"service manual"
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1. Mod corrects open DC force path caused by incorrect wiring 5982 New metal clips improve contact repeatability 5919 New flat head mounting screws improve test fixture mounting 5920 New miniature banana plug cable wire eliminates breakage 5709 170MB hard disk drive update for 16500B mainframe 5993 Country specific firmware is available 5222 Mod remove PS3 to prevent network crashes 5934 Mod improves time stability of DC current ranges 10mA 100 mA 6001 Explanation of indicated calibration failure of AC current 6002 Repositioning int gnding lock washer elimis source sig probs 5999 CR1 on ps brd fails due to excessive tightening of heat sink 6000 Shield reduces magnetic emissions when fan assy replaced 5980 Mod for use with 35659A Opt AMV or HO1 5987 Mod improves reliability of microdot connector 5981 Mod corrects C1405A B Keyboard failures 5922 Instructions to retrofit Opt 001 to a standard instrument 5696 Installation of HP 15850A Opt H03 5697 Mod corrects incorrectly loaded capacitor on transmitter brd 5698 Installing Option 001 into an HP 53310A 5976 New resistor values for ac line input prevents failure 5957 New reset programmable array logic PAL integrated circuit 5983 New PAL circuit allows MODRST line on A4 to be bi directional 5992 New 20 dB attenuator has longer semi rigid cable 5707 RPP Module modification reduces noise floor of RF output 5732 Jitter is normal for internal modulation source 5733 Cable replacement and identification 5775 J2. 8665A 04 IO 8665A 05 IO 8665B 02 IO 8665B 03 IO 8683A 03 IO 8683B 04 IO 8683D 04 IO 8684A 05 IO 8684B 07 IO 8684D 05 MR 8711A 02 MR 8711A 03 MR 8751A 17 MR 8751A 22 IO 8751A 24 IO 8920A 07 MR 8920A 08 MR 8920D 01 MR 8920DTS 01 MR 8921A 01 MR 8921D 01 IO 8990A 01 IO 8991A 01 IO 8991A 02 IO 8992A 01 MA E1222M 09 MR E1300A 02 MR E1301A 03 SA E1401A 02 S MR E1446A 01 MR E1672A 01 BENCH BRIEFS Abstract HP FIRST Document ID No Additional equipment required during Option 012 calibration 5763 List of specific test equipment reqd for Opt 151 163 calib 5988 Additional equipment required during Option 012 calibration 5764 List of specific test equipment reqd for Opt 151 163 calib 5989 Additional equipment required during Option 012 calibration 5765 List of specific test equipment reqd for Opt 151 163 calib 5990 Additional equipment required during Option 012 calibration 5766 List of specific test equipment reqd for Opt 151 163 calib 5991 RPP Module modification reduces noise floor of RF output 5721 Jitter is normal for internal modulation source 5722 Cable replacement and identification 5767 RPP Module modification reduces noise floor of RF output 5723 Jitter is normal for internal modulation source 5724 Cable replacement and identification 5768 RPP Module modification reduces noise floor of RF output 5725 Jitter is normal for internal modulation source 5726 Cable replacement and identification 5769 RPP Module modification
3. reduces noise floor of RF output 5727 Jitter is normal for internal modulation source 5728 Cable replacement and identification 5770 Jitter is normal for internal modulation source 5729 Recommended replacement Reverse Power Protection assembly 5747 Cable replacement and identification 5771 Jitter is normal for internal modulation source 5730 Recommended replacement Reverse Power Protection assembly 5748 Cable replacement and identification 5772 Jitter is normal for internal modulation source 5731 Cable replacement and identification 5773 Field support kit and assembly obsolescence 5700 Field support kit and assembly obsolescence 5701 Field support kit and assembly obsolescence 5702 Field support kit and assembly obsolescence 5703 Field support kit and assembly obsolescence 5704 Field support kit and assembly obsolescence 5705 Cable replacement corrects display instability problem 5717 Incorrect part in service kit incorrect procedure in manual 5718 Modification fixes unexpected spurious problem 5736 Mod prevents hang ups or unexpected resets 5737 New key cap for power line switch 5918 Instructions for replacing the motherboard 5699 Incorrect RF diagnostics results Option 007 5774 Early units require FW upgrade for use with HP 11807A Opt 009 5958 Early instuments require hardware and firmware upgrades 5959 H W and F W upgrade required for 83201A compatibility 5749 Early units require FW upgrade for use with HP 11807A Opt 009 5960 Save A1 control
