust VR 4 so the S meter indicates S 9 at 14 175MHz for a 40 dB 50uV signal from page 69 of the TS 930 service manual Page 128 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm SSG output at 14 175MHz 100dB u S meter reading S9 60dB 6dB This 100 dB u S meter maximum calibration information seems to be unclearly laid out in the TS 940 service manual but is inferred in the accompanying notes in the TS 940 service manual It looks like Kenwood s made a typo and missed it out The TS 940 Service manual on pages 72 73 is not very easy to understand ZL4AI have prepared the extended service instructions Red are items Kenwood missed out dBm values quite interesting to compare with other expert observations tahts S Meters are not linear To lt amps contesting com gt Subject AMPS s meter calibration From w7iuv nis4u com Larry Molitor Date Tue 13 Jun 2000 22 57 40 0100 At 07 45 AM 6 13 00 0100 Ian White G3SEK wrote gt According to the lab reviews in the magazines most modern receivers seem to be calibrated so that the difference between S9 and S9 20 is pretty close to 20dB Below S9 the scale looks linear but the dB per S point is not1 It typically takes many more dB to get from S2 to S3 than it does to get from S8 to S0 often less than 3dB per S point at the top end gt It doesn t have to
77. e 59 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 60 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 61 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 62 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 63 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 64 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 65 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm TECHNICAL TOPICS December1995 SWITCHING DIODES DJ2LR KA2WEUs REPLY THE ITEM RF Switching Diodes Controversy TT July 1995 included G4HRY s criticism of the advice given by Dr Ulrich Roinde DJ2LR KA2WIEU 4 in his excellent articles in OST that the second order IMD performance of several popular amateur HF transceivers could be improved by judicious substitution of PIN diodes such as the Hewlett Packard HP5082 3081 specifically intended as RF switching diodes I pointed out that the criticisms were based solely on RF losses and that G4HRY had not made any IMD measurements I added that I was sure that Dr Rohde could provide a convincing reply However in view of his experiences with GKPT s Omnii VI 1 felt it would be right to include G4HRY s view that
78. e soldered the plug bodies back into the board Before removing the connectors I sketched a simple schematic and labeled it and the plug connectors This enabled the return of the connectors into the original configuration without doing a lot of schematic wire tracing I removed all remaining old solder from the original plug bodies and solder connections then re inserted the male plug bodies into the pcb board I re soldered these parts back into the boards and while the board was accessible to the solder iron I used a jeweler s loupe and carefully inspected the solder points all over the board I pay special attention to the plug body pins for the numerous connectors on the board This process pays off big results I find at least 8 other connectors on this same board that are obvious cold solder connections the pins were obviously floating in the old solder and moved visibly when touched This discovery was very encouraging an obvious root cause of some of the intermittent issues this rig has had in the past I suspect that the loose plugs and many of the cold solder joints were actually caused by the WIGGLE and Plug Unplug technique so heavily endorsed in earlier internet comments and reports The first time it probably had good results over time this technique actually increased the amount of transceiver issues I reheated the solder on the connector pads that are bad discovering that the old solder would not stick to the plug body pins I
79. effort Page 120 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Moderator s note We ve all noticed how difficult it s become to change the pilot lamps inside of most of today s radios In the old days when radios and lamps both were a lot bigger changing a pilot lamp was a pretty straight foreword easily accomplished job The lamps were always mounted in sockets and usually just a twist of the wrist popped it right out ready to receive a new one Not so today most are now on small wires soldered in place and buried deep within the wiring of it s front panel It usually requires some internal surgery so many hams either don t bother changing them at all when they burn out or they leave the job for when the set has to be disassembled for some other troubleshooting reason George has offered some well thought out advise in his tips from above here s some more for you to consider What follows won t make the task of bulb changing any easier but it just might double or triple the time between pilot lamp failures When a lamp does burn out many probably think first of going back to the manufacturer for a replacement There s nothing wrong with that idea especially if it s a very specialized type of bulb But as George pointed out it s probably the most expensive and time consuming route to take especially when there may be a much more cost effective approach Since Radio Shack stores stock a num
80. ent http www kenwood net indexKenwood cfm do DownloadFile amp Document 2d13f766bec08d9297b46280e3758b9b95e42da53ae01ebf6db6adb98b2ed832baa0aa033a297d http www kenwood net indexKenwood cfm do DownloadFile amp Document d02a8b1ae4c8a39115ff83f169f65a1895e42da53ae01ebf6db6adb98b2ed832baa0aa033a297d1 TS 940S Signal To Noise Ratio Improvement With Noise Blanker http www kenwood net indexKenwood cfm do DownloadFile amp Document 09b9d746891ed0281dcc8482861e53da08bf66aab282a3fe0ec52cce1a1412bab3177362513310 TS 940S VCO Carrier To Noise Ratio Improvements http www kenwood net indexKenwood cfm do DownloadFile amp Document 57aa76a9447b3b37e1e9f60965f865a395e42da53ae01ebf6db6adb98b2ed832baa0aa033a297d http www kenwood net indexKenwood cfm do DownloadFile amp Document 2e0ca5ad0e0e9060f7f850fe27f80b1a95e42da53ae01ebf6db6adb98b2ed832baa0aa033a297d15 http www kenwood net indexKenwood cfm do DownloadFile amp Document 55221dd570b7e465e5087cf67f5e71fa95e42da53ae01ebf6db6adb98b2ed832baa0aa033a297d1 KENWOOD TS 940S RECIPROCAL MIXING NOISE In early March I Rich Maher talked to someone at International Radio regarding the reciprocal mixing noise problem with the Kenwood TS 940S I had been in the process of installing the fix described in your newsletter late 1986 issue and found that it had already been installed on my TS 940S S N 7100269 The factory installation had one problem the resistors used for R120 R129 were color coded for 900 ohm close enou
81. er which is 20700050 and it still had both mistakes in it so I hope this will improve on the already great recieve on the 940 73 and enjoy your improved TS 940S Dale KD5UVV In ts 940 yahoogroups com mikeferyok lt mikeferyok y gt wrote gt My friend and I did the R149 R150 swap and it improved the gain and gt noise level Adjusted the VR3 for a proper zero on the meter and gt worked LZ1YE and YV5YMA right after on 17 meters gt Very low noise compared to before the swap I highly recommend it gt Thanks to everyone here and Jeff ZL4AI Mike KC8ZNW gt I m still debating the transistor gain swap 5 Original Message From Articles eham net mailto Articles eham net Sent Sunday 24 July 2005 3 52 p m To jaking es co nz Subject Articles Improve TS 940 Receiver for Weak Signals Posted By KB9IV Well I finally got around to the AGC mod What a fantastic difference it also improves CW to my ears In addition the AGC mod also seems to improve useable weak sensitivity and decreases distortion Forget the FET reverse project NO difference here it s not worth the risk and time Best 73 Bill KB9IV Original Message From Bill amp Becky mailto wmarvin hickorytech net Sent Sunday 24 July 2005 4 00 p m To jaking es co nz Subject 940 AGC Change Hello Jeff Thank you for the info on the AGC correction What a fantastic difference here Page 44 of 151 KENWOOD TS 940 PAGE
82. ers really intended 30 July 2005 Abbreviated summary of key points in Emails from KI4NR Kenwood Repair Expert in USA When R149 and R150 are swapped around the AGC does not function as Kenwood intended The service manual is wrong on the schematic The silk screening of numbers on the circuit board are reversed to the schematic and wrong in relation to the Page 46 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm schematic only But the resulting resistor placement on the board is correct I believe the silk screening on the 940 IF board is correct and the IF schematic is wrong The 2 2 Meg ohm resistor is in parallel with C 127 the 68K or 150K resistor is in series with C 126 which gives the base line time constant when AGC switch is in the fast position This is the CORRECT arrangement The 2 2 meg ohm resistors in both the TS 930 and TS 940 sets up the bias to the FET from the 3 2 volt AGC reference voltage The 68k or 150k in series with the Cap set up the base time constant The other FET switch in for slow AGC on SSB and Fixed AGC on AM Also if you look at the TS 930 both schematic and signal board that has the almost identical AGC circuit R730 2 2M and R710 68K are the equivalent resistors on the TS 930 The TS 930 is the correct circuit in every way and the way Kenwood intended the AGC of the TS 940 to work
83. eu of the receiver of the 940 receiver section I am the owner of a 75A4 which I ve modified and updated over the 30 years I ve had the receiver and I find no other receiver comparable to it in many most significant ways So I would very much like to know how to connect the 75A4 into the TS 940S for use simultaneously with the receive section of the latter If this subject has already been covered in a previous newsletter please tell me how to get a copy ED Note Nothing published on this in back issues I m confused as to whether I need to cut diode 130 and 135 on digital Unit B in order for the Xcvr to operate over the same frequency range as the receiver Somewhere I noted that only diode 130 need be cut ED Note Kenwood Newsletter No 54 clearly states D135 is for MARS frequency only D130 is for Gen Cover age Transmit GEIL CHIP a chip available from Giehl electronics in Cincinnati that will slow the tuning rate to 2 khz per revolution on the main dial of a kenwood ts 940 Page 147 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm FEEDBACK FROM READERS Original Message From DGB mailto dwibos netnet net Sent Tuesday 5 April 2005 6 46 p m To jaking es co nz Subject Re Kenwood TS 940 Full description of AGC timing improvement which significantly improves receiver performance gt Excellent job on your efforts compilations Jeff 73 Dwight W9YQ Original Message Fr
84. experience which I humbly offer to the TS 940 user community Wishing you all good DX 73 John WA2OOB Ventura CA On Mar 19 2006 at 1 53 AM Jeff King wrote John found your report very very interesting Page 36 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Despite all the controversy some of which I have reported on http homepages ihug co nz jaking TS 940_02 htm I would appreciate if you could you please confirm you turned one FET around ran signal test identified improvement 1 S unit and then Turned other FET around and ran signal test identified improvement 1 S unit You know it would be helpful if Kenwood would actually confirm their view of whether the FET in correct position results in too much gain hope to work you one day and 73s Yours sincerely Jeff King zl4ai From John Rotondi WA2OOB mailto wa2oob earthlink net Sent Sunday 19 March 2006 11 56 p m To jaking es co nz Subject Re ts 940 FET Reversal Fix Notes Hello Jeff Very nice to hear from you Thank you for your interest in my posting on this topic I have seen your excellent website thank you for providing such valuable information to the user community I am still reading through all the information regarding PIN diodes and may mod my radio in that area as well Just a bit on my background I am a professional sound engineer and have been designing building maintaining operating professional music
