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Last Updated: March 26 2021 17:51

Test Gear Maintenance

As you can see in the 'about me' section of this site my workshop is equipped with a variety of antique test gear. Most of this has come from places like radio rallies, EBay and, believe it or not, out of skips. Large manufacturers and suppliers of radio and electronics have to keep up to date with the latest in test gear. In many cases the 'old' stuff has long since been written down, so in the books it appears to have no value. Disposing of such 'valueless junk' is often an expense that is kept to the minimum by simply ordering up a skip (for American readers - skip = dumpster) and heaving the whole lot in. I guess millions of pounds worth of often only slightly out of date stuff must end up in landfill every year.

This is really a crying shame, and sometimes engineers (often with tears in their eyes!) retrieve these abandoned items, restore them to their former glory and allow them to live out their twilight years giving useful service to amateurs (like me!) Obviously this gear often has faults, but back in the 70s and 80s when this stuff was built they often used discrete components, the most complex chips used were 741 OpAmps and 74 series logic chips. This makes this sort of stuff possible to service by amateurs at home.

Notable examples in the G1SLE workshop are:-

HP-3580A audio spectrum analyser - bought as 'dead' on EBay for 35.
Fault - internal mains fuse blown, fixed in 5 minutes and now a very handy instrument for all sorts of AF work, especially modulation response analysis and that sort or thing.

Racal 9081 520 MHz signal generator - heaved out of a skip.
Fault - OC plated through hole on 540 MHz oscillator PCB, fixed in an hour and now very handy as a second RF source in conjunction with my...

Schlumberger 4040 test set - bought at Leicester radio rally - 2 for 400 - "Oy mate, you forgot this Code Analyser thing, it's in with the price"
Very nice transceiver test set from 0.4 to 960Mhz RF gen, power meter, mod meter, 2 x mod sources, 5 tone, adjacent channel power etc. etc. Both working and a very handy bit of kit, as was the...

Schlumberger 4922 Radio Code Analyser - apparently free with the 4040 test sets.
Very flexible mod source and decoder. 2 generators 10Hz to 30 kHz, FFSK encode/decode, Selcall and DTMF encode/decode, MPT1327 testing (when coupled with 4040 test set) - even does telephone pulse dialling - though I have yet to find a use for that! Arrived in working order.

HP141t Spectrum Analyser
Until recently the G1SLE shack sported 2 of these, one with the 8553/8552B plug-ins and the 8443a Tracking Generator for 1kHz to 110Mhz and one with the 8555/8552B plug-ins, 8445b Tracking Preselector / Digital display and 8444a tracking generator. These units are 'modular' a complete analyser being made up from the display frame, 1 x RF and 1x IF plug-in. I bought mine a bit at a time on EBay, usually faulty and for reasonable prices. One display had a dry capacitor making it unstable, an 8555a (usually very expensive) 18Ghz plug-in was deaf by about 30dB - this was traced to an OC coupling loop in the first IF filter. Recently the 141 frame that I normally use on 0.01 - 18 GHz has been replaced with...

HP8565 Spectrum analyser. - Bought cheaply on EBay listed as 'blows mains fuse'
Appeared to have been labelled as "240V" but jumpered as 110V. This had resulted in several faults in the PSU section, but the whole thing was fixed in only a few hours using < 5 of parts. This is now my main microwave analyser - covering 0.01 to 22 GHz and working nicely with my HP-8444a tracking generator for frequency response testing up to 1300 MHz.

Repairs to this sort of stuff are much easier if you have a service manual. I have picked up manuals for much of the stuff above in .PDF format. These are available for free download below. Alternatively you could pay money for them on EBay!

Filename Filesize Model Description
hp3580a.pdf 15.2 Mb HP 3580 Spectrum Analyser Service Manual
141t_service.pdf 5.4 Mb HP 141T Spectrum Analyser Service Manual
8552b.pdf 11.5 Mb HP 8552B Plug-In Unit Service Manual
8553b.pdf 31.5 Mb HP 8553B Plug-In Unit Service Manual
85558_service.pdf 5.6 Mb HP 85558 Spectrum Analyser Service Manual
hp8445a.pdf 15.4 Mb HP 8445A Automatic Preselector Service Manual
HP-436a.pdf 4.9 Mb HP 436A Power Meter Service Manual
hp8443a.pdf 37.6 Mb HP 8443A Tracking Generator Operating & Service Manual
hp8444a_v6.pdf 2.7 Mb HP 84434 Tracking Generator Operating & Service Manual
hp8554b.pdf 35.3 Mb HP 8554B Spectrum Analyser RF Section Operating & Service Manual
hp8555a.pdf 14.2 Mb HP 8555A Plug-In Unit Technical Manual
436_service_6.pdf 7.2 Mb HP 436A Technical Manual
9081_82MM.pdf 6.8 Mb Racal 9081/9082 Signal Generator Maintenance Manual
tf2370ds.pdf 1.7 Mb Marconi TF 2370 Digital Schematic
tf2370pl.pdf 959 kb Marconi TF 2370 Parts List
tf2370umm.pdf 3.0 Mb Marconi TF 2370 User Maintenence Manual
tf2370rfs.pdf 1.3 Mb Marconi TF 2370 RF Schematic

Yes the list is not complete, and yes it would be nicer to have them as nice ring bound books, but the .pdfs are a good start and are much better than nothing.

Finally, if anybody can help I'm still looking for service manuals for:

  • Schlumberger 4922 Radio Code Analyser
  • Schlumberger 4040 Communications Test Set
  • EIP model 535 Microwave Frequency Counter.
If anybody has these available in electronic form please let me know using the contact me form on this website.

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