RCA 8TS30 problems

[Ralph S]

I've just finished working on an 8TS30 chassis but have hit one snag that's really a bear: Video gain is erratic and unreliable. I've been through the entire circuit over and over and have replaced all paper caps, electrolytics and a great number of resistors and micas. The quality of the video is excellent but keeps popping from one setting of the contrast control to another. I'm trying to get a new control from Moyers but haven't heard anything back yet. Also, it may be possible that there is an intermittent short in the CRT which otherwise tests excellent. Other than the possible problem with the CRT, has anyone had this problem with this chassis or its close cousin, the 630 chassis?