RCA 8TS30 Negative Image

[Chris K]

Originally Posted by Penthode

Your set does not have AGC. With the contrast control fully clockwise with a strongish signal, it is supposed to go negative

My pattern generator has adjustable RF output gain. If I lower that will it help? I don't think my contrast pot is working anymore. It was making a slight grinding sound. Now it's really not doing anything.

The issue now is I can't get a picture that's stable. Twitches...momentary brightness and focus changes...great picture if I wiggle no specific control for a second...then back to twitchy crap...tap on the focus coil, picture looks good for a second then goes to crap etc. There's just a general instability I can't track down. It's not the CRT...same thing on 2 different 10BP4s (and on my 5" tech CRT). It's not the pattern generator...I've used 3 different ones...same thing. Maybe I should try a broadcast signal? I don't think that's going to cure the symptom. It seems to be an issue at a much more basic level. Tuner has been cleaned...tube sockets have been cleaned...very frustrating.

I wish there was some way to post a video of how it's behaving. It's a lot easier to display than it is to describe.