4. to 25 dBc 5979 4 BENCH BRIEFS WWW HPARCHIVE COM 1ST QUARTER 1994 2 eysa GS SN SN Type No MR IO IO MA MA MR MR MR IO MR MR MR IO MA MR MR MR IO IO IO IO MR MR IO IO IO IO 10 IO MR IO MA MR MA MR MR IO MR MA MR MR MA IO MR IO MA MR MA MR IO MA MA MA MA IO 3589A 03 3784A 03 3784A 04 3784A 05 3785A 25 4155A 01 4156A 01 4291A 01 4396A 08 4396A 09 4396A 10 4396A 11 4396A 12 4957A 01C 4980A 11 4981A 11 4982A 11 S5071A 01 5071A 02 5529A 01A 5529V 01A 6060B 02 6063B 02 6651A 03 6652A 03 6653A 03 6654A 03 6655A 03 8130A 03 8560A 26C 8560A 27 8560A 28 8560E 02C 8560E 06 8560E 07 8561B 25C 8561B 27 8561E 01C 8561E 05 8561E 06 8562A 67C 8562A 68 8562A 69 8563A 20C 8563A 21 8563A 22 8563E 02C 8563E 07 8563E 08 8566B 10B 8566B 19A 8567A 03A 8568A 37B 8568B 08A 8568B 10B 1ST QUARTER 1994 Abstract HP FIRST Document ID No C1405A B keyboard incompatibility with HP 3589A 5937 Mod optimizes the HP 3784A for burst mode operation 5692 Instructions to retrofit Opt 002 to a standard instrument 5693 Mod to housing for pwr supply caps C1 and C2 5694 Mod ensures conformance to performance test 5695 Updating the preliminary ROMs with formal released ROMs 5994 Updating the preliminary ROMs with formal released ROMs 5995 New A3A3 assembly improves osc level self test 15 5968 New key cap for power line switch 5917 New A3A3 assembly improves RF outpu
5. 0 WA cacan I BRikiS SERVICE INFORMATION FROM HEWLETT PACKARD 1st Quarter 1994 The Optical Spectrum Analyzer Part 3 Sensitivity Mike Levernier Hewlett Packard Introduction In the previous issue of Bench Briefs Richard Ogg explained the optical spectrum analyzer in terms of signal processing various operating modes noise generation and the control of noise through filtering schemes In this issue Mike Levernier describes OSA sensitivity through Hewlett Packard s patented way of allowing the user to directly enter the required sensitivity level what HP calls a sensitivity function For more de tailed information on optical spec trum analysis basics order Applica tion Note 1550 4 Optical Spectrum Analysis HP Pub No 5091 3054E from your local HP sales service office tical spectrum analyzers see the pre vious issue of Bench Briefs Figure 1 shows the display of a signal that has an amplitude equal to the sensitivity setting of the optical spectrum analyzer Single monochromators typically have sensitivity about 10 to 15 dB bet ter than that of double monochroma tors due to the additional loss of the second diffraction grating in double monochromators The double pass monochromator has the same high sensitivity of single monochromators even though the light strikes the dif fraction grating twice The high sen sitivity is made possible by the half wave plate and the use of a sma
6. 0322A 03 70700A 01C 70820A 02 1ST QUARTER 1994 Abstract HP FIRST Document ID No Changes to performance test software for pulse on off tests 5752 New table provides correct ref designators during test 3xx 5753 Changes to performance test software for pulse on off tests 5754 Mod corrects synchronization problems in parallel operation 5935 New firmware improves performance 5984 Mod improves reset and fixes crosstalk on F660 control board 5986 Elimination of RF oscillation for lightly loaded supply 5998 New fuse eliminates intermittent blowing Opt 0E3 5971 New fuse eliminates intermittent blowing Opt 0E3 5972 New fuse eliminates intermittent blowing Opt 0E3 5973 New fuse eliminates intermittent