RA103-D has strange issue(s)

[DavidGoncalv]

How does it measure up when you do resistance/voltage checks against the service notes?

[zeno]

I dont have much experience pre 1960 BUT
it sounds like you have an AGC problem causing it all.
Too much gain will clip the hoz sync pulse & tear up the pix.
Also causes sometime audio buzz, jittters, over contrast,
negative pix........
Start with adusting AGC then tube then any caps not changed
in the AGC area. Also high ohm resistors working your way down..

73 Zeno

[Phil Nelson]

I believe the RA-103D is like RA-103 in not having AGC. On the 103, the contrast control varies the gain on the 1st and 2nd video IFs. As I understand it, the contrast acts as a manual gain control, like the "picture" control on an RCA 630TS.

Re your main question, the instability and drifting of the gain doesn't sound typical for this model. My RA-103 is one of the most stable early TVs in this house. The whole set seems rather over-engineered, apart from the Focus pot, which is a notorious weak spot.

Phil Nelson
http://antiqueradio.org/index.html