HP-35 power unit: Failing Vgg voltage

[teenix]

It's amazing after 50 odd years, the board still looks new.

It is quite rare (that I know of) for a transformer like this to go open circuit, unless maybe it was subjected to shock, like being dropped. I would suspect a soldered terminal, as I think it would be unlikely to break somewhere in the middle of the coil.

It may be a long shot but re-soldering the transformer terminals from under the board might help.

If not, and you have a good magnifier, from the top side, you might be able to see a broken wire where it was soldered.

cheers

Tony