85. f 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 9 Powered up the test source and tuned the TS 940 to it as before There was now another full 1 S unit increase in received signal level over the previous measurement giving 2 full S units total over the original base reading While this is probably not as sophisticated as if we would have used a Communications Monitor IFR Marconi etc or other test system directly coupled to the receiver with stepped calibrated attenuators and RF voltmeters coupled to the IF of the TS 940 we felt that it would be a fast way to have valid empirical data to verify that we had created an improvement rather than a disability for the TS 940 BTW post fix listening on air clearly showed the significant gain improvement In listening today on 10 meters on my own TS 940 I know that this additional gain has brought signals to the readable level that would otherwise have not been readable I have also done extensive listening tests with extremely strong local broadcast signals to determine if this fix has compromised rejection of extraordinarily strong out of band signals or has resulted in compromised receive RF or audio intermod or other non linearities resulting from component saturation imbalance or interstage distortion but have heard no such issues I will mention that my recently purchased IC 706 MK II for mobile use of more recent design and with some DSP total
86. f the Q408 output is switching from near zero to near TV value when changing modes from SSB to Am and follow that voltage trough that path down to the balanced modulator D78 and D79 have to be directly biased i e current shall flow through them when AM This mean they shall have 0 65 aprox voltage drop anode to cathode The current shall flow from the 15V line by the R277 R278 voltage divider to R276 D78 D79 R300 chain to GND You shall check the voltage at the R277 R278 and all of the R276 D78 D79 R300 parts and the respective trace FM MODE SETTING FM CARRIER From Traian Belinas mailto traian deck ro Regarding the FM power did you tried adjusting the VR9 on the IF board and checking the bias to the balanced modulator D73 VR9 settle the FM carrier ie FM output power as it is adjusting the DC bias unbalance to the D73 balanced diode ring modulator for FM Some of the TS940 VRs are very very touchy The power setting VR on the Control board and VR9 FM car are some of these I am sure you have observed that others have this behaviour I have found the 940 as being the most unstable radio from all of I had as the adjustments are very touchy and also need readjustment sometime or from time to time if you want constant trx parameters CW FILTERS Page 114 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm In ts 940 yahoogroups com Stjepan Nikolic lt snikolic gt wrote Hi all
87. gain gt gt Sincerely gt gt Kenwood Amateur Radio Customer Support gt gt gt Original Message gt From Philip Florig mailto null kenwood net gt Sent Saturday March 06 2004 9 22 AM gt To KCC Amateur gt Subject Feedback from Kenwood net gt gt Philip Florig would like the following help gt gt Hi gt The question has come up as to the meaning of the serial numbers used gt Can you explain the serial number system to me please I have 2 TS830 1 TS850 amp 1 TS940 gt Serial numbers are TS850 60200208 and TS940 is 9100162 Would like to know date of mfg and any other information gt Thank you in advance gt Regards gt Phil Florig gt gt Contact Information gt Email address w9ixx arrl net gt Call Sign W9IXX gt Phone 828 863 2048 gt Address 115 Horne Rd gt City Columbus gt State NC gt Zip Code 28722 Page 119 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm BULBS Ham To Ham 13 October 1996 73 s Ham To Ham column c o Dave Miller NZ9E 7462 Lawler Avenue Niles IL 60714 3108 Lighten up From George Vaughn WA4VWR comes this tip I ve found a local source for the bulbs that illuminate the Kenwood TS 940 s sub display When one of them went bad in my TS 940S I removed both and measured the voltage applied to and the current drawn by the single working bulb 12 volts at 75 milliamperes A trip to the local Radio Shack reg tra
88. gh to the 1K in the newsletter but in actuality measured 465 ohms Apparently Kenwood had gotten a bad batch of resistors from some supplier and had not discovered the problem At the time you indicated that was the first report you had received of the resistor value problem and recommended that I contact Kenwood I called them and was told that they had not heard of the problem before They also stated that a new fix for the reciprocal mixing noise problem had been developed and Page 28 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm was described in a Service Bulletin dated March 2 l987 I requested a copy of the bulletin and have attached a copy of it to this letter for your information See Issue No 76 Pg 30 and 31 for Kenwood Service Bulletin No 917 and schematics pertaining to this subject Since receiving the bulletin from Kenwood I have installed it on my TS 940S and found it to make a very significant improvement in weak signal handling in the presence of nearby strong signals I would recommend highly that anyone experiencing reciprocal mixing problems install the new fix It should be noted that some of the newer TS 940S have the fix installed I was preparing to install the fix on a friends s TS 940 which had a serial number 100 lower than my own and found that the fix had been factory installed Apparently more than one manufacturing site is used and serial numbers are given to each in bl
89. guy aol com mailto el34guy aol com Sent Thursday 23 June 2005 4 46 p m To jaking es co nz Subject agc modification Hi Jeff I was looking through the 940 page and found my feedback to you regarding the AGC modification with resistors 149 and 150 under the alc setting portion Im sure I mislabeled my original email to you on this think I wrote alc I am having some luck with changing out the 2 2 meg for a 1 meg resistor Im thinking maybe a little lower value might be worthwhile to test also like a 6 800k ohm value I know I received another email from you on this but I just wanted to let you know it looked like my feedback was in the wrong spot on your page Original Message From el34guy aol com mailto el34guy aol com Sent Sunday 12 June 2005 9 43 p m To jaking es co nz Subject Re alc mod Jeff I thought that mod might be a little better than it was for the alc It made my radio appear as if it was in fast agc mode all the time There wasnt a lot of smoothness in the ssb signal that Im used to Like I said maybe something like a 1 1 meg is worth considering in there There isnt much room to solder at all in there Geez its tight 73 Mark Editors Note ZL4AI questions the validity of these observations but has included them to keep feedback information unbiased Varying the resistors from Kenwoods values was never recommended or intended With resistors changed around on the Editors 940 AGC slow is still very much slower
90. he diodes in front of the filters diodes 3 5 7 19 which see the whole RF spectrum from by the antenna The forward current of these diodes is 25 mA in my 940 which appears quite a lot but probably was chosen because the diodes need to be very linear here The attached file 25mA all jpg shows the schematic test setup on top I already described it in my previous mail but this time I measured at a realistic diode current of 25 mA The two RF generators were set close to 7 3 5 and 1 75 MHz always 250 kHz apart The spectra figs 1 12 show the two carriers at the center All additional peaks are 3rd and higher order products indicating the non linearity of the diodes To get an ideal reference I also measured with the diode replaced by a wire bridge figs 1 4 and 8 Here the low remaining 3rd order signals less than 60dB reflect some non linearity of my test setup my homemade hybrid combiner may not be perfect As I already noticed in my earlier mail a general purpose diode 1N4148 produced a horrible spectrum of side products at all three bands figs 2 6 10 The original Kenwood diode 1S2588 was very good at 7 MHz and at higher QRG s not shown but worse at 3 5 and quite poor at 1 75 MHz figs 3 7 11 In contrast the BA479G was very good and provided the least side products figs 4 8 12 If you look closer at the distance of the carriers from the top graticule sorry background is quite dark you wil
91. he term PN junction And of course a PN junction diode will pass current a signal in only one direction characteristics but each side is doped differently than than a standard diode and in addition between the P and t doped specifically to allow the diode to switch VERY rapidly and this region is called the Intrensic junction thus Page 54 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm can switch is basically determined by the width of this Intrensic area the narrower the I junction the faster it will s frequency that you can pass throught it Unfortunately to build a PIN diode that will switch at HF freqs below 30 or the diode will switch too fast to allow one cycle of an HF signal to pass through it What all of this means is that PIN diodes are relatively expensive A regular PN junction diode typically a 1N4148 however a cheap true PIN diode will cost between one and three dollars apiece and thats why you do not see them ECONOMICS I m not sure why it took that much verbage to explain but it did Corsair II s used a regular silicon switching diode 1N4148 to switch the filters The Omni 6 does use PIN diodes b mentioned economics TenTec uses diodes that will do the job verses expensive PIN diodes I read Rhode s article on PIN diodes and decided I could improve the IM performance of my Omni 6 it didn t need Packard PIN diodes that Rhode stated were the best and installed them in my Omni
92. his procedure allows modification to the Control PCB X53 1420 11 in the TS 940 WITHOUT having to remove the PCB Remove the bottom cover and locate the Control PCB Locate R137 and R104 These are located in the upper right hand corner as the rig faces you upside down near VR3 A Service Manual would be very helpful for locating parts using a knife edge or similar carefully scrape off the insulation from the top of the two resistors Tack solder an 1 8 watt 2 2k ohm resistor from the top of one to the top of the other Put the cover on and it s finished TS 940 AVERAGE OUTPUT POWER SSB On the air conversations concerning a kenwood newsletter mod to change ALC delay time called for putting a 2 2k ohm across the top of r137 and r104 on the control p c b along with a 47 mfd cap between pin 1 and pin 2 of connector 8 on the control board The mod is excellent except 47 mfd is far too much instead use a 005 to 01 mfd to keep from over driving electrolytic not necessary but if used make sure nagative goes to shield wire pin Page 146 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm USE OF TS940S FSK RECEIVE FOR HF PACKET TS940S owners may wish to use FSK mode for HF packet FSK cannot be used for Packet transmit because the shift is 170Hz and Packet requires 200Hz shift This necessitates using LSB with AFSK I m not aware of any way to adjust the shift and 170Hz is required for FSK on AMTOR a