blowing Opt 0E3 5974 Inadequate ground may cause possible shock hazard 5961 Fan speed regulator no longer required 5912 Inadequate ground may cause possible shock hazard 5962 Fan speed regulator no longer required 5913 Inadequate ground may cause possible shock hazard 5963 Fan speed regulator no longer required 5914 Inadequate ground may cause possible shock hazard 5964 Fan speed regulator no longer required 5915 Inadequate ground may cause possible shock hazard 5965 Fan speed regulator no longer required 5916 Inadequate ground may cause possible shock hazard 5966 Inadequate ground may cause possible shock hazard 5967 LED board mod allows greater range of brightness adjustment 5932 LED board mod allows greater range of brightness adjustment 5933
7. 8 Hz S the SPAN 5 008 nm ST 388 msec o RL 0 34 dBm RSENS 33 dBm 5 00 dB 01U HARKER 158717 nm 20 0 dBq 1 X Markef Bandwidt 31 7 fim 9 5 nm VB 3 kHz 1 RB 2 nm ST 20 sec Figure 3 Improved sweep times even for high sensitivity measurements that tradi tionally result in slow sweeps This plot shows the normalized output of an erbium amplifier filter that was stimulated by a white light source changed to reposition the signal in the measurement range of the analyzer s internal circuitry and the sweep con tinues This repositioning explains the pause that can occasionally be seen in a sweep with a wide measure ment range Chopper Mode The main purpose of the chopper mode is to provide stable sensitivity levels for long sweep times which could otherwise be affected by drift of the electronic circuitry The desired stability is achieved by automatically chopping the light to stabilize elec tronic drift in sweeps of 40 seconds or greater The effect is to sample the noise and stray light before each trace point and subtract them from the See Optical Spectrum Analyzer page 8 Non Chopper Mode Chopper Mode ST 41 Sec Figure 4 Dynamic range improvement from chopper mode WWW HPARCHIVE COM 1ST QUARTER 1994 MKR 1 WUL 1587 7 nm f 28 34 dBm TA 2 Logistics Data B
8. Recommended replacement of 5 volt regulators 5741 Incorrect manual procedure cannot measure resol B W accuracy 5715 Recommended replacement of 5 volt regulators 5742 Diodes w higher breakdown voltage improves focus reliability 5952 5 volt regulator reliability improvement on A6 pc board 5924 Recommended replacement of 5 volt regulators 5743 Diodes w higher breakdown voltage improves focus reliability 5953 YTF adjustment procedure 5938 Recommended replacement of 5 volt regulators 5744 Incorrect manual procedure cannot measure resol B W accuracy 5716 Diodes w higher breakdown voltage improves focus reliability 5954 Recommended replacement of 5 volt regulators 5745 Diodes with higher breakdown voltage improves focus reliability 5975 5 volt regulator reliability improvement on A6 pc board 5925 Option 462 6 dB resolution bandwidths 5955 RF attenuator with calibration ROM replacement 5688 RF attenuator retrofit kit HP P N 85680 60228 5689 RF attenuator with calibration ROM replacement 5690 RF attenuator with calibration ROM replacement 5691 Option 462 6 dB resolution bandwidths 5956 WWW HPARCHIVE COM BENCH BRIEFS SN SN Type No IO 8593E 01 IO 8593E 03 IO 8594E 01 IO 8594E 03 IO 8595E 01 IO 8595E 03 IO 8596E 01 IO 8596E 03 MA 8643A 01 IO 8643A 02 IO 8643A 03 MA _ 8644A 01 IO 8644A 02 IO 8644A 03 MA 8644B 01 IO 8644B 02 IO 8644B 03 MA 8645A 02 IO 8645A 03 IO 8645A 04 IO 8664A 02 MR 8664A 03 IO 8664A 04 IO 8665A 03 MR
