I can't imagine anyone pulling apart their tube amps every six months to check bias currents. I would guess this particular amp was in use for 40-50 years and outside of mom taking me to get a new tube for it once, it worked fine. If the Russian tubes are so poor as not to be trusted, I may try to hunt down some NOS parts.
This particular amplifier is slightly different than the schematic I posted. That was for some revision of the X-100-B. I wasn't able to locate the correct one but may end up marking up that schematic to match.
Restoring vintage tube equipment is a labor of love.
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But I sincerely wish you can complete your project.
Patience is your greatest asset here.
Thanks. The amplifier is basically working now outside of having a weak tube. Sounds like the problem is going to be sourcing a good set.
I've cleaned up the mechanical bits as much as I plan to. No polishing the parts. It's old and I want it to look and smell its age.
The wooden case is a different story. Waiting for the coating to cure, more wet sanding, more coats.... I thought I would have time this weekend to finish it up but ended up adding another coat. A few more days of dry time and I will have another look at it.
I think I posted about restoring my dad's old Garrard turntable. Now that thing took some time. I was very lucky in that case as someone had given me the exact turntable when I was a kid and for some reason I had saved it all these years. It was missing parts but was in good enough shape it made a very good donor. It supports LPs, 78s and 45s. You can auto change all record sizes. There is an adapter for the 45s. As a kid, we would stack 10 or so 45s on it. It will automatically place the needle and pick it up and does this for the record type selected. It's all mechanical and sorting that out took me a few days.
Once the amplifier is done, I still have the tuner to go through.