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I've gone through and checked through all scope traces and voltages several times and everything is generally within spec, except for a few places.
The biggest anomaly is that the grid on the sound IF / sync amp should be, according to the schematic, -1.8V however I measure between -0.3 and -0.5V. The plate voltage should be 60V but I see about 54V when the set is cold, and it falls down to about 45V. When first powered on cold, I get actually watchable contrast and fairly strong sound, however... after it warms up for about 5 minutes the contrast, sound and to a lesser extent sync gets worse (as that plate voltage goes down).
I have tried no less than six different 6AN8 tubes and all the good ones are the same. Have verified and/or replaced all nearby resistors (nearly of the originals were still within 20% spec) and replaced all but the mica and ceramic caps. And still absolutely nothing from the AGC control. The DC voltages on the IF stages are pretty much right on.
What could be the temperature sensitive components that would cause that?
FK
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