9. andle could cause the existing ground path to open resulting in a possible shock hazard to the user Affected units must be retrofitted with grounding wires to rectify the problem Contact your local HP sales service office and your unit will be repaired free of charge For more information order the fol lowing Product Safety Service Notes using the HP FIRST FAX system Product Safety Service Note HP FIRST Doc ID No E3910A B 02 S E3939A B 02 S E4093A B 02 S E4095A B 02 S E4100B 02 S IDAC M XPE 02 S IDAC MPT 02 S oO BENCH BRIEFS 3 How is the Recommended Calibration Cycle Determined Jim Stead Hewlett Packard Introduction For T amp M products HP usually indi cates in the manual a recommended calibration cycle For many micro wave instruments this is typically a one year recommendation With calibration costs rapidly increasing longer calibration cycles are required to maintain a reasonable cost of own ership Following is an explanation of some of the steps involved in deter mining how an extended cycle can be justified Past Experiences Most companies maintain a database on past calibrations and can easily de termine what percentage of instru ments required adjustments This data is then used to appropriately change the calibration cycle HP maintains such a database for instru ments used in our microwave instru ment production facility As an example when the HP 8360 was in troduced
10. board assembly top and bottom shields 5939 Save A1 control board assembly top and bottom shields 5940 Part number correction for the A1 control board assembly 5941 Save A1 control board assembly top and bottom shields 5942 Upgrade address space for error map to 1 Mbyte 5760 New time delay fuse corrects intermittent fuse failure 5756 New time delay fuse corrects intermittent fuse failure 5757 Recommended modification to prevent possible shock hazard 5758 New fuse prevents output from sticking at 24 or 24Vdc rail 5759 Mod reduces Trig output levels when loaded with 50 ohms 5936 WWW HPARCHIVE COM 1ST QUARTER 1994 SN SN Type No IO IO IO MR MR MR MR MR MR MR MR PS IO PS IO PS IO PS IO PS 10 PS PS MR MR MR MA MA MR IO IO MR MR IO MR MR IO MR MR MR IO IO MR SM MR MA MA IO MA IO IO IO IO IO MA E2500B 08 E2505A 01 E2505A 02 E2550A 01 E2550A 02 E2755A 01 E3611A 03 E3614A 01 E3615A 01 E3616A 01 E3617A 01 E3910A B 02 S E3910B 01 E3939A B 02 S E3939B 01 E4093A B 02 S E4093B 01 E4095A B 02 S E4095B 01 E4100B 02 S E4240B 01 IDAC M XPE 02 S IDAC MPT 02 S J2213A 03 J2219A 02 11612A B 01 16092A 01 16099A 01 16339A 02 16500B 01 18281A 01B 18281A 02 34401A 03 34401A 04 35280A 01 35650A 01 35650B 01 35650B 02 35652A B 01 35665A 02A 37704A 01 37741A 01 37743A 01 53310 0194 01 66000A 02 70001A 17A 70004A 13 70301A 03 70320A 01 70320A 02 70320A 03 70322A 02 7
11. ch safety related service note is highlighted with a contrasting color HP E1401A VXI C Size High Power Mainframe Serial Numbers Affected 3227A00165 3227A00207 Build up of surface contamination in side the E1401A power supply plus a jumper wire with damaged insulation may cause a shock hazard to exist on an externally accessible pin on the rear panel of the E1401A Check your unit as follows Connect a voltmeter between chassis ground and pin 23 on the Sub D connector 1ST QUARTER 1994 on the rear of the E1401A Mainframe If a hazardous AC Voltage is present greater than 30 VAC RMS or 42 VAC peak your unit is hazardous A new power supply must be in stalled Order Safety Service Note E1401A 02 S document ID number 5758 on the HP FIRST system for more information E3910A B PT500 Protocol Tester Serial Numbers Affected 08 0000 CA33350292 E3939A B PT500 Protocol Tester Serial Numbers Affected CA32220000 CA33300023 E4093A B PT500 Protocol Tester Serial Numbers Affected 02 0000 CA33320025 E4095A B PT500 Protocol Tester Serial Numbers Affected 03 0000 CA33330209 E4100B PT500 Protocol Tester Serial Numbers Affected CA33130001 CA33150006 IDAC M XPE PT500 Protocol Tester Serial Numbers Affected CA32090001 CA33010010 IDAC MPT PT500 Protocol Tester Serial Numbers Affected 01 0000 01 9999 WWW HPARCHIVE COM High voltage applied to the connector module plane or connector module h
