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Old 9th Apr 2021, 10:45 pm   #10
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Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,172
Arrow Re: Pye 8440 stabilised PSU

Woodchips: I would make the effort to restore it - although I appreciate that the (probably) extensive effort to do that must bear a sane relationship to the use you are then likely to give it.

By what you've said, it sounds like all it needs are replacement valves - and then - presumably - adjustment & calibration. The big Q. is what valves does it need? In the absence of appropriate technical literature for this PSU, it's time for some detective work. You need get stuck in to the wiring and try to trace out as much circuitry as possible: the object being to discover what valves you can fit in to make it work, even if they are not the original types. I don't know, but I suspect on account of the age of this item we are talking about International Octal based valves for rectifiers and pass valves.

Typical candidates, rectifiers.
5R4, 5U4, 5Z4, GZ32, 33, 34, 37. (All Octal based).
It'll be a question of measuring the H.V. output from the mains transformer: determining just how max. d.c. current the transformer will deliver.

Typical candidates: series pass valves.
12E14, 12E1, 6080, 6L6, KT88. (All Octal based).
Again, it will be a question of max. d.c. voltage input that a given valve can accept and max. d.c. current it can pass.

Typical candidates: stabilizer valves.
0D3, VR150/30 (Octal based),
5651 (English Electric Valve co.), B9A based,
85A2, B7G based.

It's almost certain that some degree of modification of the existing circuitry will be necessary with any on those choices, but if you can trace out a clear block diagram of how the major components inter-connect with each other and determine certain critical values of some components, voltages and currents, you should be in with a fighting chance - but this will certainly not be a 'five-minute job'!

And I wish you the very best of luck!
Al. / Apr. 9th.
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