TL-922 Revival(tm) - Kessler Engineering
Contents
1. ineering LLC Figure 2 35 Electronic Bias Schematic Diagram www KesslerEngineeringLLC com m m a FR nt h er 2 kal m Ter A LIG KJE Figure 2 36 Electronic Bias PCB www Kessler EngineeringLLC com 43 44 Service and Warranty Warranty Kessler Engineering LLC warrants all of our products to be free from defects in material and workmanship under normal use for a period of one year from the date of purchase During this one year warranty period Kessler Engineering will opt to either repair or replace the product This warranty will be void if the product has been repaired or altered by anyone other than the staff at Kessler Engineering This warranty does not apply to products damaged due to improper installation or abuse misuse Repair Policy Please contact our service department for return authorization and shipping instructions prior to sending any product for service or repair All items shipped to Kessler Engineer ing must be packed appropriately and insured against damage Kessler Engineering is not responsible for merchandise damaged in shipment Be sure to include a note describing the problem in detail and include your contact information phone number and e mail Return Policy All returns must receive prior authorization Returned items must also include a copy of the original sales receipt and be returned with the original box manuals and accessories Returns must be re2. seen Far be bak Sw SS EA 2 18 RF Choke to Bandswitch Connection vc podre ak ka bd wow oe 2 19 QSK PCB to QRO Output Connections o o 2 20 Zener Bias Diode Prior to Removal 02000004 www KesslerEngineeringLLC com 2 21 2 22 2 23 2 24 2 25 2 26 2 27 2 28 2 29 2 30 2 31 2 32 2 33 2 34 2 35 2 36 vi Amplifier Chassis After Zener Bias Diode Removal 24 PCB Installation Preparation 3 2 8 642054 RE DR 68244 5a RE EE 25 Electronic Bias PCB Installed 24 2 2 4442 RR AE web eed 26 Amplifier IG connection sa eoc AE 4424 KERE RARR 5 42 ORES g 28 Standby Operate Switch RY connection 00 0 4 29 RI CONT to TX connection os cdas ane Dita E AE ERS 29 Complete Installation of QSK Electronic Bias and Step Start 31 Electronic Bias ZSAC Adjustment Jumper 35 Step Start Schematic Diagram es eg ww ee OR eS RS 38 St p Start POB au saus edna daan K RKR Ee at 39 OSK T R Relay Schematic Diagram suas une be ER Rd N ae 40 QSK T R Relay PCB dps ork ad 604 p din eee Oe ER a bl bid gata E 40 LED Schematic Diagram s sid ec eas e B eee N 41 LED POB OE EE eek eeh dere bk AR DR 41 Electronic Bias Schematic Diagram 42 Elestrome Bias POB sa agere tda iet MEE ib MEG dE T 43 www KesslerEngineeringLLC com List of Tables 2 1 TL 922 Revival Modification Kit Contents ss ss ss sk 0 www KesslerEngineeringLLC c
3. Cut and remove the stock grev coaxial cables near the SO 239 connectors Remove all remnants of the grev coaxial cables and remove the solder from the SO 239 center pins etc e Remove and retain the two metal screws holding the bias relav www KesslerEngineeringLLC com 16 e Remove and discard the bias relay lifting it upward and slightly forward cutting each attached wire as necessarv When finished there should be a small rectangular opening in the chassis located between the RF Input and RF Output SO 239 connectors as shown in Figure 2 12 G Ys Figure 2 12 After Bias Relay Removal The QSK T R Relay PCB has a board mounted male two pin connector This connector mates with a corresponding female two pin connector One wire is yellow and connects directly to the 10 pin Bias PCB connector One wire is brown and needs to be soldered to the High Voltage transformers TH 1 terminal visible in Figure 2 10 e Follow the 22 brown wire shown in Figure 2 12 and de solder it from the High Voltage transformers TH 1 terminal Solder the brown wire emanating from the female two pin connector to the TH 1 connection on the High Voltage transformer NOTE This brown TH 1 wire should be routed near the chassis since this makes the final wire harness lash up much neater e Orient and place the QSK T R Relay PCB over the chassis opening e Fasten securely with two metal screws Solder the
4. 24 a Web d a Sats 2 sva 27 204 IG ens Connection ensen 4844 Did Ge Ad 27 2 8 5 Ele trical Checkouts s scs e wosa e ries RAE 31 2 8 6 Electrical Schematics seance RE ai eo stins kds 38 www KesslerEngineeringLLC com 3 Service and Warrantv Bibliographv A User Notes 4 1 User Notes Continued s soa 200000 00 ee rak 4 2 User Notes Continued 4 3 User Notes Continued www Kessler Engineering LLC com 44 44 List of Figures 21 TL 922 Revival Upgrade Kit Contents Ann or vage kok ERA 22 Stock Lamps Prior to Removal o ss RE WE erosiones 2 3 Panel with Illumination and Status Lamps Removed 24 LED Circuit Board Correctly Installed So Rear Fan Enclosures sas ss pls ores pie aoe A FASE OS 2 6 Mains Voltage Selection Terminal Strip ooo a a 2 7 Inserting Step Start PCB and Routing Wire Leads 2 8 Step Start PCB and Terminal Strip Orientation 2 9 Stock Fuseholder Configuration a vene Kake mee SR EE ee N EN 2 10 Step Start to Fuseholder Connection o 2 11 Bias Relay Prior to Removal a ER RS RE seb BR RR ER ee 2 12 After Bias Relay Removal 2 13 OSK T R Relay POB Installed lt lt lt EE RUG GR ewe ace bees 2 14 Stock T R Relay Prior to Removal 2 saks dies aj Fo 444 welled ea sv 2 15 Amplifier after T R Relay Removal 22444 ss 2 16 QSK PCB to Tuned Input Connections circos en 2 17 QRO Output to Coax Connection