12. itter is normal for internal modulation source 5734 Cable replacement and identification 5776 Information on new firmware 5293 Firmware revision 1 1 increases trace capability 5750 WWW HPARCHIVE COM BENCH BRIEFS 7 SN SN Abstract HP FIRST Type No Document ID No MR 70908A 07 Mod reduces n x 300 MHz residual responses 5751 C MR 85032B 01 Corrections to spec errors in O S manual and customer letter 5926 IO 85620A 04 Module hangup is caused by improper programming 5746 IO 85620A 05 Downloadable programs may not be compat w earlier modules 5943 MR 85644A 02 Mod eliminates 1 MHz osc on output of tracking source 5927 MR 85645A 02 Mod eliminates 1 MHz osc on output of tracking source 5928 IO 86791A 01 Service manual update part number 86791 90004 5735 IO 86793A 01 New table provides correct ref designators during test 3xx 5755 MR 87510A 05 Modification fixes unexpected spurious problem 5738 IO 87510A 08 New key cap for power line switch 5921 MR 89410A 01C New FW fixes calibration timing problem 5710 MR 89410A 02 New analog motherboard improves channel match 5711 MR 89440A 01C New FW fixes calibration timing problem 5712 MR 89440A 02 New analog motherboard improves channel match 5713 Service Note Types IO Information Only MA Modification Available MR Modification Recommended SA Safety PS Priority Safety SM Interoffice Service Memo IOSM Optical Spectrum Analyzer continued from page 2 trace point reading In all modes
13. ller photodetector that has a lower noise equivalent power NEP Sensitivity can be set directly on Hewlett Packard optical spectrum analyzers which then automatically adjust to optimize the sweep time while maintaining the desired sen sitivity Sensitivity is coupled directly to video bandwidth as shown in Figure 2 As the sensitivity level is lowered the video bandwidth is de creased or the transimpedance amplifier gain is increased which re sults in a longer sweep time since the sweep time is inversely proportional to the video bandwidth The sweep time can be optimized because the video bandwidth is continuously vari able and just enough video filtering can be performed This avoids the problem of small increases in sensitiv ity causing large increases in sweep time which can occur when only a few video bandwidths are available in fairly large steps Tuning Speed Sweep Time Limits For fast sweeps sweep time is limited by the maximum tuning rate of the monochromator The direct drive ede a e AL 30 00 dBm Sensitivity Directly Settable FSENG lt 2 Be by the User P Sensitivity is defined as the minimum detectable signal or more specifically six times the rms noise level of the instrument Sensitivity is not specified as the average noise level as it is for RF and microwave spec Q trum analyzers because the average noise level of optical spectrum analyz CENT ers is 0 wat
14. of operation Hewlett Packard optical spectrum analyzers zero the detector circuitry before each sweep Improved dynamic range is another benefit of sampling the stray light be fore each trace point For measure ments requiring the greatest dynamic 8 BENCH BRIEFS range possible some improvement can be obtained with the use of the chopper mode While this mode does improve dynamic range it is not re quired for the analyzers to meet their dynamic range specifications Figure 4 shows the improved dynamic range obtained by activating All rights reserved Permission to reprint Bench Briefs granted upon written request to the Editor WWW HPARCHIVE COM the chopper mode This concludes the series on optical spectrum analyzers Bench Briefs wants to thank Richard Ogg Carla McCarter and Mike Levernier of the Hewlett Packard Microwave Tech nology Division Lightwave Opera tion for their contributions to this series o Bulk Rate U S Postage PAID San Jose CA Permit No 1201 Printed in U S A 1ST QUARTER 1994
