K4600 Vertical Hold Problem

Rich in FL

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Hi Everyone,

I am working my way through fixing a bunch of monitors I picked up a couple of weeks ago. Most of the 4600s I've fixed work great now, but I have 2 K4600s that are giving me a weird problem that has me stumped. I hope someone out there knows how to fix the problem.

The image looks good after capping the monitor, but I can't get the vertical hold to lock in nice and steady. The image will hold still, but will jerk a little every 5-10 seconds and occasionally roll once or twice before locking in again. It looks like the monitor is jittery for lack of a better description. I have recapped it and adjusted the pot on the XY pcb with a plastic screwdriver as suggested on the net.

Your advice in correcting this problem would be greatly appreciated.

Thanks, --Rich
 
Sorry, I forgot to mention. I have already reflowed the pins for the 2 daughter boards and the power board on main board when I installed the new caps. Thanks for your assistance in diagnosing this problem. --Rich
 
I have recapped it and adjusted the pot on the XY pcb with a plastic screwdriver as suggested on the net.

Well, the screwdriver adjustment mentioned here is for Horizontal Hold issues, not Vertical Hold issues:

http://therealbobroberts.net/slanted.html

So, if that is the pot you adjusted, you adjusted the wrong one (unless your problem is actually Horizontal.) The Vertical Hold pot it the big black one in the middle on the X/Y card, and can be adjusted with your fingers.

Now, if the problem is definitely vertical, start by checking the transistors in the vertical section of the X/Y card (the board has a line separating the vertical and horizontal sections). The Hold pot itself may be dirty or bad. Check the diodes there, too.

If your problem is Horizontal, check R360 to see if it is 27-ohms. Then check the transistors and diodes in that circuit....
 
Thanks for the advice guys. I'll dig back into these monitors and see if I can find the solution to the problem. I appreciate the help. --Rich
 
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