5. 922A variants Although a stock TL 922A will not operate on 10m all of the components necessary for 10m operation were installed in the A variant and 10m operation may be enabled by removing a mechanical stop on the bandswitch and minimal rewiring of the 10m tuned input network www KesslerEngineeringLLC com 2 2 Shortcomings in the Stock TL 922 TL 922 in its stock configuration has a number of impairments that adverselv affect its operation and longevitv Some of these include 1 2 The Parasitic Oscillation Excessive Filament Voltage High Voltage High Current PTT Switching Excessive In Rush Current Loud Hot Switching T R Relay Slow relay controlled tube bias Non QSK Meter lamps that are no longer available most significant problems which require immediate attention are items 1 and 2 the amplifier s tendency to oscillate and its excessive filament voltage Both of these problems are well described and resolved via an upgrade kit already available from AG6K 8 If left uncorrected these problems greatly affect amplifier reliability resulting in premature failure of the 3 500Z vacuum tubes which are increasingly expensive www KesslerEngineeringLLC com 2 3 TL 922 Revival Hardware Upgrade Kit Features Kessler Engineering s TL 922 Revivalcem hardware upgrade kit provides 1 2 5 6 Step Start In Rush Current Protection Low Voltage PTT Switching for use with modern soli
6. switch set to the CW position Idling current also known as Zero Signal Anode Current ZSAC is the anode current that flows when the tubes are biased On without RF drive signal The RF exciter will not be attached to the amplifier for anv of these tests The 3 500Z vacuum tubes mav be operated upright or upside down However the tubes may not be operated when oriented horizontally The tests may only be performed with the amplifier either upright or upside down The stock TL 922 featured a fixed non adjustable cathode bias Zener diode The Electronic Bias PCB includes adjustable bias The bias is adjusted by setting a jumper to l of 7 possible bias settings Moving the bias jumper closer to the front of the amplifier will increase ZSAC while moving the jumper in the opposite direction will decrease ZSAC ZSAC adjustment must NOT be attempted while the amplifier is operating or if plugged into the AC mains 2 fs Y z y Be EG die EEE C E mia aar ua 7 Figure 2 28 Electronic Bias ZSAC Adjustment Jumper 1 Unplug the amplifier from the AC mains 2 Ensure both tubes are installed and that the anode VHF suppressors are properly connected to the tube anodes 3 Install the amplifier top inner and outer covers 4 Place the amplifier upside down www KesslerEngineeringLLC com 5 6 T 8 36 Set the ZSAC control jumper as shown in Figure 2 28 Install the amplifier bottom cover Ensure the amplif
7. voltage selection black termi nal strip e Insert the Step Start PCB between the terminal strip and chassis e Route the wires as shown in Figure 2 7 Route the two 14 yellow wires downward past the right most fuse holder Route the two 14 red wires downward past the left most fuse holder Route the 22 twisted pair and its 2 pin receptacle downward near the SO 239 RF Output connector then toward the front of the amplifier Figure 2 7 Inserting Step Start PCB and Routing Wire Leads e Re install the terminal strip over the top of the Step Start PCB using four two Phillips Head screws Note Occasionallv due to variations in the TL 922 metalwork the mounting hole may be a snug fit If necessary the mounting holes may be very slightly elongated The installed Step Start PCB should appear as shown in Figure 2 8 www KesslerEngineeringLLC com 13 di negri ng LLC j Sep 800700496 2297201 Figure 2 8 Step Start PCB and Terminal Strip Orientation e Reinstall the fan enclosure Figure 2 5 e Remove both AC Mains fuses and set aside e Set the amplifier upside down The stock unmodified AC mains fuse holders are shown in Figure 2 9 Figure 2 9 Stock Fuseholder Configuration e With the amplifier and fuse area oriented as shown in Figure 2 9 de solder and remove the white 14 wire emerging from the upper terminal of the left fuse holder e Solder either one of the 14 red wires emanating from the Ste
8. B www KesslerEngineeringLLC com 29 Figure 2 25 Standby Operate Switch RY connection e Solder the first 8V wire to the 8V terminal labeled 0 4A on filament transformer e Solder the second 8V wire to the SV terminal labeled 8V on filament transformer TX Electrical Connection The TX wire is the amplifier keving control input and must be connected to the amplifier RL CONT jack e Unsolder and remove the stock wire and capacitor from the RCA jack labeled RL CONT e Route the TX wire and solder it to the center pin of the RL CONT RCA jack See Figure 2 26 Figure 2 26 RL CONT to TX connection www KesslerEngineeringLLC com 30 RV Electrical Connection The RY provides electrical current to the QSK T R Relays This wire is already soldered to the QSK T R Relay PCB RY terminal GND Electrical Connection e Solder the GND lead to the filament transformer E ground terminal The filament transformer and Electronic Bias PCB should appear as shown in Figure 2 23 on page 26 www KesslerEngineeringLLC com 31 2 8 5 Electrical Checkout Now that the hardware upgrade steps have been completed inspect the amplifier very closely and remove any remaining debris and wire remnants etc At this point the amplifier should appear as shown in Figure 2 27 NOTE This Figure shows an additional modification to lower the filament voltage a modification to the grid circuitry as well as mod
