DK Monitor centering issue

DeLoreanRide

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I'm working on a supposedly good monitor for my Donkey Kong but I cannot seem to get the picture centered.

This is about the best I can get it:
DSC_0894.jpg

DSC_0893.jpg


Is this the horizontal hold pot? The Horizontal centering pot is new and seems to be in check.

The screen is sagging in the middle and I cannot center it vertically (or horizontally as the monitor says it). It just stays toward the bottom of the screen.

The B+ voltage is at about 109v.

Also it seems to me that I'm not getting any red color. I'm not quite sure where to start with that. All the pots on the neck board are new and as far as I can tell the three transistors on the neck board are good as well.

Think it's a cap kit? Filter cap?

Thanks for your help.
 
Last edited:
Try the H. Hold pot on the chassis behind the flyback.

Check the red output transistor on the neckboard. Check neckboard for cracked solder joints.
 
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The pots on the chassis and the game board are prone to failure. You can remove them and check them for smoothness with a DMM. If they are jumpy or no adjustment at all, replace them. Bob Roberts sells most of the chassis ones as a kit.
 
It seems as though I got it working. I swapped out the Horizontal hold pot, the B+ pot and started adjusting the game board pots.

The cable going to the monitor from the board was corroded on one end and the red was actually completely disconnected. Once I got all the colors working well the picture was much easier to adjust. It seems to be working well now.

Thanks everyone!

DSC_0898edit.jpg
 
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