Quote:
Originally Posted by rca21d645
So I have the picture looking pretty good but the audio is now quieter and there's a loud hum drowning it out. I think it has to do with the vertical because turning the height and linearity controls makes the hum quieter.
Edit: upon further inspection it appears the audio output tube had gone bad between now and when I started this project, as the emmissions now test bad.
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The voltage on the cathode of the audio output(pin 1) supplies 135v to the audio IF, tuner, video IF, and video out circuits. Basically the tube is used as a b+ dropper to supply the lower b+. If you operate the TV with the audio output tube pulled, those other circuits will loose their b+. Good to verify that 135v volts is in the ballpark.
01-27-2021, 11:34 AM
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