9. G connection CT Electrical Connection e Solder the CT wire lead to the filament transformer CT terminal 80V Winding Electrical Connections The filament transformer 80V secondarv winding feeds a full wave bridge rectifier DC power supplv used to power the QSK T R relavs The label for the 80V winding mav be partiallv obscured by the transformer warning label However the 80V windings are the two terminals shown on the right side of the transformer just below the E Ground terminal Figure 2 23 e Solder the first 80V wire to the 80V terminal labeled 0 on filament transformer e Solder the second 80V wire to the 80V terminal labeled 80V on filament transformer RY Electrical Connection The RY lead connects to the Standbv Operate switch Refer to Figure 2 25 e Unsolder and remove the wire tvpicallv grev from the forward terminal of the Standbv Operate switch This terminal is shown circled in red in Figure 2 25 e Solder the RY lead to the Standbv Operate switch 8V Winding Electrical Connections The filament transformer 8V secondarv winding feeds a low voltage full wave bridge rectifier DC power supplv used to power the illumination and status LEDs as well as the bias control circuitry As mentioned previously the label for the 8V winding may be partially obscured bv the transformer warning label However the 8V windings are the two terminals shown on the right side of the transformer farthest from the bias PC
10. S Figure 2 19 QSK PCB to QRO Output Connections www KesslerEngineeringLLC com 22 23 2 8 Electronic Bias PCB Installation Svnopsis The amplifier s Zener bias diode and heatsink will be removed The Electronic Bias PCB will be installed and new connections will be made to the filament transformer and the primarv control PCB 2 8 1 Zener Diode and Heatsink Removal The stock Zener diode and its associated heatsink are located adjacent to the filament trans former as shown in Figure 2 20 This area will be used to hold the Electronic Bias PCB Figure 2 20 Zener Bias Diode Prior to Removal Cut the brown wire where it attaches to the Zener diode This is the IG connection described subsequently Remove and retain the screws holding the heatsink to the chassis Remove and retain the screw holding the terminal strip next to the Zener diode e De solder the diode from the ground post e Remove the electrolvtic capacitor and terminal strip located to the right of the filament transformer in Figure 2 20 www KesslerEngineeringLLC com 24 e Remove the ground post near the filament transformer If unable to remove then snap off the ground post as close as possible to the chassis max height e Remove all wires connected to the Filament Transformer s 8V and 80V windings e Do NOT remove either the 14 yellow wire or the 14 red wire shown in the upper portion of Figure 2 20 These two wires supply f
11. TL 922 Revival Kenwood TL 922 Linear Amplifier Hardware Upgrade Kit Installation Manual KENWOOD DP N eae 28 TL 922A i LINEAR AMPLIFIER AW P O Box 341543 Beavercreek Ohio 45434 14 March 2015 Copvright 2012 Thank You At Kessler Engineering we endeavor to make your ham radio hobby more enjoyable and trust that our products will bring you many years of faithful service We Thank You for the confidence that you have placed in us and in our products 79 Dr Donald J Kessler Ph D President Kessler Engineering LLC www KesslerEngineeringLLC com ill Contents 1 Caution 1 Ll You May be Killed 3 oi Fi 284 ELE DEERE AAA A BL ee id 1 2 Introduction 2 2 1 General Description and Purpose o knea 2 22 Shortcomings in the Stock IL 922 ssa s rea EER AG GE NE N 3 2 3 TL 922 Revival Hardware Upgrade Kit Features 4 DAY Preparation is 8 suna bn sd bb b be cere Die oe Jn RE he Oe SE 6 dal To ls Merel s es mesener DE bba BRA 6 20 LED Board Installation us eas deren a B REO TEGN R 8 26 Step Start PCB Installation ee lt lt 440464 pd skate desk gt 11 27 OSK T R Relay POB Installation lt lt ses rea Sa 15 2 7 1 Stock T R Relay Removal 18 28 Electronic Bias PCB Installation seas ameda 28 2 8 1 Zener Diode and Heatsink Removal oaaao 23 2 8 2 Electronic Bias PCB Installation 2 ans aa amiden ka 25 2 8 3 Electronic Bias PCB Connections 224
12. amps etc may be ignored since these components are removed and discarded during the modification process However other problems such as defective tubes bad high voltage power supply etc will not be cured by merely installing this modification kit and should be resolved first The TL 922 Instruction Manual 1 and the TL 922 Service Manual 2 are excellent ref erence documents and one should consult them and become very familiar with the electrical as well as mechanical layout of the amplifier prior to performing any work on the amplifier Copies of these manuals are available from various sources on the Internet quite often as a cost free download The hardware upgrade kit entails installation of four printed circuit boards PCB mak ing connections to those circuit boards and soldering to various components within the amplifier Before these PCBs can be installed the amplifier must be partially disassem bled not that daunting and a number of components and assemblies removed from the amplifier The four circuit boards to be installed are e LED Front Panel Display and Meter Illumination e QSK T R Relays e Step Start AC Mains Current Limiting e Electronic Bias Control of tube Bias Step Start QSK LED and Soft Switching 2 4 1 Tools Required e 2 Phillips Head Screwdriver e 2 Right Angle Drive Phillips Head Screwdriver Wire Cutters Wire Strippers Small Needle Nose Pliers Small Vise Grip Plier
