Donkey Kong - intermittent video issues

capnswab

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OK, got a board repaired and am able to finally play some DK, but now seem to be having intermittant video issues. Sometimes it will turn on and I can play no problem, sometimes it turns on and looks like the attached image. Even if the screen looks OK, and I try and adjust anything on the monitor or the board, it turns into the attached image. Typically, I restart it a few times and it comes up. Also, it seems horizontally, the image is always a bit wider than the screen when everything comes up.

Am I up for a monitor cap kit next? Discharging these things seems scary...
 

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Inspect the pots on the board, see if they got damaged in shipping. Were they replaced with new ones? The old pots are notoriously flakey.

-Ian
 
Could also be in the monitor, if the horizontal width coil is adjusted way out of whack, or the horizontal hold control is flaky or adjusted just on the edge of working.

-Ian
 
adjustment

Find the manual for your monitor and locate the horizontal hold.. adjust it slowly until the picture is clear. It will take 30 seconds to complete. :D
 
I would check the pots on the game pcb first. If either has a broken leg it can cause issues like this. Also clean the headers for the power interconnect cable(rainbow cable).
 
Pots on the video board appear to be OK, no broken legs. It's kind of touch and go with the video, I've been able to play last night and this morning no problem. Just to make sure, is the horizontal hold pot the one next to the horizontal width coil? Or is it the white toggle looking one in the middle of the board?
 
Just to make sure, is the horizontal hold pot the one next to the horizontal width coil? Or is it the white toggle looking one in the middle of the board?
Yes. The toggle looking thing is the service switch, it collapses the raster down to a horizontal line.

-Ian
 
Also, that H-Hold pot is notoriously flakey. I had one that I could dial in, but it took 10 minutes of trial and error (nudge pot, check screen, repeat) before I could get it right. Replacing the pot fixed it and made adjustment 1000 times better.
 
After much fiddling, I think I found the sweet spot on that thing. Been fine the past few days.

Now on to the width issues...adjusting the width coil doesn't seem to do anything...
 
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