93. if I damaged it so better believe I was REAL careful with it and read the manual first But Greg seemed unconcerned that I was driving away with HIS 2500 dollar radio in my truck I set up similar to the TS570 test and as luck would have it the power company chose to temporarily fix the line noise after five months that day With all the mechanical and DSP features kicked in including a DSP59 on the 940 the TS940 and the FT1000MP performed about the same on 160 through the other bands CW only tests Some of the controls WERE tricky and the preset filters on the 1000MP took some getting used to There must be about two million bells and whistles on the 1000MP and my fat fingers found a few by accident It is an impressive rig but without line noise not enough to make me dump the old 940 Without the noise reduction the 940 is OK One thing I noted small point S meter readings were comparable for both rigs at low signals and noise levels but S meter readings were higher on the 940 for stronger signals of course that does not mean much as an S meter ain t that accurate just needed more attenuation with 940 I packed up the 1000MP and got it ready to take back to Greg about 8 miles from me then Indianapolis Power and Light came through just in time Line noise returned but only at S9 levels I quickly patched the 1000MP back into the setup and compared reception In this case with strong line noise the 1000MP was
94. ional plugs cause more attenuation than these pin diodes By the way I also measured the attenuation between the TS 940 antenna plug and the preamplifier input All frontend switching diodes plus the relay contacts plus the bandpass filters 14 MHz have an attenuation of 2 dB The same measurement with my Icom IC751 was 5 to 6 dB This shows that the TS940 is indeed an excellent construction Based on the results of my pin diode measurements I have now replaced most of the switching diodes with BA479G The only exception are D20 D18 D16 and D14 which I did not change With this change plus turning around Q10 the RX sensitivity MDS is 135 dBm an excellent result fully competitive with the top Rigs marketed today Best regards Thomas From Traian Belinas mailto traian belinas deck ro Sent Monday 20 June 2005 10 29 p m To jaking es co nz D11 1s2588 4 7 PIN type BA479 SI D 30V 50mA 100MHz D13 1s2588 7 8 5 PIN type BA479 SI D 30V 50mA 100MHz D16 15 1s2588 8 5 14 don t replace BA479 has 1 2 dB higher insertion loss than 1s2588 gt 10MHz D18 17 1s2588 14 20 don t replace BA479 has 1 2 dB higher insertion loss than 1s2588 gt 10MHz D20 D19 1s2588 2 30 don t replace BA479 has 1 2 dB higher insertion loss than 1s2588 gt 10MHz D21 1s2588 2 30 don t replace BA479 has 1 2 dB higher insertion loss than 1s2588 gt 10MHz D26 MI204 Pin Diode 2 30 don t replace BA479 has 1
95. it RF unit blackened but barely in the region of the transistors Q6 Q7 and Q8 armored rectangular area Already verify everybody the tensions and RF levels and is everything OK but the transistors are heating more than the normal one causing problems in the solder Soon after it link the radio the transistors and all the region in return already are with temperature above of the normal one Someone has some idea 73 Ronaldo Brisolla PY2NFE py2nfe uol com br HOW IT WORKS Page 113 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm AM MODE HOW TO VERIFY ITS SWITCHED IN From Traian Belinas mailto traian deck ro the CAR acts for AM and CW only For the AM and CW the balanced modulator is unbalanced also by CAR pot voltage by D89 for the AM and CW it is adjusted by CAR pot it is not a fixed value voltage D97 is an OR gate which supply the unbalancing voltage for CW or AM modes only the CAR acts for these modes only switched by the mode voltages at the Q410 and Q408 outs so by F and D CWG and AMG bias voltages respectively connector 12 contact 6 and 4 So you may check for the AMG voltage and switching Q408 When AM mode Q408 shall supply the TV voltage from connector 13 to the right side diode of the D97 then to the CAR potentiometer CV1 CV2 at connector 14 then by D89 to the balanced modulator and so unbalancing it and so introducing the AM carrier for the TX path So check i
96. it was unwise to put unquestioning faith in published articles including even those in OST and RadCom The detailed measurements provided by G3SBI TT November and those published by DB1 NV in VHF Communications showed clearly that there is a wide difference between different diodes used for RF switching both in insertion loss and in IMD performance and that IMD is significantly affected both by the forward current through the diode and by frequency As a result of an unfortunate delay the November item was written before I received a fax sent by Dr Rohde on July 18th This in a slightly abridged form reads I feel really concerned and sorry about G4KPT and the results of his experiments As a matter of record I would like to point out that intentionally 1 had not changed any of the diodes myself but had the authorised service departments of AES Milwaukee replace the diodes in the Yaesu FT890 ICOM changed the diodes in two IC765s and Kenwood made the same changes in a TS50 The itemised ICOM repair bill shows 0 12uV for 12dB SINAD I also had the other companies involved validate that following the diode changes the receivers were within specifications This validates my statement that this was a repeatable effort and the changes were not done at the expense of performance in any respect It is also a matter of record that the HP5082 3081 diodes were used in the production of the Collins KWM380 one of which I still own and whose noise figure is o
97. ivers like the 940 WAS ten years ago how do the new receivers stack up I know that audio DSP will overload without a mechanical filter as well and I saw it on Eric s 570 he has a 500 Hz filter on order But what about fully loaded TS570 TS870 FT1000MP Omni VI etc What differences do YOU notice AND THE SNIPPED REPLIES R4C about same as TS940 per AA1K I m a 940 user too in a high noise urban area 1000 feet from Amtrak line and major power transmission line etc but have an array of Beverages that help overcome the noise I ve not had anything newer here to compare with do have an R4C with Sherwood mods and find it about neck and neck with the 940 Also use a DSp 59 73 Jon AA1K Fixing the 940 from KM1H T aint nothing wrong with the TS 940 that a little work won t cure Mel Depending upon the serial number 8 Million a rough cut off there are many to some mods that really help Private E Mail me for specifics KJ9C NOTE MY 940 IS ONE Page 138 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm OF THE NEWER ONES SO THAT AIN T THE PROBLEM Also by changing about 45 diodes over to PIN s there is a dramatic performance improvement in RX performance I also use cascaded IRCI filters for both CW and SSB the Kenwoods have poor skirt rejection I have 4 940 s here that are used fm
98. jaking es co nz Subject TS 940S R149 R150 More Info Jeff I absolutely agree with the comments made by John KI4NR A rising S meter reading is due to a leaking capacitor and not the incorrect placement of R149 R150 In my case I did the resistor swap and noticed that the S meter s response was the same for both the AGC s Fast and Slow positions not good After undoing the resistor swap I now had the rising S meter problem a problem I didn t have before the modification In my case the problem was resolved by replacing C126 the capacitor that is in series with R150 2 2M as shown on the schematic Per John s advice I also plan on replacing C128 and C130 I must have one of those old IF boards because my S meter pegs when I turn the radio off 73 John WA3CAS THE PRODUCTION MISTAKE DESCRIBED Below is Page 92 of the Revised Service Manual Observe that R 149 and R 150 are mounted between almost the same connections I e between the junction of C127 R148 C128 C130 R156 to gt C126 Q21 Q22 The difference being that additional C 126 is between R150 and C126 Q21 Q22 Page 48 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Below is page 93 of the Revised Service Manual You will notice that R 149 is connected between C126 and the junction of C126 Q21 Q22 That is R149 has been mounted where R 150 should be Page 49 of 151 KENWOOD TS 940 PAGE 5 1
99. kes that much difference PY1NR suggest that reversing these transistors will provide 10 dB of gain But this claim does not appear be based on before and after measurement It would be useful to have some feedback on whether others have had much improvement by reversing the FETS Garey Barrell provides Kenwood s advice From kenwood bounces mailman qth net mailto kenwood bounces mailman qth net On Behalf Of Garey Barrell Sent Wednesday 9 March 20055 53 a m To Kenwood mailman qth net Subject Re Kenwood RE TS 940 What is the correct FET direction Jeff OK Just in from Kenwood Dear Kenwood Customer This information pertains to the TS 940S component location The circuit designer said the installation of Q10 in the actual TS 940S transceiver is correct The PCB view in the Service Manual is correct too The schematic is the only section that is in error The schematic indicates the drain of one FET connected to the source of the second FET The correct installation is to have the source of one FET connected to the source of the second FET In addition testing at Kenwood Communications in Long Beach CA showed poor results Sensitivity can become unstable The most important point about the Q10 pair is that both FET s must be replaced at the same time like a matched pair Replacing only o
100. l notice that the carrier attenuation of the BA479 is low at all bands and not much different from the original Kenwood diode Page 87 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 88 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Part 2 of my measurements will follow where I studied the diodes behind the input filters D4 6 8 20 and D21 which are run at a lower forward current The measurements are already finished but the figures need to be arranged Good luck for today Thomas DF5KF Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Monday 13 June 2005 4 31 a m To jaking es co nz Cc hohlfeld uni duesseldorf de Subject TS 940S pin diode part 2 and some other considerations Hi Jeff here comes part 2 of the pin diode measurements which concentrates on the diodes between the bandpass and the preamplifier of the TS 940 First a short comment on the 940 s front end when the RF has passed the RX bandpass three diodes follow before the signal reaches the preamplifier Q10 Of these two are switching diodes one of D6 8 D20 D21 while one D26 is a pin diode Only the two switching diodes are candidates for replacement For test purposes I assumed that D26 is fully open and D23 closed AGC at highest sensitivity In this case we deal with two switching diodes in series They are also in