13. ceived within 7 days of purchase and are subject to a restocking fee Shipping expenses are not refundable www KesslerEngineeringLLC com 45 Bibliographv 1 Kenwood Corporation Linear Amplifier Model TL 922A Instruction Manual B50 2587 00 G 2 Kenwood Corporation Service Manual TL 922 Linear Amplifier B51 0835 00 April 1994 3 Richard L Measures Improving the Heathkit SB 220 Amplifier QST pp 42 Febru arv 1989 4 Richard L Measures Improving Amplifier Parasitic Suppression for Modern Amplifier Tubes QST pp 36 38 66 89 October 1988 5 Richard L Measures Circuit Improvements for the Heath SB 220 Amplifier Part 1 QST pp 25 29 November 1990 6 Richard L Measures Circuit Improvements for the Heath SB 220 Amplifier Part 27 QST pp 41 43 December 1990 7 Richard L Measures QSK for the TL 922 and SB 220 With Circuit Improvements for the TL 922 http www somis org QSK922 html October 2004 8 Richard L Measures http www somis org 9 Richard L Measures The Nearly Perfect Amplifier QST pp 30 34 January 1994 www KesslerEngineeringLLC com User Notes www KesslerEngineeringLLC com 46 4 1 User Notes Continued www KesslerEngineeringLLC com 47 4 2 User Notes Continued www KesslerEngineeringLLC com 48 4 3 User Notes Continued www KesslerEngineeringLLC com 49
14. com AT 4 Set the LINEAR switch to STBY Confirm illumination of the STBX light 5 Electrically short the Open end of the keying line cable Confirm ON AIR light illuminated STBY light extinguished Observe and note anode idling current IP for proper ZSAC level 6 Open the keving line Confirm that anode current returns to 0 7 Switch the amplifier OFF If necessary the idling current should be adjusted to achieve approximately 180mA MODE switch to SSB To do so unplug the amplifier from the AC mains Wait approximately 30 minutes for the HV to bleed off then move the bias jumper in the appropriate direction to increase decrease idling current Secure the bottom cover and repeat the previous test until proper idling current is achieved Congratulations a you ve gotten to this point passing all of the tests then you ve successfully upgraded your TL 922 with QSK Step Start Electronic Bias etc and it should provide reliable service for years to come Congratulations on a job well done www KesslerEngineeringLLC com 2 8 6 Electrical Schematics 38 1 2 4 FUSBA FUSEB El K2 2 emit ks R g 4 4 H im 2 Mm 2 10 MN 10w 5 s Tj Relay Relay T SWITCH A na SWITCH B ii Step Start Title Prjec Contract ATA TL92 Siep Start L922 Revival PCE Part Number Date Sbeet Revision ssler BOOTOOSA 4 28 2012 4 of4 1
15. d state transceivers Quiet T R Switching QSK Operation Electronic Bias Control LED On Air Standby and Meter Illumination The upgrade kit utilizes four high qualitv removable circuit boards with complete documen tation to facilitate installation service and maintenance of the modified TL 922 amplifier The kit comes with all circuit boards assembled and tested Should a fault develop on anv of these circuit boards it mav be removed and serviced If necessarv thev mav also be returned to Kessler Engineering for repair The complete modification kit comes with the items listed in Table 2 1 and shown in Figure 2 1 Table 2 1 TL 922 Revival Modification Kit Contents Quantity Description 1 LED Circuit Board Step Start Circuit Board QSK T R Relay Circuit Board Electronic Bias Circuit Board Wiring Harness Heat Shrink Tubing Plastic Wire Ties 8mm Hex Nuts Flat Steel Washers Flat Nylon Washers Rubber Grommet LED Diffuser Paper KOMMA HD ND ND www KesslerEngineeringLLC com Figure 2 1 TL 922 Revival ym Upgrade Kit Contents www KesslerEngineeringLLC com 2 4 Preparation We highly suggest performing these modifications on a fully functional amplifier If the am plifier is non functional we suggest repairing the damage if appropriate before commencing the modifications Problems due to a defective T R relay shorted Zener bias diode defec tive bias relay inoperative meter l
16. ears a number of excellent articles have been written such as those published by AG6K 3 7 that highlighted many of these problems and provided very good solutions By applying these solutions the amplifier s shortcomings may be eliminated and its overall operation and longevity greatly enhanced In short a properly modified TL 922 is a very reliable amplifier that will provide many years of flawless service A problem not always easily overcome by those seeking to perform these upgrades is ex actly how and where to implement them as well as where to find appropriate sources of parts Another complication arises when one attempts to service a modified amplifier particularly if modified by someone else Depending upon the modifier s competency willingness to doc ument and overall neatness troubleshooting such an amplifier can become a daunting task Kessler Engineering LLC has overcome these challenges for you by making the process of upgrading the TL 922 amplifier much more practical affordable and serviceable Throughout this document TL 922 will be used interchangeably to refer to both the TL 922 and the TL 922A linear amplifiers The TL 922 and TL 922A are almost identical and these upgrades apply equally to both amplifiers The TL 922 was sold throughout the World as a 160m 10m linear amplifier However 10m operation was disabled at the factory in order to permit importation into the United States hence the TL 922 and TL