15. ook 1994 Logistics Data Book John Cloutier Hewlett Packard If your work requires U S Govern ment National Stock Numbers NSNs for HP products and their components HP s annual Logistic Data Book and its companion micro fiche are must have resources The data book cross references HP product numbers to National Stock Numbers NSNs and Joint Electronic Type Designators JETDs lists con tract numbers for provisioned prod ucts and recommends replacements for discontinued products The com panion microfiche lists NSNs for product components and can be re quested with postage paid cards in cluded in the data books To obtain a free copy of the 1994 Logistics Data Book contact your nearest HP office or John Cloutier Hewlett Packard Company Federal Support Services MS 51U TH P O Box 58059 Santa Clara CA 95052 8059 o Safety Related Service Notes Service Notes from Hewlett Packard relating to personal safety and pos sible equipment damage are of vital importance to our customers To make you more aware of these impor tant notes they are printed on paper with a red border and the service note number as an S suffix In order to make you immediately aware of any potential safety problems we are highlighting safety related service notes here with a brief description of each problem Also in order to draw your attention to safety related ser vice notes in the service note index ea
16. s the HP 8510 sys tem Normal usage of a network analyzer requires that devices be con nected and disconnected to make measurements Over an extended time period this results in the connec tors being subjected to wear and or damage For this reason the HP 8510 recommended calibration cycle is li mited to one year and will probably never be extended Conclusions The recommended calibration cycle is just that a recommendation Operat ing environment and the user s appli cation are variables that cannot be included in the manufacturer s recommendation The published cycle should be used by the customer to help determine an initial calibration cycle Then an ongoing data collection process should be initiated to deter mine the best calibration cycle for the customer s application O 1994 Bench Briefs Instrument Service Note Index HP FIRST 208 344 4809 T amp M Section Press 4 Password Section Press 3 Password 76683 SN SN Abstract HP FIRST Type No Document ID No MA 3324A 03 New firmware must be installed with new A6 Signal Source Board 5708 IO 3456A 25 Clarification of product specifications and calibration cycle 5706 MR 3457A 17 Modification prevents shorting of multiple channels 5985 IO 3565S 07 Reprogramming required for use with HP 35630A B VISTA software 5977 IO 3577A 17 Source harmonic distn spec changed from 30 dBc to 25 dBc 5978 IO 3577B 07 Source harmonic distn spec changed from 30 dBc
17. t level self test 16 5969 Modification prevents rubber key from sticking 5970 Mod corrects PHASE LOCKED LOOP UNLOCKED error at high temp 5996 Option upgrade procedures 5997 Available option allows high speed option retrofitting 5014 LED board mod allows greater range of brightness adjustment 5929 LED board mod allows greater range of brightness adjustment 5930 LED board mod allows greater range of brightness adjustment 5931 Unusual power up seq can cause pseudo Fatal Error message 5719 HP 5071A performance test 5720 List of software revision A 01 13 anomalies 5900 List of software revision A 01 13 anomalies 5901 Safety compliance of RFI filter cap discharge time constant 5761 Safety compliance of RFI filter cap discharge time constant 5762 Mod reduces radiated RFI when replacing A2 HPIB board 5944 Mod reduces radiated RFI when replacing A2 HPIB board 5945 Mod reduces radiated RFI when replacing A2 HPIB board 5946 Mod reduces radiated RFI when replacing A2 HPIB board 5947 Mod reduces radiated RFI when replacing A2 HPIB board 5948 List of differences in mechanical electrical major parts 5949 Recommended replacement of 5 volt regulators 5739 Incorrect manual procedure cannot measure resol B W accuracy 5714 Diodes w higher breakdown voltage improves focus reliability 5950 Recommended replacement of 5 volt regulators 5740 Diodes w higher breakdown voltage improves focus reliability 5951 5 volt regulator reliability improvement on A6 pc board 5923