101. light service they re often high brightness low life expectancy since flashlights are usually on intermittently There are charts available showing life expectancy at rated voltages for various lamp type numbers The lamp s manufacturer can provide this information and it s also sometimes included in the more complete electronic supply house catalogs It s surprising how much different lamps do vary in their average life expectations Dave NZ9E CONNECTOR PROBLEMS The following is the most sensible write up I have ever read about connector problems It is from the site below which contains other information and is well worth reading http www qsl net n5iw ts940 html Next I detached and then re attached each of the connectors mounted to the transceiver printed circuit boards Systematically I went over each of the boards carefully unplugging the connector inspecting and then reconnecting each one This process went routinely until I got to the main control board On this board the fourth connector checked pulled completely out of the board the male portion of the connector completely separated from the board leaving two very clean holes in the board I make a note of the faulty connector and continued checking plug connections The very next plug checked also pulled out of the board My inspection of the rest of the connectors did not yield any more problems quite so obvious I removed the board inspecting the faulty connection points and r
102. ly folds up from same broadcast interference that has no effect on the 940 The 940 receive audio quality remains exemplary I have been pleased with the results of the fix and feel it was worth the effort to realize the full potential of the original design intent I can only think that some amateurs did not have the same results because perhaps the FETs were not closely enough matched to begin with or they had other problems such as bad solder joints as often found in these units I hope this information is helpful to you And yes it would be nice if Kenwood would enlighten us on these issues but as the radio is not a current product and did quite well even with this defect they have little motivation to do so I will look forward to a QSO with you on HF 73 John WA2OOB Editors Note John has undertaken some very useful measurements and it is very useful to have some measurements Measurement outcomes could be more factual if a change in signal to noise ratio was measured by laboratory methods described by the ARRL For example MDS http p1k arrl org ehare aria ARIA_MANUAL_TESTING pdf http www arrl org ehare testproc testproc pdf If someone could do an MDS noise floor test before and after the FET swap it would be more complete evidence of the assumed improvement Page 38 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Garey Barrell sensibly advises Even a good test i e s n n me
103. m S8 75 dBm S9 70 dBm 10 60 dBm 20 51 dBm 30 42 dBm 40 33 dBm 50 24 dBm As you can see it s kinda poor at the bottom end but quickly stabilizes at about 5 dB per S unit With S 9 being within 3 dB of 50 microvolts and 5 dB per S unit this particular FT1000D has the best S meter out of the 10 or so radios I ve checked With a chart like this handy it gives you a real good idea just how good the other guys antenna is or how much gain his amp really has While the guy on the other end is usually an idiot and won t believe what you tell him at least you will know for sure Since it s so easy to do this I m surprised there aren t more folks with handy little charts for their radios I know not everyone has a room full of good test equipment But I bet most people on this list know someone who does or has access to it one way or another Give it a whirl you might be amazed 73 Larry W7IUV Page 130 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm PARTS 800 637 0388 www kenwoodparts com East Coast Transistor has an online data base with part numbers Very helpful in identifying the correct part They also supply some parts not listed on the database LINKS TO USEFUL SITES Kenwood_Japan Page 131 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Kenwood Corporation Kenwood Electronics Australia Pty Ltd Kenwood Electronics
104. mbled letters again Anyway what to do to fix The TS 940 has internal batteries which are similar to a CR430 3V lithium at 285 mAh Have a look at this page which explains battery replacement in an 850 http n6tr jzap com 850BAT html Genuine Kenwood batteries have metal tabs and leg pin wires on them and are soldered to the boards You don t need to use genuine batteries The table below shows many of the 3 volt dc coin type batteries you can use You can buy a CR2430 at Dick Smith or Radcliff If you want battery with legs which is easily soldered then go to Radcliff behind the Railway Station It will take you a week to get Maybe longer because they are unhelpful with finding small parts But they definitely can obtain special batteries Any way I brought a CR2430 and soldered wires onto it Wasn t easy to solder Then at Dick smith I brought two push on plugs with legs that can be soldered directly into a board similar to those used in later model Kenwoods http dse resultspage com search php sessionid 44202d9e016908da273fc0a87f9906b7 amp site amp w p2731 Model Number Capacity mAh Dimensions mm Weight g A B C D E CR 2016 RH 75 20 0 20 2 15 2 3 95 7 95 2 0 CR 2025 RH 148 20 0 20 2 15 2 4 85 8 85 2 8 CR 2032 RH 200 20 0 20 2 15 2 5 45 9 45 3 3 CR 2032 RH1 200 20 0 20 2 17 8 5 45 9 45 3 3 CR 2325 RH 190 23 0 23 2 17 8 4 85 8 85 3 3 CR 2430 RH 285 24 5 24 7 17 8 5 45 9 45 4 4 CR 243
105. n target with 0 3uV without a pre amplifier and whose 2nd order IMD is superior to other diode applications This should remove any doubts as to the correctness of my OST article 1 have had no experience in modifying an Omni VI nor did I do any measurements or modifications with it The ARRL edited in the Omni VI because it is a popular US made transceiver and there had been some discussion as to whether or not the European version had different diodes or relays Before fingers are pointed at specific diodes I would like to examine the circuit diagram because there can be no need to change all 40 diodes As an experiment 1 may want to supply one set of more modem diodes Everyone who has contacted me as the result of the OST articles had been advised not to use the HP 3081 for reasons of cost and availability but rather to use a Siemens BAR17 diode or M1204 diode which is available through ICOM dealers repair centres Those diodes are much less expensive and more readily available To the best of my knowledge the companies who changed the diodes in the equipments involved did not change the diode bias It is questionable why any one should wish to change diodes in the IF section similarly diodes in the transmit receive switches should not be touched Page 66 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Finally there is no question that relays provide the best of all worlds as far as IMD characte
106. n t gt quite sure when or what the exact reason was I just spoke to Ten Tec gt about this and they actually said they had tested different types of gt diodes to switch the Paragon s receiver filters and settled on regular gt switching diodes because there wasn t much difference with other types gt So I guess replacing the receiver filter switching diodes with PIN or gt other hot carrier etc types is probably a mod that some users have gt done themselves At least I know for sure it s not a factory gt modification gt Is there anyone out there who knows this for sure Has anyone done the gt aforementioned mod I know one fellow recently mentioned in a message gt that a rig he had for sale had the mod Now I ll go search for the Rohde gt article 8 gt 73 KE3KR Page 55 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 4 2 RadCom Technical Topics explains what Pin Diodes were supposed to achieve TECHNICAL TOPICS April 1995 RF SWITCHING I TUNING DIODES TT FEBRUARY 1993 REPORTED briefly an important article by Dr Ulrich Noble KA2WEU DJ2LR which was published simultaneously in English and German QST and CQ DL November 1992 on Recent advances in shortwave receiver design He subsequently published a series of three articles QST May June and July 1994 on Key components of modem receiver design and a recent follow up Key components of modern receiver design a second look QST Decem
107. nd RTTY It would still be nice to use FSK for receive the primary advantage being the availability of CW filters which are inaccessible in LSB mode By using the SPLIT capability you can use LSB for transmit and FSK for receive Tune in signals with VFO A on LSB Then press A B switch to VFO B enable FSK enable RIT and tune the offset to exactly 2 3KHz Then enable SPLIT When listening to signals depression of T F SET will allow you to listen alternately with each VFO the signal tones should be identical If they are not adjust the RIT on VFO B FSK mode until they are Optional CW filters are switched in by selecting the NAR narrow filters with the NAR WIDE switch LED indicates NAR I have found that this arrangement works quite well and enhances the readability of received packets especially under heavy QRM and fading It is easier to adjust the CW filters NAR WIDE and VBT in WIDE mode than the SSB Slope Tune controls I would like to hear from other TS940S users who have tried this technique or others that enhance HF Packet operation Send replies to WA1FMM W8AKF 73 Dan WA1FMM Thousand Oaks CA INQUIRY REGARDING USE OF ADDITIONAL RECVR I would be most interested in getting Information on how to use an additional receiver at the same time as the TS 940S is in operation receiving of course ED Note We covered adding another receiver to 930 Issue 59 Page 54 The User s Manual covers use of an additional receiver in li
108. ne FET at a time can affect sensitivity If you need further assistance please e mail us again Sincerely Kenwood Amateur Radio Customer Support 73 Garey K4OAH Atlanta From Garey Barrell k4oah mindspring com Sent Friday 11 March 2005 7 26 a m To jaking es co nz Subject Re Kenwood RE TS 940 What is the correct FET direction Jeff OK I just had a discussion via phone with the Amateur service department at Kenwood Page 30 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm The Q4 situation is not quite as clear The schematic appears to be correct sources tied together or push pull and the board layout drawing appears to be incorrect According to a tech in Japan the FET s in the actual unit are correct They have not found any instance where they were reversed in the actual radio or any in house docs that could have resulted in such an error I guess someone is going to have to open one up and look at the traces Looking at the board traces in the component layout it certainly appears that one FET has the Source and Drain connections reversed if the FETs are installed in the orientation shown Perhaps the board traces were changed ZL4AI editor comment Boards made exactly as shown in the Service Manual The guys at Kenwood both in LA and Japan are pretty frustrated with the whole mess They tried to duplicate the Q10 situ
109. not change dB levels when going from full power to the transverter port so it can not be blamed on thermal noise in the subsequent linear a Magazine reviews of the TS 940 were of early production Kenwood at first refused to problems They then went thru two different mods before they were satisfied The imp and late models is about 15 dB Serial numbers in the mid 8 Million group and up had factory mods Kenwood Service Bulletin 917 may be retrofitted to the earlier radios It is a fairly simple mod Other KW radios such as the TS 850 and TS 930 could also benefit from PIN mods They ports and are quite reasonably priced on the used market I cant speak for other brands but a quick review of a few Service Manuals shows an a across all brands with respect to diode switching schemes 73 Carl KM1H Submissions wsvhf qth net Subscription removal wsvhf request qth net End forwarded message Original Message Page 82 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Wednesday 27 April 2005 10 42 a m To jaking es co nz Subject RE ts 940 Hi Jeff thank you for your reply and congrats for the informative web site I read about the PIN diode mod in a web message I replaced diodes D9 through D20 of the RF board by the PIN types BA47