17. exposed leads from the QSK T R Relay PCB to the RF Input and RF Output SO 239 connectors www KesslerEngineeringLLC com 17 e Solder the coaxial cable shield to the ground post near the RF Output SO 239 connector When finished the installed QSK T R Relav PCB should look as shown in Figure 2 13 BT ITOOCUVS but aaauTDUR a And 3 us 1 7 ale Figure 2 13 QSK T R Relay PCB Installed www KesslerEngineeringLLC com 18 2 7 1 Stock T R Relay Removal The stock T R relav is adjacent to the tuned input section as shown in Figure 2 14 and held in place bv two screws accessible from the top side of the amplifier through the RF Deck The RF choke shown in Figure 2 14 will be re used Figure 2 14 Stock T R Relav Prior to Removal Carefullv unsolder and remove the RF choke it will be reinstalled later e Remove the two screws holding the T R relay Cut any wires where they connect to the relay and discard the stock T R relay e Remove any remnants of the original grey coaxial cables e Clean all excess solder and residue from the ground posts and post feeding the tuned input e Remove the right side panel to complete this process www KesslerEngineeringLLC com 19 At this point the amplifier should appear as shown in Figure 2 15 Figure 2 15 Amplifier after T R Relay Removal Two coaxial cables emanate from the QSK T R Relay PCB The shorter coaxial cable provides RF drive t
18. g the relavs to close no longer restricting input current When this occurs the meter illumination will increase in brightness and the user should hear the relavs close All of this should occur within the first 2 3 seconds of operation If the Step Start Relavs do not close within this interval it indicates a problem that must be solved before proceeding Whenever the amplifier outer top cover is removed the High Voltage transformer and the cooling fan are unpowered If tubes are installed in the amplifier during these tests the user should limit On Time since cooling airflow will not be present Read through the following steps before actually performing them If any problems are noted switch the amplifier OFF then unplug from the AC mains 1 Ensure the amplifier POWER switch is in the OFF position 2 Plug the amplifier into the AC mains 3 While observing the front of the amplifier switch the amplifier ON www KesslerEngineeringLLC com 33 A Confirm both meters are illuminated 5 Confirm operation of the Step Start Relav Within l 2 seconds after switching the amplifier ON the Step Start Relav should produce a soft Click and the meter illu mination should noticeably brighten 6 After approximately 20 Seconds switch the amplifier POWER switch OFF If the amplifier Step Start Relav energized properlv and the meters illuminated then bright ened after the Step Start interval proceed with the following tes
19. i i Engineer Dawn By Revision Date ngineering Don Kessler DIE 4 20 2012 Hi Project Kessler EE LLC P O Box 341543 TL922 Step Start FjPeb Loca tion XiCurent PmjectTL92ATL922 step start SchDoc Beavercreek Ohio 45430 458 1174 1 2 3 4 Figure 2 29 Step Start Schematic Diagram www KesslerEngineeringLLC com Kessler Engineering LLC TL 922 Step Start BOO 004A 4 29 2012 install PCB behind terminal block Figure 2 30 Step Start PCB www KesslerEngineeringLLC com 39 40 w w 1 18 RFOUTPUT RFDECK A 18 1 4 RG 8X Center Conductor Length TUNED INPUT 15 12 RG 3X Pou Bar 341543 EE Ohio 45430 2 ngineering LLC D ineering LLC it Dat F Location Z Cument Project VILS2ATL92 zelay SchDoe a w Figure 2 31 QSK T R Relay Schematic Diagram Figure 2 32 QSK T R Relay PCB www KesslerEngineeringLLC com 41 GID GID METER ILLUMINATION i Engineering LLC is Kessler eering LLC PO Box 341543 Beavercreek Ohio 45430 937 458 Kessler Engineering LLC TL S22 LED BOO7003A Figure 2 34 LED PCB www KesslerEngineeringLLC com 42 MIDMEITG HV XFMR Internal Switch Stock 54 Stand by Operate Switch Mounted to Front Panel ZSAC ADJUST 571 6404562 Dv B Zuma aep arnas Spe 3 3 ONAIR LED PO Box 341543 Beavercreek Ohio 45430 571 6404565 PS
