07-28-2014, 05:36 PM
You might have a gassy IF or converter tube. The negative voltage on the AVC line should not drop as the tubes warm up. If the voltage becomes less negative, then the positive current has to be coming from the control grid of the 6K7 or 6A8. You might try changing these tubes or removing them one by one and see which causes the negative AVC to drop.
The -3 VDC is the fixed bias on the tubes, which should become more negative by the rectified IF carrier signal from the detector. If it doesn't change with signal, then the 110 pF coupling cap to the AVC detector might be open, or there is just not enough converter or IF gain to produce the signal necessary to overcome the fixed bias and cause the detector to rectify and produce additional negative voltage.
The -3 VDC is the fixed bias on the tubes, which should become more negative by the rectified IF carrier signal from the detector. If it doesn't change with signal, then the 110 pF coupling cap to the AVC detector might be open, or there is just not enough converter or IF gain to produce the signal necessary to overcome the fixed bias and cause the detector to rectify and produce additional negative voltage.
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