Issue with an LC monitor (12” RGB): Interference / Horizontal Lines

[Scott Baret]

Monitor has interference when cursor is moved or new text appears. This comes in the form of horizontal lines that are light gray against white. It's not an ADB issue due to modifier keys not causing this problem.This usually only happens or can be noticed on blank white screen.The monitor seems fine otherwise.I'm guessing potentially the boards/caps, potentially the fact it's on a circuit at an apartment building when many people have A/Cs running. Never have had this issue until recently.

I do have a spare board with new caps to swap in if need be, but I'd like to rule out anything else first--specifically the CRT itself.Thoughts?

I'm hoping it's just something on the boards since I do know an analog board swap has fixed similar issues on compact Macs.

 

[Scott Baret]

Update on something weird: I opened the Mac up, disconnected and re-connected the power supply, then moved the monitor off to the side and disconnected the ADB chain. No interference! I reconnected it. Again, no interference. Then, I put the computer and monitor on top of each other as usual. If there's any interference there, it's only me looking too hard and seeing what probably is just normal CRT behavior.

This Mac had some sound issues when an Apple II card was installed, and it seems the Apple II card had done something to the logic board where it would short things out. I felt getting rid of all connections may help.

LC is re-capped so caps aren't the issue on the main board.

Any more ideas? Any way to prevent this in the future?

 

[bibilit]

The LC card should be recapped as well (two capacitors)