20. ier is switched OFF Plug the amplifier into the AC mains The first portion of this test will re confirm operation of the Step Start and expected High Voltage operation When switched ON the High Voltage will begin to ramp up then plateau until the Step Start Relav is energized At that moment the High Voltage should reach normal levels approximatelv 2kV when MODE switch is set to CW and approxi matelv 3kV with MODE switch set to SSB 1 2 8 Set the MODE switch to CW Set the METER switch to HV Set the LINEAR switch to STBY While observing the HV meter switch the amplifier ON Confirm Step Start Operation Confirm HV ramps up initiallv plateau then reaches approximatelv 2kV after Step Start Relav activation Confirm that there is no anode current IP reads 0 Switch the amplifier OFF Set the MODE switch to SSB While observing the HV meter switch the amplifier ON Confirm HV ramps up initiallv plateau then reaches approximatelv 3kV after Step Start Relav activation Confirm that there is no anode current IP reads 0 Switch the amplifier OFF The operation of the Electronic Bias will be confirmed iP 2 3 Insert the amplifier keying line into the RL CONT jack Ensure the free end of the keying line is electrically Open While observing the HV meter switch the amplifier ON www KesslerEngineeringLLC
21. ification to the cathode drive not included in this modification kit Figure 2 27 Complete Installation of QSK Electronic Bias and Step Start www KesslerEngineeringLLC com 32 Svnopsis Checkout of the modified amplifier will be performed in a series of stages For each of these steps AC mains electrical power will be applied to the amplifier However It is IMPERATIVE that all safetv precautions be observed due to the presence of lethal voltagesl DO NOT TOUCH ANVTHING within the amplifier while it is plugged into the AC mains or whenever High Voltage is present such as from the anode High Voltage power supply 1 Ensure the top outer cover is removed from the amplifier this should ensure the HV transformer will not be energized 2 Place the amplifier upside down on the workbench 3 Install the AC mains fuses 4 Place the amplifier POWER switch to the OFF position 5 Set the amplifier METER switch to the HV position 6 Set the amplifier LINEAR switch to the STBY position Step Start and LED Checkout This test will confirm correct operation of the Step Start circuit as well as the proper se quencing of the ON AIR and STBY lights Whenever the amplifier is switched On the AC mains current flow is limited briefly by the two power resistors on the Step Start PCB After a brief interval approximately 2 seconds the Electronic Bias PCB circuitrv will energize the Step Start Relavs causin
22. ilament current to the tubes and must not be removed unless performing the filament voltage modification not part of the TL 922 Revival kit However Figure 2 21 does show how the filament supply leads might appear if they were replaced during the filament voltage modification e Add a 0 01uF capacitor between the filament transformer C T Center Tap and E Ground terminals Ensure that the stock green wire remains soldered to the transformer C T The filament transformer and area immediately adjacent should now appear as shown in Figure 2 21 Figure 2 21 Amplifier Chassis After Zener Bias Diode Removal www KesslerEngineeringLLC com 25 2 8 2 Electronic Bias PCB Installation The Electronic Bias PCB will be installed in the area formerlv occupied bv the Zener diode and heatsink and will mount directiv to the filament transformer Refer to Figure 2 22 Figure 2 22 PCB Installation Preparation Place a flat washer on each of the two threaded posts nearest to the filament trans former Place the rubber grommet as shown it will be compressed and held in place bv the Electronic Bias PCB Orient the Electronic Bias PCB and lower onto the filament transformer mounting bolts e Place a flat washer and 8 metric nut on the two mounting bolts and tighten Plug in the LED PCB Step Start PCB and the QSK Relay PCB attached to 10 pin connector When finished the amplifier should appear as shown in Fig
23. ity tester 1 Connect one lead of the continuity tester to the center pin of the SO 239 RF INPUT jack Connect the other lead of the continuity tester to the center pin of the SO 239 RF OUTPUT jack Confirm DC continuity between the center pins of the RF INPUT and RF OUTPUT connectors Set the LINEAR switch to OPERATE Open the keying line Switch the amplifier ON Confirm DC continuity between the center pins of the RF INPUT and RF OUTPUT connectors Electricallv short the Open end of the keving line cable Confirm loss of DC continuitv between the center pins of the RF INPUT and RF OUTPUT connectors Measure DC resistance between center pin and ground of the SO 239 RF INPUT jack while the ON AIR light is illuminated Confirm DC resistance less than approximately 200 8 152 typical www KesslerEngineeringLLC com 35 Electronic Bias Adjustment and Checkout This test confirms correct operation of the High Voltage Power Supply and Electronic Bias LETHAL voltages will be present within the amplifier during these tests ALL AMPLIFIER COVERS MUST BE IN PLACE DURING TEST Under normal conditions with a healthy set of 3 500Z tubes the idling current should be approximatelv 180 200mA when operating with the MODE switch in the SSB position whereas the idling current should be approximatelv 90 100mA when operating with the amplifier MODE
