Older Channel Plus Modulator Problem

[handymantoo57]

I have an older Channel Plus Analog 3 Channel Modulator. Channel 3 flares with the screen has too much black. Anyone know what componet has gone bad?

 

[Pixl]

Try pulling it apart and measuring or substituting electrolytic capacitors.
I have two of these Channel Plus units in service over 10 years old, I'm lucky mine are not doing this yet.

 

[sergei]

I have an older Channel Plus Analog 3 Channel Modulator. Channel 3 flares with the screen has too much black. Anyone know what componet has gone bad?

Besides what Pixl suggested you might open it and post a picture of the inside as I've not seen what that model looks like and it might help some to suggest what could be wrong. I've repaired a couple of my Channel Plus 3025 and I'm not sure if they use the same board.

 

[handymantoo57]

Initially this unit developed static lines that affected all three channels. I discovered the +12 and -12 volt regulators were overheating as it seemed to function fine outside of the case when more air could keep it cool. I did replace both filter caps on the C channel also. I'm willing to replace more caps but I'd love to know what's technically not working. A schematic would be nice.

 

[FaT Air]

Since you say the video is flaring and the black is too black, suggests bias on a video amp is out of spec. caps will do that when they turn into resistors. Those caps above the center CA3086 IC looks suspect. Also the caps toward the bottom of your picture. I'd replace all of the electrolytic caps.

 

[sergei]

Initially this unit developed static lines that affected all three channels. I discovered the +12 and -12 volt regulators were overheating as it seemed to function fine outside of the case when more air could keep it cool. I did replace both filter caps on the C channel also. I'm willing to replace more caps but I'd love to know what's technically not working. A schematic would be nice.

I can't tell a lot from the picture and the board is completely different from my units. What you might try using is a hair dryer to put heat to different areas of the board to see if you can help locate the area with the bad part. Use a piece of cardboard to block the heat from other areas while your checking the board. If that doesn't work then leave it on to warm up to normal operating temperature and working and have yourself a can of circuit chiller, myself I use cans of Tech Spray Freezer 1672 that will chill down to -62 degrees and you can spray each component with the small tube.

 

[handymantoo57]

Flare fixed. I realized I was working on the A channel not the C channel since they are reversed when looking at it from the front. After changing the filter caps on the C channel the flare was gone! Thanks for all the advise.

 

[toucan-man]

Capacitors ? Us. Thanks for the update!