[Central-Electronics] 20A 6AG7 voltages

[k6jek]

Folks,

The plate and screen voltages on my 6AG7's are too darned high, at least I think so.  Do you guys see 300 V or something greater?  The bias seems correct, -10V.  I have the AC cranked down to 110 and still see 375 VDC on the plates and screens.  Yikes, I say.  Yikes.

BTW.  Dave, K6IR, solved the mystery of the screen resistors which none of the rest of you guys seem to have.  They were in the early, early, early 20A's.  He came up with the original wiring diagram and there they were.  There were no parasitic chokes on the plates of the 6AG7's. The grid resistors were 100 ohms, not 15, and the screens were fed with 180 ohm resistors both fried in my unit. And, of course, the oscillator is 1/2 of a 12AU7a, not a 6U8.  All this was changed after just three months of production.

One more thing.  Dave has the early wiring diagram.  I don't suppose any of you actually have the early schematic, first version, 1954, not the revised version on BAMA.  I can figure things out from the wiring diagram but a schematic would make it easier.

Thank,

Jon