Philco Roundie on going repair

[blue_lateral]

Originally Posted by southernguy

The Video is back but the green is at full blast with retrace lines and the green screen control has no effect while blue and red seem to be uneffected. Im worried it might be the delay line but im not sure. CRT test ok. This weekend I hope to pull the chassis and take some measurements. So I'm up for sugestions.

Maybe before you pull the chassis, take some voltage measurements at the crt socket. Avoid pin 9 (focus) becuse there is a lot of voltage there (6000v?). Note that the screens can be around 600-900v. Use appropriate caution. This could give us a lot better shot at guessing.

In some sets heater to cathode shorts in the crt can turn on one color full blast. I have never seen this in a ctc-15 like set, and I dont think it would happen because the cathodes are almost tied together. Does your CRT tester check for h-k shorts? If not, an easy way to test it would be to put a brightener on it if you have one in your junk. The most common kind of brightener for a roundie is also an isolation transformer that will "fix" h-k shorts by isolating the filament. There is a switch on top that allows you to run the filament on normal voltage (no boost). This is kind of a long shot anyway, because I think all 3 colors would be on full blast.

An open green drive control could do it I think, or an open green screen control. Unfortunately I dont have a schematic handy right now.

I'm pretty sure a delay line couldnt do this. You would either have no video, or severe ghosting I think. In any event delay lines can be replaced with a clipcord for a test, and the chroma and video will work, but not land on top of each other correctly.

Could one of the crt wires have broken loose from the chassis? This has hapenned to me more than once.

Good luck

John