Donkey Kong 1981 Upright - Monitor

[Amoskeag]

Hello!

I am working on a Donkey Kong cabinet and I am getting a bad video signal. As I was playing around with it the video came to life and was working as intended (the game works and all just the video is the issue) Now It did go bad after messing with one of the potentiometers on the monitor, specifically the H-Center. My first instinct is this pot must be bad and causing the video to be warped like in the provided picture. After it came back to life and went bad again the video would be normal for a few seconds after power up, and then revert to the mess as seen. Could this be a different component that's the issue and not the potentiometer? Thanks for any and all advice!

- Amoskeag

[Gilrock]

I'm no expert but I wouldn't think a horizontal center pot would cause that.  It looks more like a Sync issue.  I use a Test Pattern Generator from CraftyMech to test monitors since that rules out the incoming signal.  The coming and going of the image could be it going in and out of sync.

[Amoskeag]

You are correct, I think it was simply a matter of correlation vs. causation. I reseated a bunch of the chips and the screen is back, but its flipping back and forth (upside right and the upside down) and beeping with each flip.

[Amoskeag]

Video of Current output: https://www.youtube.com/shorts/VxjFwsCVGz8

[Amoskeag]

I have made progress! Huzzah!

Looks like I am just missing colors, game runs well, entirely visual problems at this point. The Pots on the monitor did not bring the colors back as I expected so I believe this must be related to an EPROM not working right, any thoughts?

Cheers and thanks for assisting a newbie!

*EDIT*

ACH! How could I have missed that the 2E and 2F chips control the low 4 bits of the inverted palette colors and the high 4 bits of the inverted palette colors. I'm nearly sure that though I reseated them if I replace them the game will look perfect.

-Amoskeag