24. l Remove and discard the meter lamps bv sliding them upward Remove and discard the Standby and On Air lamps sliding them sideways as necessarv Remove but retain the two screws holding the terminal strip Note We suggest using a right angle drive screwdriver e Cut as necessarv anv wire connected to the terminal strip e Remove and discard the terminal strip and lamps When finished the lamp area should appear as shown in Figure 2 3 e Orient the LED PCB aligning the PCB mounting holes over the mounting brackets used to hold the terminal strip e Place plastic insulating washers behind the PCB attachment holes and then Attach the LED PCB using the two screws removed previously www KesslerEngineeringLLC com Figure 2 3 Panel with Illumination and Status Lamps Removed e Check the orientation of the four illumination LEDs D3 D4 D5 D6 They should point downward toward the meters Orient as necessarv e Refer to Figure 2 3 There is an opening in the metalwork immediatelv above the On Air lamp which provides access to the area directly over the top of the meters Cut an 1 25in by 5in strip of the white diffuser paper and insert the paper strip into this opening between the meter illumination LEDs and the meters Inserting this Diffuser will provide uniform illumination of the meters and prevent bright spots e Check the orientation of the On Air and Standby LEDs They should poi
25. nt toward their respective On Air and Standby plastic filters Adjust as necessary e Route the wire bundle and electrical connector downward next to the bulkhead so that the connector emerges behind the Stbv Operate mode switch NOTE Later versions of the LED Circuit Board do not have wires soldered di rectiv to the circuit board Instead thev have a 5 Pin connector for easier installation and removal In this case connect either end of the cable provided into connector P1 and route the wiring as shown in the Figure When finished the installed LED board should look as shown in Figure 2 4 www KesslerEngineeringLLC com Kessler Ene gi ering LLC 2 J MPL 11 922 LED BOO7003A 571272012 Figure 2 4 LED Circuit Board Correctly Installed www KesslerEngineeringLLC com 10 11 2 6 Step Start PCB Installation Svnopsis The rear fan enclosure will be temporarilv removed for installation of the Step Start PCB The fuse holders will be re wired to place the Step Start circuit in series with the AC Mains fuses and the front panel On Off switch Installation e Remove the four screws holding the fan enclosure Figure 2 5 e Remove the enclosure exposing the mains adjustment terminal strip Figure 2 6 e Be careful not to strain the cooling fan wires Figure 2 6 Mains Voltage Selection Terminal Strip www KesslerEngineeringLLC com 12 e Remove the two Phillips Head screws holding AC Mains
26. o the amplifier and must be connected to the amplifier s tuned input network Refer to Figure 2 16 on page 20 e Solder the shorter coaxial cable s braid to the ground post near the tuned input con nector e Attach the coaxial cable center conductor to the tuned input post Do NOT melt the nvlon insulation The completed tuned input connections should appear as shown in Figure 2 16 www KesslerEngineeringLLC com 20 Figure 2 16 QSK PCB to Tuned Input Connections The remaining coaxial cable provides the RF output signal path from the amplifier s load network to the QSK T R Relay PCB e Solder the longer coaxial cable s shield to the ground post on the side of the amplifier near the output band switch e Solder the coaxial center conductor to the RF output Near the bottom of the load capacitor as shown in Figure 2 17 e Solder one end of the RF Choke to the ground post on the side of the amplifier near the output band switch This is the same post that the coaxial cable shield is soldered to e Solder the free end of the RF choke to the common contact of the output bandswitch as shown in Figure 2 18 The common connection will alreadv have a bus wire running from the RF tank coil and will also 47pF capacitor shunt to ground When finished the amplifier should appear as shown in Figure 2 19 www KesslerEngineeringLLC com Figure 2 18 RF Choke to Bandswitch Connection www Kessler EngineeringLLC com 21 M
27. om vil Caution 1 1 You May Be Killed The Kenwood TL 922 Linear Amplifier contains LETHAL high voltages One must be absolutely careful and fully understand the consequences of working on this am plifier IF you come into contact with any of these High Voltages YOU MAY BE KILLED PLEASE We graciously request that you return the hardware upgrade kit to Kessler Engineering for a full refund including postage if any of the following apply e You are not comfortable working on this amplifier e You are not qualified to perform this work You do not fully understand the potential hazards You no longer wish to perform these upgrades e You are unable to solder You lack proper tools etc e You ve changed your mind etc If for any reason you wish to return this upgrade kit please do so We will refund your purchase and shipping costs ABSOLUTELY NO QUESTIONS ASKED This is a hobby it isn t worth losing one s life over www KesslerEngineeringLLC com Introduction 2 1 General Description and Purpose The Kenwood TL 922 TL 922A is a relativelv low cost HF linear amplifier with outstanding ergonomics These amplifiers were constructed with high qualitv components in a form factor that is attractive functional and unobtrusive Unfortunatelv that original design now 30 years old included a number of design shortcomings some of which were detrimental to the amplifier s operation and longevitv Over the v
