sylvania roundie D01

[DaveWM]

did the standard startup routine, HV came up and sound, extremely weak pic and no sync lock. AGC super critical. Pulled the chassis in, checked the caps around the AGC, all checked good. replaced 5 or 6 tubes, mostly shorted 6GH8's and a 6JT8 that is part of the AGC. Replaced a few crumbling cheapo tube sockets on the chroma board (only the metal sockets remained).Tried it again, no audio or video, just some odd thermin like sounds... You could here the tuner snow start up then it would go off. Pulling the HOT would let the tuner work so I figured it has to do with the keyed AGC.

Put the old 6JT8 back in and works again (dual purpose tube, triode section is the AGC keying pentode is the video amp), but AGC is still super critical and both vert and horz sync are very weak. the orig 6JT8 was very weak, the new tube tested fine, so I am going to look there again. there is also a noise gate transistor that is the very early style, rectangle shape NPN. It looks like it would be a likely candidate for screwing up the bias of the sync separater. There is a wave form on the sams at the collector of that transistor so that will be the 1st place to check.

after the replacement tubes and socket fix the color demodulation is working. this set has a lot of the maroon drops, I expected to find a lot of bad ones but after testing several, they seem to be fine. the only weak one was in the chorma section grid coupling the 6GU7, just like on all the RCA's (this is NOT a RCA clone).