110. notice the diff in rcvr sensitivity The noise Page 139 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm blanker on the OMNI is about as effective as any but I don t think it is better than the 940 re noise blanking But Yes the front end does not Block in the presence of a loud signal next door The second reason that I went for the OMNI is that it s signal on CW QSK at high speed is distinctly better that anything else save the Icom 781 that I ve heard anywhere else The fact that you can cascade filters on the NEW OMNI PLUS really makes me twitch I ve already signed up to do the full upgrade to my radios I have a 500hz RTTY filter in the 9mhz path after the mod I ll be able to have a choice of the RTTY filter or the CW filter I think that is a real advantage Of course stacking of filters is pretty nice on the FT1000 stuff too The OMNI operation is pretty intuitive too it has less bells and whistles but I can t think of any I miss from the old 940s Remember that 98 of my operation is CW and RTTY de joe comments from K3SME Were you able to borrow the rig and try it at your QTH I have found that 160M performance is very QTH specific I have borrowed goodies like DSPs which knocked noise down ALOT at my buddy s QTH but didn t do much for my noise here as an example One of the locals
111. now whether this will help to reduce the BFO shift of your rig during warm up It is interesting that the service manual says that D14 is either an MTZ 22 or an MTZ 24 type legend below the AVR schematic page 103 It seems therefore that Kenwood has also tried different diodes here One of my 940 rigs is presently open so I did a few measurements The voltage across D14 is 22 7 V At Pin 21T of the AVR unit I have 21 2 V It appears thus that my TS 940 has the MTZ 22 diode It may be interesting to you that despite the lower 21T voltage I had to replace Q6 a couple of years ago I chose a standard NPN type in a TO 220 case This one gets only a bit more than handwarm and there were no problems any more In addition to Q6 other parts on the AVR board also become quite hot for example C12 after a couple of hours I found that diodes D10 D13 are the reason They dissipate a lot of heat to the board which turned dark below the diodes and to other parts such as C12 I removed these diodes from the AVR board connected an appropriate bridge rectifier with sufficiently long wiring and mounted this rectifier on the black heat sink D1 and D2 ran also hot and were moved to the heatsink as well This has helped C12 remains cool now Best regards and 73s for today Thomas DF5KF ZL4AI ran the TS 940 for two hours and turned it off 76 is far too hot to put your finger on Something could be seriously wrong in the Has been replaced with Measured
112. nsertion loss moderately increased below 7 MHz reaching 3 dB at 3 5 3 I also tried a BA479G which I left from another project These produced very low intermodulation signals even below 2 MHz which surprised me At 10 MHz and above the BA479 s have a slightly higher insertion loss than the Page 86 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm original Kenwood diode 1 2 dB worse Below 10MHz the BA479 showed less insertion loss and were clearly superior with respect to intermodulation To summarize the BA479G is better than the original TS 940 diode only at frequencies lower than 10 MHz As you will imagine I am thinking about returning to the original diodes at 10 MHz and above It may take a couple of weeks until I will have time I can also take some digital photographs of the intermodulation spectra and mail them to you if you are interested may take 2 3 weeks Let me know if your e mail server has limitations in file size Best regards for today and vy 73 Thomas DF5KF Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Friday 10 June 2005 8 56 a m To jaking es co nz Subject RE BA479 etc Hi Jeff thank you very much for including these excellent articles on the web page It s so useful that I ll print it out Now here is part 1 of my measurements on the RF properties of the 940 Front end diodes To start I concentrated on t
113. ny many 940 I have repaired new and old serial numbers and have not found one yet that had the resistors in wrong Look at the TS 930 schematic to see what I am taking about 73 John KI4NR Editors note On the TS 930 signal board the equivalent AGC resistors to R150 and R149 are R730 2 2M and R710 68K Original Message From LPC Wireless KI4NR mailto lpcwireless cfl rr com Sent Friday 29 July 2005 5 39 a m To jaking es co nz Subject More Info Your 940 observations Page 45 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Jeff I forget to add something When you swap the resistors around you are putting the 2 2 Meg ohm in series with C 126 this effectively removes the Base line time constant to all AGC positions on the switch including AM even thou the switch does not function there That why people say the meter is more jumpy plus the 150 K or 68 K bias the gate of Q23 more heavy and allows the receiver to stay more sensitive to low level signals if you look at the TS 930 schematic this is the correct circuit in every way and the way Kenwood intended it to work and how the 940 is One other thing on all the older 940 4 5 and early 6 mil serial number the IF board is different The gain distribution in not the same All the 940 late 6 and newer had better IF boards They have more gain TX amp RX the radio are hotter sensitivity wise better AGC compression I use a
114. ocks Consequently it is possible for higher serial numbers to be produced at one location without the fix while another site any have cut in the fix but is using numbers from a lower block The quickest way to verify whether the fix has been installed is to check R120 and R129 on the PLL Unit X50 2020 00 If these two resistors are 3 3 ohms in value Editor correction Service Bulleting 917 says 3 3 Kilo Ohms the fix is already installed Do not depend on the on the absence of C176 C180 or C181 as an indication as earlier attempts factory or field to correct the mixing noise problem may have removed these same capacitors The instructions in the bulletin state that when making the modifications to the RF Unit X44 1660 00 it is easiest to move C132 C133 to the foil side of the board As the component side of the section of the RF Unit containing these two capacitors has been filled with wax it is definitely not easier The factory installation of the fix left C132 C133 on the component side and installed the R154 C193 and R155 C194 series RC networks on the foil side This is definitely easier As a side note the installation of the fix took me about 2 hours Both the PLL Unit and RF Unit modifications must be completed before the transceiver is usable If you install just the PLL Unit modifications and then try the receiver CW signals will should like raw AC Also to make life simple do not remove each of the boards above the PLL Unit individu
115. om Curtis Benjamin mailto benjamic michigan gov Sent Wednesday 11 May 2005 1 39 a m To jaking es co nz Subject Thanks Jeff thanks for setting up the TS 940 page I hope it takes off and becomes the spot for 940 info Curt Original Message From Ed mailto ca urso2 verizon net Sent Monday 23 May 2005 7 18 a m To jaking es co nz Subject TS 940S Reciprocal Mix Noise Mod Correction Jeff Congrats on your fine TS 940 Web Page Keep up the good work I wish to point out a text error in the letter from Rich WZ4Z regarding resistors R120 and R129 in the PLL Unit which should be corrected to 3 3KOhms each NOT 3 3 Ohms as stated This refers to a Kenwood fix given in their Bulletin 917 dated 3 2 87 Also your AGC Timing Correction was applied on my rig SN 806XXXX and worked great Sure enough resistors R149 68K on my equip and R150 2 2Meg had been incorrectly installed by the Mfr The board markings for those resistors were wrong I am also following with great interest the developments regarding FETs reversals noted by PY1NR Page 148 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 73 Ed Alves KD6EU USA Original Message From EL34GUY aol com mailto EL34GUY aol com Sent Thursday 2 June 2005 3 37 p m To jaking es co nz Subject ts 940 stuff Hi Jeff Im getting my first 940 hopefully sometime next week Ive been reading your website and it has some
116. out scheme for the 950sdx is below ZL4AI found this system did not work for his TS 940 which was manufactured in 1986 and began with 6 A good idea is to Take covers off and look at the IC chips Use the date scheme code below W9IXX email to confirm when the parts were made Page 117 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Kenwood TS 950sdx serial number Bill Martin k4sgf k4sgf net Sun 27 Jan 2002 20 22 07 0500 Mine is 01100190 so guess that makes it November of 98 right Bill K4SGF Original Message From NR1DX To k d wilson ntlworld com KENWOOD Sent Sunday January 27 2002 3 01 PM Subject Re Kenwood TS 950sdx serial number Kenwood serial number decoder XYYZZZZZ X 2 last digit of the year YY Production Month ZZZZZ sequence in production for that month So Kenny yours would have been the 7th unit to be produced in April of 1998 the 950SDX wasn t in production in 1988 I m told that this applies to all Kenwood rdaios manufactured in at least the last 20 years maybe longer I wonder what the last official serial number was for the 950SDX Mine is a 00900014 Anybody out there with a newer one Dave Nr1DX At 07 02 PM 1 27 02 0000 k d wilson wrote gt Hi Gang gt The serial number of my TS 950sdx is 00400007 can anyone please tell me gt what year this is gt 73 de Kenny M1HAM M5RIG Kenwood Fwd RE Feedback from Kenwood net re serial numbers
117. pment I welcome comments from sceptical readers or those spotting printing errors etc Fortunately there is good evidence that the vast majority of 7T items do work as intended and often provide useful additions to amateur lore Intermodulation properties of switching diodes by Dr Ing Jochen Jirmann DB1NV ZL4AI was contacted by a neighbouring ham known for many years Peter Johnson ZL4LV peter Johnson Paradise Net Nz Peter designed and developed from scratch in the early 1970s an HF transceiver Actually it is still under development and may soon have BA479s installed The local Branch of the New Zealand Amateur Radio Transmitters Association under Peter s guidance sold this as a kitset Peters design was the first use of diodes for band switching Peter published this technique in English Radio magazines the early 1970s and thereafter the first commercial transceivers appeared with diodes switching bands As the inventor of the concept Peter has collected articles on diode switches and provided the following Page 67 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 68 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 69 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 70 of 151 KENWOOD TS 940 PAGE 5 14 20