18. ts or minues infinity RB 8 dBm For more information on the differences between electrical and op Sensitivity 80 dBm gt SPAN 5 000 nm 1321 331 nm nn VB 200 Hz S 12958 nsec Figure 1 Display of signal with amplitude equal to sensitivity level Pub No 5952 3465 1994 Hewlett Packard WWW HPARCHIVE COM KA AL 60 00 dBn SENS 82 dBm 3 08 dB D LV Video BW 30 Hz START RB 1 nm 1150 0 nm VB 38 Hz STOP 1150 0 nm ST 10 sec Figure 2 Video bandwidth directly affects sensitivity motor system allows faster sweep rates when compared with optical spectrum analyzers that use gear re duction systems to rotate the diffrac tion grating For high sensitivity sweeps that tend to be slower the small photodetector and continuously variable digital video bandwidths allow faster sweep times The small photodetector re duces the sweep time because it has a lower NEP than the large photo detectors used in other optical spec trum analyzers Lower NEP means that for a given sensitivity level a wider video bandwidth can be used which results in a faster sweep Sweep time is inversely proportional to the video bandwidth for a given span and resolution bandwidth The continuously variable digital video bandwidths improve the sweep time for high sensitivi
19. ty sweeps in two ways First the implementation of digital video filtering is faster than the response time required by narrow analog filters during autoranging Second since the video bandwidth can be selected with great resolution just enough video filtering can be used resulting in no unnecessary sweep time penalty due to using a narrower video bandwidth than is re quired Figure 3 shows a 20 second filter response measurement This fil ter for an erbium amplifier was stimulated by a white light source and the figure shows the normalized 2 BENCH BRIEFS response The purpose of this filter is to attenuate light at the pump wave length while passing the amplified laser output of 1550 nm Due to the low power level of white light sources this measurement requires great sensitivity which traditionally has resulted in long sweep times Autoranging Mode Autoranging mode is activated auto matically for sweeps with amplitude ranges greater than about 50 dB The amplitude range is determined by the top of the screen and the sensitivity level set by the user With the auto ranging mode activated when the signal amplitude crosses a threshold level the sweep pauses the trans impedance amplifier s gain is Gp 12 25 46 JAN 24 1992 RL 3 20 dBm nm MKR 1oWUL 0 500 SENS ete 73a J dB 10 ap dB QIV A CENTER 1318 831 nm RB 1 nm VB 60
20. we looked at the data for a similar product the HP 8340A The data indicated that under normal operating conditions the recom mended one year calibration cycle for the HP 8340A was conservative i e 90 did not require any adjustments New Circuit Designs Design improvements are also used to justify extended calibration cycles Reduced parts count and fewer hardware adjustments mean there is less chance for drift or aging to have an effect on the calibration In addi tion newer circuit designs may pro vide better stability When compared to the HP 8340A the HP 8360 series has about one third fewer compo nents and about 25 of the HP 8340A hardware adjustments Long term ALC stability was also improved through the use of a Planar Doped Barrier PDB diode as the leveling detector User vs Self Adjustments Periodic adjustments are sometimes required for optimum performance To maintain an extended calibration cycle it is important that these adjust ments are either done automatically by the instrument or set up as user adjustments Both the HP 8340A B and HP 8360 series use auto tracking to maintain maximum RF output power In addition the HP 8360 series has both frequency span calibration and AM bandwidth calibration that fall into the user calibration category Mechanical Wear Sometimes the instrument or system environment has a large influence on the long term stability of the product A good example i
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