I have a 1967 Zenith color set with chassis 24NC31Z. Every once in a while, the contrast seems to flicker darker and lighter. I've adjusted the AGC control down. Are there some tubes in that particular circuit that I should check?

Thanks,
Frank

if the agc is super critical in adjustment I would check a 5uf cap somewhere in that circuit. if the AGC react normally to adjustment then check the electrolytic in the contrast circuit, part of the video out IIRC.

6BA11 is AGC tube. Best test is light tapping of tubes
while watching picture. If you find a sensitive spot
try cleaning socket first. Changes in contrast can be
anywhere from the tuner through the IF's, video amps & AGC
you really gotta see it to tell.
I have the manual out if you have any more questions.

73 Zeno:smoke:

Thanks. I'll check it out and let you know what I find.

Frank.