118. r gt gt The supplier advises they have the BA479 but cannot tell if it is a G or S gt I have asked them to put a resistance meter on it and await those gt results They replied they could not help gt gt Attached you will find the datasheet As you can see on the second gt and third lines on the first page gt Reverse impedances are gt G 5 k Ohms gt S 9 K Ohms gt gt It appears to me that the S might be better or no worse than the G Page 85 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm gt gt Do you think S would be suitable to use without further testing gt My worry is installing an S and finding it does not work well gt gt I have an interesting article from Radcoms Pat Hawker on Pin Diode gt replacements in July 1995 If you would like this I will send that when gt I have it scanned This article explains that the BA482 replaced in the gt Omni VI with the HP 5032 3081 resulted in impaired performance because gt the HP put through 0 5 dB less signal gt gt gt Your sincerely gt Jeff King Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Tuesday 31 May 2005 9 15 a m To jaking es co nz Subject BA479 etc Hi Jeff Thank you for your mail and your thoughts on the PIN diode mod Yes you are perfectly right in that this mod will probably be a tradeoff between linearity and a slight loss of sensitivity I would be
119. r side of the TRX Best 73s for today Jeff Thomas DF5KF gt From Jeff King lt jaking es co nz gt gt Reply To lt jaking es co nz gt gt To thomas hohlfeld lt thomas_hohlfeld hotmail com gt gt Subject RE ts 940 gt Date Fri 27 May 2005 19 35 16 1200 Your mod 4 is also very helpful for me I have heard about a TS 940 that is supposed to have this problem of frequency drift after operating for 30 minutes It apparently shifts frequency slightly then jumps back Just sometimes comes and goes Sounds like you have solved the problem Wow thanks Can you please tell me which regulator was it that you shifted to the heat sink gt Your sincerely gt Jeff King Original Message Page 101 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Tuesday 31 May 2005 9 15 a m To jaking es co nz Subject BA479 etc You also asked for the IC that warms up my mod 4 I believe it was either IC7 or IC6 on the control board but I am not entirely sure Next time I open my 940 I will see and let you know Warming up of the IC caused a slow shift of the 100 kHz BFO L19 Indeed L19 was quite sensitive to changes in temperature in my 940 Perhaps you should verify with a counter that the jumps in frequency you mention are really caused by this BFO Best regards for today and vy 73 Thomas DF5KF Original Message F
120. rch 2006 11 44 a m To TS930S yahoogroups com Subject TS930S 940 clock display stopped working Good day all I recently got hold of a Kenwood 940 Fine audio on the radio compared to the previous one I have the 440 and very nice although heavy transmitter I have only been using it a couple of weeks and the other day the green display that shows the clock and split freq s which was working fine up until then had some 0 s in the display as well as some symbols when I turned it on I shut it off and put it back on and the display has been blank ever since Any ideas as to what the problem may be Could it be the clock battery I don t know when or if the radio last had it s batteries changed but I wouldn t think a clock battery would go so fast I don t know Any thoughts ideas or suggestions would be very much appreciated Thanks JIM ZL4JB BATTERY REPLACEMENT From Jeff King mailto jaking es co nz Sent Wednesday 22 March 2006 5 16 a m To Jim Bazsika Subject RE TS930S 940 clock display stopped working Jim Page 124 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Definitely the battery behind the LCD has lost voltage Almost exactly same happened to my 940 What I found was voltage on this battery had dropped to 1 7V Should be 3V found if I left the 940 24 hours the battery recovered up to 1 8V and the sub display worked for about 20 minutes and then became scra
121. reased to 10 MHz It seems therefore that the 2SK125 is symmetrical As a consequence i decided not to correct the layout error in my 940 Like others I also believe that there is not much to improve My 940 has an RX sensitivity of about 0 15 V 10 dB S N on all bands well I must say it was worse until I re aligned the entire RX The IP3 is 18 dBm I once replaced the band switching diodes by PIN diodes Like others I often had connector problems after working in the 940 another reason only to go into this rig when necessary Best 73 Thomas DF5KF THEN TRAIAN PROVIDES MORE OVERVIEW Original Message From Traian Belinas mailto traian deck ro Sent Friday 29 April 2005 2 05 a m To jaking es co nz Subject Re FW ts 940 Regarding the TS940 2SK125 preamp yes the FETs have this interesting feature for low signal low freq and or low DC they are symmetric This is why they are used as passive variable low resistance attenuator switching for low signal with rather good results The things are changing at HF VHF amplifiers where the interelectrode capacitances became important do you remember about neutralising a FET preamp and these are not quite symmetrical as the devices are manufactured so that the drain to gate capacitance to be as low as possible for obtaining lower out to in feedback when used for common source applications So even if symmetrical why to use it as for having the greatest unwanted out ot in c
122. reduce the voltage drop on IC s on the Control Unit via AVR Unit thru reduction the signal 21T from 23 2V see service manual page 103 to 21 V May be the name of the signal has a sense To drop the voltage we shall use D14 with 22 V or a bit less U i o IC7 23 2 15 8 2 V 21 15 6V 6 8 2 100 73 So we would have a 27 reduction the dissipated power from all the 3 voltage regulators in Control Unit Additional advantage of my suggestion is the Q6 will not blow when AC 220 Volt is low It is happened in winter time in Russian country side due electrical heating of houses When AC 190V the voltage drop on Q103 too low it current amplification is low beta is function from emitter collector voltage due that Q6 is trying to give more drive to Q103 till Q6 had burn with D14 I have changed two times Q6 with D14 by the conditions Page 105 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Best regards Jeff and Thomas Victor UA2FP Kalinigrad 27 September 2005 Original Message From thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Sunday 16 October 2005 9 44 a m To vic_kz mail ru Cc jaking es co nz Subject RE Fw TS940 Mods Hi Victor hi Jeff sorry for the late reply I had to visit a couple of conferences during the last days Victor s suggestion to reduce the 21T Voltage from 23 to 21 Volts bringing down the heat production of IC7 makes perfect sense to me Let us k
123. ristics are concerned but not necessarily the best solution in terms of space and costs 1 have just tested a soon to be re leased transceiver which uses PIN type di odes and exhibits superb IMD characteristic while maintaining a good noise figure As to multi tone functionality once 2n and 3rd order IMD tests have been done on can predict the higher order IMD effects especially since they are based on diode characteristics and this type of test is a legitimate test to evaluate receivers Hopefully your readers will not deduct from this experiment that QST or other reputable magazines publish articles which are technically incorrect In a subsequent letter dated September 19 1995 Dr Rohde confirms that he has run into a lot of people who have modified their RF switching diodes and have been extremely happy with the results Further after refining his test set up he finds the improvement is now slightly more dramatic than outlined in his QST article In regard to Dr Rohde s endorsement of the technical accuracy of articles I would enter a caveat While most writers strive lo complete accuracy the mechanics an Murphy s Law of publication make it difficult to avoid some errors particularly in column produced to a tight deadline Many years ago I stressed that I regard Technical Topics as forum for new ideas not all of which are likely to prove repeatable or even strictly accurate No guarantees can be given on experimental ideas still under develo
124. rom thomas hohlfeld mailto thomas_hohlfeld hotmail com Sent Friday 10 June 2005 8 56 a m To jaking es co nz Subject RE BA479 etc As my TS940 is open now I had a look which of the voltage regulator IC I had moved back to the heat sink It is IC7 on the control board next to relay RL2 I include an additional jpg file which shows upper figure the place on the control board where I replaced IC7 by a connector with the three cables leaving arrow The lower figure shows the voltage regulator at its new place arrow The heat sink needed to be unscrewed in order to drill a hole for mounting IC7 I mounted IC7 isolated from ground If you decide to do this mod be very careful not to make any mistakes The primary 22V line may cause severe damage when connected to the 15V regulator output Page 102 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 103 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Good luck for today Thomas DF5KF See also COOL AVR COMPONENTS BY REMOUNTING ON HEAT SINK Below AVR BOARD amp POWER SUPPLY FAN AND TEMPERATURES eHam net Forum Elmers Kenwood TS 940s Forum Kenwood TS 940s Reply Anonymous post on February 19 2001 Can someone help My fan in back of my TS940s has developed annoying rattling sound nothing appears to be loose Is there any quick fix to this problem Thank you by AL7BB on February 19 2001
125. series with respect to their forward current which is determined by R31 I measured 17 mA in my TS 940 The impedance which these diodes see is also important I estimate it about 50 Ohm because the bandpass filters of the TS 940 are constructed symmetrically Therefore my test setup was similar as before with the following changes 1 I tested two diodes in series 2 I used a forward current of 17mA and 3 I also measured at 10 1 MHz Because the 1N4148 was so poor in part 1 I did not consider it further The attached jpg file again contains a plot of the test setup Here are the results see attached jpg file At 10 1 MHz figs 1 3 the original Kenwood switching diode 1S2588 is as good as the pin diode BA479 The same also applies to higher frequencies which I do not show here The insertion loss of the two BA479 in series is slightly higher than that of two Kenwood diodes but is still less than 1 dB more on this below At 7 MHz figs 4 6 the 3rd order products are clearly increased by the Kenwood diodes fig 5 in comparison with the reference diodes shorted fig 4 The BA479 fig 6 is clearly better than the Kenwood diode although a minimal increase is also seen compared with the reference At 3 5 MHz the Kenwood diodes generate a lot of intermodulation products fig 8 and the BA479 fig 9 is obviously superior The same is true for the 1 75 MHz band figs 10 12 In summary the BA479 is better than the original Kenwood
126. specified PIN diodes its insertion loss performance When unbiased and reverse biased and its IMD performance when unbiased is demonstratively interior to RF specified PIN diodes He adds The manually switched and tuned front end filters of the 1960s and 1970s had much to offer in terms of second order IMD but we need not retrogress to those techniques to achieve improved 1P2 and 1P3 performance today More attention paid to front end filtering in general can produce the improvement we need Dr Rohde in commenting on W0IVJ s finding notes that many amateurs had reported difficulty in obtaining HP5062 3081 diodes He recognises that even with the Motorola MPN3700 with a US price Of less than 11 replacing all 20 plus filter switching diodes can be expensive Nevertheless he recommends changing all the diodes between the antenna and the first mixer which includes the diodes on both sides of the band pass filters of a transceiver but not the transmit receive switching diodes which typically are already high quality PIN types He also adds some notes on Japanese switching diodes which might be used to replace the bad diodes seen in the past Page 56 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 57 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 58 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Pag