28. p Start PCB to the upper terminal of the left fuse holder www KesslerEngineeringLLC com 14 e Solder together the free end of 14 white wire to the other 14 red wire and insulate with Heat Shrink tubing e De solder and remove the white 14 wire emerging from the upper terminal of the right fuse holder e Solder either one of the 14 yellow wires emanating from the Step Start PCB to the upper terminal of the right fuse holder e Solder together the free end of 14 white wire to the other yellow wire Insulate with Heat Shrink tubing e Route the 22 twisted wire pair and connector from the Step Start PCB up and into the amplifier toward the filament transformer When finished with this step the results should appear as shown in Figure 2 10 Figure 2 10 Step Start to Fuseholder Connection www KesslerEngineeringLLC com 15 2 7 QSK T R Relav PCB Installation Svnopsis The stock amplifier s bias relav T R relav and coaxial cables will be removed and discarded The QSK T R Relay PCB with vacuum relay will then be installed completing the quiet QSK upgrade Bias Relav Removal The bias relay is located between the RF Input and RF Output SO 239 connectors as shown in Figure 2 11 Figure 2 11 Bias Relav Prior to Removal Cut the plastic wire ties or string ties in older TL 922 amplifiers holding the grev coaxial cables to the wiring harness Do NOT remove the cathode drive black coaxial cable
29. s www KesslerEngineeringLLC com e Smm Socket e 5mm Hex Key Allen Wrench Soldering Iron and Solder Solder Wick or Solder Sucker e Volt Ohm Meter Heat Gun CAUTIONI Modification of the TL 922 amplifier requires desoldering and soldering of numerous components and connections anv of which are prone to damage if subjected to excessive heat or phvsical force Please use caution WARNINGI ALL electrical power must be removed from the amplifier No Exceptions Under no circumstances should the amplifier be plugged into electrical power switched On etc while performing anv of these modifica tions e Unplug the amplifier from the AC mains supply e Disconnect all other electrical connections to the amplifier e Wait at least 30 minutes after removing AC Mains power before removing any covers from the amplifier e Remove the amplifier outer and inner top covers e visually inspect but do not touch the high voltage safety switch shorting strap and ensure that it is properly engaged www KesslerEngineeringLLC com 2 5 LED Board Installation Svnopsis The amplifier s incandescent lamps will be removed and replaced with a PCB containing six LEDs which provide meter illumination as well as Standbv and On Air status indica tions Installation The stock lamps are held in place bv rubber grommets and electricallv connected to a ter minal strip as shown in Figure 2 2 Figure 2 2 Stock Lamps Prior to Remova
30. t Otherwise unplug the amplifier from the AC mains and begin troubleshooting 1 Insert the amplifier keving line into the RL CONT jack 2 Ensure the free end of the keving line is electricallv Open 3 Switch the amplifier ON and reconfirm proper Step Start operation A Confirm that neither ON AIR nor STBY lights is illuminated 5 Change the amplifier LINEAR switch from STBY to OPERATE Confirm the STBY light is now illuminated 6 Electricallv short the Open end of the keving line Confirm the STBX light is extinguished and ON AIR light is illuminated 7 Set the LINEAR switch to STBV Confirm STBY and ON AIR lights are extinguished 8 Set the LINEAR switch to OPERATE and short the keying line Confirm the STBX light is extinguished and ON AIR light is illuminated 9 Open the keving line Confirm ON AIR light extinguished and STBY light illuminated 10 Electricallv short the Open end of the keving line again Reconfirm the STBX light is extinguished and ON AIR light is illuminated 11 With the keying line still shorted set the LINEAR switch to STBY Confirm STBY and ON AIR lights are extinguished 12 Leave the LINEAR switch set to STBV 13 Switch the amplifier OFF www KesslerEngineeringLLC com 34 If the lamp sequencing works correctly then proceed with the next test to confirm switching operation of the QSK T R Relay For this test we recommend using an audible continu
31. ure 2 23 The connections to the 10 pin plug will be described next www KesslerEngineeringLLC com a de A ED ET SA ED an 810 410 910 sia Pam 10 Ho Ay DYE7 i 20 sy Figure 2 23 Electronic Bias POB Installed www KesslerEngineeringLLC com 26 27 2 8 3 Electronic Bias PCB Connections See Figure 2 23 The 10 pin connector provides the following from left to right IG The grid bias control connection CT Filament transformer center tap 80V Filament transformer 80V output winding 80V Filament transformer 80V output winding RY Standby Operate switch contact Figure 2 25 8V Filament transformer 8V output winding 8V Filament transformer 8V output winding TX PTT control RCA jack labeled RL CONT RY QSK Relay PCB already connected GND Chassis ground connection 2 8 4 IG Electrical Connection The brown IG wire will be used to pull the Electronic Bias IG wire into position Locate and follow the Brown wire disconnected from the Zener bias diode Temporarily solder the 10 pin connector s IG green lead to the Brown wire Disconnect the Brown wire from the amplifier s control board IG post Figure 2 24 Using the Brown wire pull the Electronic Bias green IG lead into position Solder Electronic Bias green IG lead to the control board IG post www KesslerEngineeringLLC com 28 Figure 2 24 Amplifier I
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