RCA 8TS30 - no picture

[Gleb]

Originally Posted by bigaudioal

Tested a few resistors along the way (all tested within spec) and finally came to a 270pf mica cap AT the tuner. I usually ignore micas, but decided to replace this one for the hell of it. BINGO!!!

What's the capacitor's number according to the schematic diagram? It's strange that there was no any picture when you injected a signal into the video amp.

[bigaudioal]

Originally Posted by Gleb

What's the capacitor's number according to the schematic diagram? It's strange that there was no any picture when you injected a signal into the video amp.

I was thinking the same. All I was getting was a white raster. Contrast control was having zero effect on that raster too. When I tried to inject in the video amp, the raster did change some. Saw a wide dark band (maybe 4-5 inches high) that flipped very slowly vertically. But was not really discernible as a picture.

According to the SAMS (set 54, folder 18) I replaced C21, which is an IF coupling cap.

[Kevin Kuehn]

C21 shorted would place B+ on the grid of the first video IF amp, which would cause it to draw excessive current, thus pulling the B+ line low. That same B+ buss feeds all the video IF tubes,video amp, and the video output. If I'm not mistaken Kamakiri was having issues with something intermittently pulling that B+ low.

[bigaudioal]

Originally Posted by Kevin Kuehn

C21 shorted would place B+ on the grid of the first video IF amp, which would cause it to draw excessive current, thus pulling the B+ line low. That same B+ buss feeds all the video IF tubes,video amp, and the video output. If I'm not mistaken Kamakiri was having issues with something intermittently pulling that B+ low.

I cannot remember the issues Kamakiri had with this set after the recap. But glad I decided to trace that circuit back. I figured looking at the schematic that it sure looked like this circuit was feeding the IF and video sections and since I was having issues with both that it seemed more than likely the issue was there someplace. Set was rock solid after 2 plus hours viewing late last night.