127. stronger ones the band may seem noisy or ghost or unreadable signals may appear The advantage of the PINs is that they act theoretically as controlled resistor they can rectify and mix only for the signals at frequency lower than the one corresponding to its carrier lifetime and their switching characteristics regarding the produced IMD are much better than for the normal diodes You may understand now why PINs having large carrier lifetime specification as the BA479 are better for HF than the ones having very small carrier lifetime they may maintain the same good IMD behaviour at lower frequencies and the bigest problem is at the lower bands as Thomas measurements confirm it is just a practical confirmation of the theory Regarding the TX the signals switched during Tx are few they are the mixing products from the Tx mixer and IMD is not a problem as all are originating from the same signal so a PIN will not make large improvement for Tx Actually the Tx IMD are generated by the final amplifier Jeff please note that the proffesional Rx if not using relays for the BPF switching then they are using good PIN diodes So using PINs instead of the existing diodes is a good thing especially if the above mentioned problems seemed to occur so include the presence of the strong signals of the broadcast bands But if big signals are not present if have a good quiet location like yours and when considering the cost and the effort involved it
128. switching diode at 7MHz and the lower bands at a forward current of 17mA There is no relevant difference at 10 MHz and higher It would also be interesting to know how the diodes behave at frequencies below 1 75 MHz Unfortunately my combiner is not appropriate for a lower Page 89 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm QRG But I compared the generation of harmonics by the Kenwood diode and the BA479 at lower frequencies and found the BA479 still to be better than the Kenwood diode even at frequencies down to 100KHz The above measurements also show that the BA479 has a slightly higher insertion loss than the Kenwood diode This is a well known disadvantage of pin diodes also adressed in the excellent articles on your web page In the case of the BA479 however the effect is less than 1dB and therefore probably negligable in the 50 Ohm system of the TS 940 To confirm this I also used a dB meter to determine the insertion loss of two Kenwood diodes in series compared with two BA479 in series At 17 mA diode current two Kenwood diodes produce a loss of 0 2dB at 1 75 and 0 1 dB at 3 5 though 28 MHz Two BA479 in series cause a loss of 0 8 dB at 1 75 and 3 5MHz and 0 7dB at 7 through 28MHz So there is a clear difference but probably without much importance What are the consequences As long as a broadband antenna feeds the TS 940 the front end before the bandpass diodes D3 D5 D
129. t mode while in CW will help lessen noise if that is the main issue The TS 940 is a great radio Have fun I hope this information is helpful Page 115 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm 73 es gd dx John WA2OOB Service Manual amp Serial Numbers Clif Clif lt clif avvid com Fri 12 Jul 2002 14 03 51 0500 Which revision Original Manual Copyright 1985 2 Revised Manual Copyright 1985 2 1985 9 1986 2 Revised Manual Copyright 1985 2 85 9 87 3 87 4 87 10 88 4 88 11 89 08 90 3 That is from 3 different manuals looks like a sackful of revisions are out there Clif Holland KA5IPF Original Message From Brian P Mileshosky lt n5zgt swcp com gt To lt kenwood mailman qth net gt Sent Friday July 12 2002 1 11 PM Subject Kenwood TS 940S Service Manual amp Serial Numbers gt Hello Everyone gt I have a gentleman who has an original Revised Edition Kenwood TS 940S service manual However I do not know what serial numbers it is good for My TS 940S serial number is 6030606 Can anyone please comment on if the revised edition is the correct manual to have given my serial number gt gt Thanks and 73 gt Brian N5ZGT SERVICE MANUALS These can be found from time to time on the internet If you need a service manual we offer it on a comprehensive CD ROM which contains in PDF format a complete set of TS 940 documents 13 Service Bulletins above
130. t a 47 ohm 1 2 watt resistor in series with the collector of Q 6 to limit inrush current on turn on Replace the pass transistor Q101 Q102 with 2N5886 if these short it puts 42 volts on final unit and burns out the expensive driver transistor in about 30 seconds Resolder the complete board amp deflux it too Observations by ZL4AI Original Diode Specifications ZL4AI thinks the file below gives MTZ diode operating values MTZ specs MTZJ_LESHAN pdf Possible Replacement Diode Specifications 1n_Formosa pdf 1n_General pdf 1N_JDG pdf 1N_Leshan pdf 1N_Rectron pdf 1n47__Vishy pdf 1n4728A to 1n4753A Hitachi pdf bzx85C__Fairchild pdf Original Original 1 Original 1 Measured in service at Replacement 1 Replacement 2 Measurements tak replacement D1 D2 D10 to D 13 1N5404 400V 3A 1N5408 1000V 3A D4 500 mW 1N4742 1W 12V BZX85C12 1 3W D8 500 1N4746 BZX85C18 Page 144 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm D9 is difficult to find a replacement match for Kenwood Original is MtZ 9 1 JA which has voltages between 8 29 gt 8 73 median 8 53V Kenwood alternative part is MtZ 8 2 JC which has voltages between 8 03 gt 8 45 median 8 24V Possible replacements 1N4738 8 2 V 0 5V 1N4739 9 1V 0 5V Installed and measured I found 1N4738 output 7 27V at AVR terminal 9 pin 8 ie 0 63
131. t by S point variation on switching If you could prove the point more all hams would be very appreciative of your good work This could be done for both Q10 and Q4 2 different switches These could be mounted on the right side of the top hatch and act as more adjustment controls for the 940 I thought about doing this for R149 and R 150 but decided it was not necessary Now with R149 and 150 swapped I have to turn on 10dB or 20dB attenuation to diminish a strong signal Re solder joints and connectors I already have a section about this on the web page It needs more work and more information on soldering especially You of course are correct about that but it is a separate matter to reversing the FETs There is another possibility I actually fund on my PLL board a missing trace Wow This meant the oscillator never worked on my radio I m sure some other 9404s also have this problem Yours sincerely Jeff King zl4ai Original Message From Eduardo Guisard mailto eduardo guisard com Sent Sunday 12 June 2005 9 28 a m To jaking es co nz Subject TS 940S Some few considerations Page 150 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Hello Jeff PY1NR asked me to also say that he modified 2 two TS 940S from 2 different originations The same improvements of gain and AGC were found He cannot precisely measure the gain improvement due to poor instrumentation He also wants
132. terference on top the signal you want to hear Hence Pin Diodes significantly improve the selectivity of the receiver Traian please confirm this understanding is correct Not quite so The PINs will have big advantage for Rx only Page 96 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm The problem with the normal junction diodes is that when they conduct when the filter is switched in line the far out of band signals may cause 2nd order IMD and the close or in band signals may cause 3rd order IMD Note that the in band mean inside the BPF which may have many MHz bandwidth Actually the diode act like a mixer such simple one diode mixers are used especially at SHF You may see how it hapen if consider the unwanted signals which will be mixed by the diode For example when receiving the 14 MHz band here in EU if big signals exist in the 41m broadcast band they may cause second order IMD a 7110 and 7150 kHz BC stations may produce a ghost signal at 14250 kHz as second order IMD the same will hapen for different bands frequencies Also when receiving the 40 m ham band two signals on the 41m BC band may cause 3rd order IMD apearing as ghost unreadable or carrier signals on the 40m amateur band These are only particular examples as when the propagation is good many hundreds of signals arrive simultaneously at the RX diode bandpass filters input which may cause a lot of trouble especially the
133. that is not true 160 operation 5 I would like to try the IC 775 More money but the automatic carrier null is very fine On CW I would like to try one on 160 for a while myself and see about the noise removal system 6 I understand TenTec has a Omni 6 just out with dsp I have no way of trying it and the TenTec chemistry and my body chemistry do not get along so I will never buy one I do have friends on 160 with Omni 5 and Omni 6 radios doing well They do have good beverages One has a directional vertical array I do have a TenTec tuner I like a lot There is no chemistry problem without electronics inside the box HI George Guerin NE3H compares the 940 to the Omni VI not the VI On the OMNI no question best receiver that I ve ever heard Yes I think the FULL DSP receivers may be more sensitive or have lower noise floor but none of the HAM gear that I am aware of I cannot hear the diff between my old 940 and the OMNI if normal ambient noise most people cannot hear the diff The outstanding characteristic and the second reason I got TWO OMNIs is that you can have an S9 20 signal next door to one in the mud and it does not make a difference I have a neighbor a mile away who runs a kW on RTTY as do I and we can op within a Khz or two without disturbing each other Fact is if you have lots of line noise I don t think you ll
134. the YG 455C 1 in the 455KHz I F You can use either one or both at once to provide a cascade effect in terms of narrowing the response in the upper I F prior to the secondary filter making the rejection of out of passband signals even more pronounced especially helpful if they are strong signals You gain selectivity and rejection of out of passband signals The in band noise should not be affected lessened by having 2 filters in cascade Note there is also a YG 455CN 1 250Hz narrow CW filter available for the TS 940 although this may be at greater expense If noise is the problem the narrower filter will have a better signal to noise ratio by 3dB over the 500Hz filter assuming the same insertion loss I am using the YG 455C 1 by itself with excellent results especially when used in conjunction with the CW VBT control and Notch Filter this helps to notch out noise as well as nearby signals but I am not heavily working CW nor do I have excessive noise If you are heavily into CW and especially CW contesting then using both filters or better yet using the YG 455CN 1 250Hz Narrow CW Filter in the 455KHz I F would likely provide the optimum performance If noise is your main issue it might be worth it for you to start with the narrow YG 455CN 1 CW filter that might be all you ll need If not you can always add a second filter in the 8 83MHz I F BTW use of the RF Attenuator or backing off on the RF gain control and using the AGC in Fas
