Apple //c video "interference"

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Joined: Oct 22 2014
Posts: 33

In this linked photo you can see a rolling "interference" through the display.

This only occurs when the //c is on, but not while just the Monitor //c is on.

It does appear to be more shaky and will distort the text characters on floppy read/write.

Is there a filter/capacitor/component that is responsible for this type of effect that I could replace? I don't know if it's relevant, but I do use one of these as my power supply for the //c

Thanks!

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Joined: Oct 22 2014
Posts: 33
Re: Apple //c video "interference"

As a quick follow up

I've tried two different cables, neither is better than the other. I threw the picture up on another TV with similar results, so I definitely think it's the //c itself.

As a test I removed the logic board and connected the two wires to the two connectors of the RCA pins on the board, just to make sure the connector itself wasn't tarnished or damaged. Same result. This reminds me of a ground issue, but I have both the computer and monitor on the same outlet.

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Joined: Oct 22 2014
Posts: 33
Re: Apple //c video "interference"

So 1 more update, I hooked up the "monitor" to a small media player I have, since it's just an NTSC compatible display device. Works flawlessly.

I can then narrow it down to two things. Either it needs a seriously shielded cable, which I will test tomorrow when it arrives -OR- that aftermarket adapter uses some kind of floating ground (not from the wall) and there's a ground loop.

The odd thing is that my small media player does not seem to have a ground prong, so surely those run off different grounds.

We shall see tomorrow.