135. tion Until further research verifies otherwise only replace odd numbered diodes that carry less than 10 MHz Above 10MHz BA479 has more attenuation than the Kenwood 1s2588 so leave the original 1s2588 in place It maybe better to hold off any replacement until research is completed Original Message From Jeff King mailto jaking es co nz Sent Monday 13 June 2005 9 53 p m To thomas hohlfeld Subject RE TS 940S pin diode part 2 and some other considerations Hi Thomas Thanks for this Just to verify I understand you correctly At 17 ma you advise The above measurements also show that the BA479 has a slightly higher insertion loss than the Kenwood diode This is a well known disadvantage of pin diodes also addressed in the excellent articles on your web page In the case of the BA479 however the effect is less than 1dB and therefore probably negligible in the 50 Ohm system of the TS 940 To confirm this I also used a dB meter to determine the insertion loss of two Kenwood diodes in series compared with two BA479 in series At 17 mA diode current two Kenwood diodes produce a loss of 0 2dB at 1 75 and 0 1 dB at 3 5 though 28 MHz Two BA479 in series cause a loss of 0 8 dB at 1 75 and 3 5MHz and 0 7dB at 7 through 28MHz so Jeff King concludes that Two BA479s at 17 ma show Page 93 of 1
136. tm Page 15 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 16 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 17 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 18 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 19 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 20 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 21 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 22 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 23 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 24 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 25 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 26 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Page 27 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm RECEIVER PERFORMANCE IMPROVEMENTS R1 KENWOOD PRODUCED 3 SERVICES BULLETINS which do considerably improve the receiver AGC circuit improvem
137. to emphasize that is very important to fix all contact fails very common in many TS 940S The contact fails could mask the improvements that the modification may occur There s another Brazilian ham that did the mod and found no difference the first time But later on he found a defect on the VR2 trimpot After this correction he got 6 dB more at 1 8 Mhz and 12 dB at 28 Mhz It s also very important to fix all eventual defects before the make the mods described by PY1NR Thanks and regards EG PY1BR Original Message From Eduardo Guisard mailto eduardo guisard com Sent Saturday 11 June 2005 10 51 a m To jaking es co nz Subject TS 940S Hello Jeff I read the comments about the FIELD EFFECT TRANSISTORS AROUND THE WRONG WAY I am PY1BR and together with PY1NR we include all details about this MOD in my website www guisard com The error was found by PY1NR We know that in some cases the differences in the Rx performance or gain may not be important if you correct the FET position on the PCB Please let everybody know through your homepage about all comments we received from many Hams in http www guisard com Index_reviews htm There are many people around the world that agree with improvements after the FET s correction Thanks and regards EG PY1BR Page 151 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm
138. tors are reversed Possibly this is the case for every TS 940 ever made I cannot understand how the circuits would function as the designer intended as the installed resistors are very different to those shown on the schematic diagrams Could you please advise if my observation is correct and after later when Kenwood has investigated if it would be advisable to swap R149 with R 150 and vice versa At this time could you please just confirm that the question will be investigated I look forward to your reply Yours sincerely Jeff King ZL4AI RECEIVER 4 PIN DIODE IMPROVEMENTS This improvement is not fully documented yet Please send in information 4 1 Background on how Pin Diodes were discovered to improve radios TenTec Pin Diodes Paragon Chester Alderman chestert pressroom com Wed 17 Sep 1997 17 14 45 0400 TenTec builds a great amateur radio and obviously to give you a million dollar radio that cost the user five bucks picture PIN diodes have been around for many years however they were initially invented designed manufactur devices obviously because you can not use mechanical relays for internal switching within a microwave RF circui frequency device until within the last 20 years or so Dont quote me on this because I ve been out of microwave design for too long A regular diode is a piece of silicon side of the junction is doped during mfg process to have an excess of electrons P and the other side of the diod therefore t
139. umber 6 02x xxx USA model Serial number 6030687 USA model Serial number 7 xxx xxx USA model Serial number 9 xxx xxx USA model Comment IF BOARD C129 Exists Removed Removed Removed Exists Removed IF BOARD R152 Exists Exists Removed Removed Exists Removed Reason removed unknown Any information would be appreciated IF Exists Removed Removed Page 126 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm KENWOOD RELEASED INFORMATION KENWOOD AMATEUR SERVICE BULLETINS Available at http www kenwood net indexKenwood cfm do SupportFileCategory amp FileCatID 1 ASB0896 jpg TS 940S LCD Clock Display Erratic Operation 81 38 KB ASB0900 JPG TS 940S PLL Unlock 54 42 KB ASB0907A JPG TS 940S Antenna Tuner Relay Damage Modification 69 35 KB ASB0907B JPG TS 940S Antenna Tuner Relay Damage Modification 29 92 KB ASB0908 JPG TS 940S PLL Unlock Due To Low Levels 91 39 KB ASB0909 JPG TS 940S AVR Unit Capacitor Change Failure 104 22 KB ASB0910A JPG TS 940S AGC Circuit Improvements 61 02 KB ASB0910B JPG TS 940S AGC Circuit Improvements 60 39 KB ASB0912A JPG TS 940S Transmitter Hum In SSB 71 53 KB ASB0912B JPG TS 940S Transmitter Hum In SSB 41 30 KB ASB0913 JPG TS 940S Signal To Noise Ratio Improvement With NB 60 94 KB ASB0917A JPG TS 940S VCO Carrier To Noise Ratio Improvements 89 43 KB ASB0917B JPG TS 940S VCO Carrier To Noise Ratio Improvements 59 09 KB ASB0917C JPG TS 940S VCO C
140. utely found a significant increase in received signal levels with no audible increase in noise floor I wondered why other users were not rushing to do the fix and then saw several posts denying the validity of the fix However since I did not effectively document this in a scientific manner I could not effectively offer valid proof of the results When I mentioned this to one of my RACES group leaders who also owns a TS 940 he decided that we would to do the fix to his unit but this time we would document the results using a repeatable local test signal The documented results after each FET was reversed we found a 1 S unit improvement in received signal level using our local test signal in the 20 meter band for a total of 2 S units receive gain improvement Now there is much conjecture regarding the dB value of S units and other TS 940 users may know what these 2 S units on the TS 940 meter mean in terms of dB Generally from my research each S unit may represent 5 or 6 dB of signal which means the fix has increased receive gain 10 to 12 db Certainly nothing to sneeze at being able to give one of the finest receivers made the full scope of RF gain that it was originally intended to have at no cost and without negative repercussions As the bands wane on the downside of the sunspot cycle and running only a vertical 10 feet off the ground I am finding I can use all the noise free gain available to hear DX At any rate this was my
141. very helpful comments and recommendations How hard was it to make the resistor mods you describe on the IF board Also I found an SO 1 for mine how difficult are they to put it Have you done any pin diode modifications Thanks for the great website 73 Mark W0NCL Original Message From Traian Belinas mailto traian belinas deck ro Sent Monday 13 June 2005 5 05 p m To jaking es co nz Cc eduardo guisard com thomas hohlfeld Subject Re TS 940S Some few considerations Hi all Jeff thank you for keeping me informed about the TS940 work and about your website and please continue doing it Please also pass any usefull info to me also I am interrested about Using switches for comparison of the normal reverse FET state may be not feasible even in the case of using shielded cables The added hardware switches and cables will unbalance the mixer in the case of Q4 or may cause other Rx problems in the case of Q10 so the comparison may not be made this way or can be irrelevant A better aproach shall be using hole contact pins for the FETs and reversing them one or another position for comparison Don t let the contact pins there don t forget removing them as the Q10 runs at high drain current and so it runs normally very hot and its cooling is made mostly by the terminals conduction and by the PCB traces path Tnx amp GL Page 149 of 151 KENWOO
142. x out of these two compartments Standing the transceiver on end tipping it toward me and putting a piece of cardboard under the shield can to catch the wax as it drips out Some will run out under the shield but it can be picked off with a Q tip stick or other The alignment was not changed in either circuit but it wouldn t hurt to check the adjustments in those two areas after the meltdown They are simple peaking adjustments Solder troubles are more common in the TS 440 and TS 930 but could be a problem in the 940 as well My AVR board had a LOT of solder problems but I have not reworked VCO areas 73 Garey K4OAH Atlanta PLL BOARD 3 Identify which PLL is not locked From k8aicurt lt k8ai gt Date Tue Nov 30 2004 1 57 pm Subject Re PLL unlock k8aicurt Page 99 of 151 KENWOOD TS 940 PAGE 5 14 2006 http homepages ihug co nz jaking TS 940_02 htm Well I finally got it working There is a line on the PLL board that goes to the control unit that s labeled UL This line goes low if one of the individual PLL IC s is in unlock from both the PLL board and the carrier board If you have dots on the display first disconnect connector 2 on the PLL board and check the voltage at connector 5 pin 5 If the voltage is high 4 6V then the unlock is on the carrier board If the voltage is still low 0V then replace the 2 connector and then check the voltage on the individual IC s Check the voltage on IC8 pin 2 IC9 pin 2
143. ything a higher voltage maybe better hence the higher original values on the circuit diagram Also as rule of thumb voltage regulators should be feed by 2 5 volts higher than their regulated output IC8 on control unit has an output of 17 9 v so lowest feed voltage should not be below 2 5v and that is 20 4 volts ZL4AI believes the best approach is as taken by DF5KF Put in better cooling at each overly hot component Power Supply HEAT SINK RUNS TOO HOT quickfaststang lt scott vitiello verizon net gt wrote I just bought a ts 940 off of ebay Had it on for about 3 hours just receiving and i noticed the unit was getting pretty hot i also noticed the fan or fan s are not working Now i believe they are tempature controlled So my question s are Do these radio s normally get real hot before the fan kicks on Also I am sure this is a common problem So What usually is the cause of this Is it the motor probabally burned out or the thermistor etc Also I believe there are 2 fans one in the tranformer area and one in the final section I dont believe any of them are working but my main concern would be the tranformer fan first ZL4AI measured original DF5KF measured original above on circuit diagram ZL4AI replaced D14 with 1N4748 209 1W D14 marked 22D 1N4748 209 across D14 22 8v 22 7v 24 3v 22 8v pin 3 21B on the Control unit 21 6v pin 5 21T on AVR 21 6v 21 2v 23 2v 20 7v pin 5 21B on AV

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