WG 25K7191 problems (post cap kit install)

[xyrts]

Hello all, I have been working on a Wells Gardner 25K7191 board. I just stuffed it with new caps, a new flyback, and a new HOT (Bob's kit) which fixed one of my major issues (found one of the larger caps to be open) but still have problems with horizontal sync and vertical throw. Adjusting the vertical position pot all the way to one end cant quite bring the picture down far enough to fill the screen. The other problem is that the top inch or so of the screen is out of sync. When adjusting the horizontal sync pot it is hyper sensitive but only seems to effect the top 2 inches of the screen and never quite becomes straight.

http://www.flickr.com/photos/35057739@N05/3254072194/ (picture of horizontal sync issue)
http://www.flickr.com/photos/35057739@N05/3253245895/ (same up close)

Any help is greatly appreciated,
Tim

[xyrts]

It looks like one of the new caps I put in might have been bad because I looked back at some video I took (when I was trying to diagnose an issue that turned out to be an open cap) and the sync problem at the top 1" of the screen is not present. Sadly I only tested the caps I took off the board and not the ones I put in it. Lesson learned I guess. Otherwise the other issue of the screen being projected too high vertically was present before and after stuffing the board and I still have no idea where I should be looking for that one.

[xyrts]

Looks like a just opened up a whole can of worms. I started tracing through the schematics to try to figure out what was on the board from the factory vs. what was a doping job by a previous owner (mostly in the vertical hold/size circuit) and after taking some of the modifications off and restoring some caps and resistors to spec my picture is now way off (picture is now flattened vertically to about 4 inches in the center of the screen with a big tear coming in from the left side of the picture). I am starting to wonder if there are any variances from the k7000 schematics that might have made it onto the board from the factory? I know for a fact that this board has been doped by somebody in the past, its just hard to tell sometimes what might have been modified before it left the factory.
Tim

[Ken Layton]

i've said it lots of times before, Wells-Gardner made undocumented production changes to the k7000 series. These were usually done on the foil side of the board. There are some resistors and capacitors tack soldered to the foil side. It may look amateurish, but it was done at the factory.

If you encounter a chassis with resistors and/or capacitors soldered to the foil side, LEAVE THEM ALONE!

[xyrts]

I finally had a chance to work on it again today. I'm a little embarrassed because I quickly figured out that I left a cap off the board last time I worked on it which caused the previous picture shrinking problem. Unfortunately the horizontal hold is still messed up on the top of the screen. Sometime tomorrow I am going to pull and test all the new caps I stuffed the board with. Hopefully one of those was defective and that is causing the problem, otherwise I have no idea.  Also I am still unable to get the picture to come down to the correct position vertically regardless of everything I have tried so far.
Tim

[xyrts]

I just tested all the caps, all the resistors, all the diodes, and all the transistors on the board. Everything was fine. I am at wits end with this thing. Only thing I can think of is the new flyback I got from bob is somehow defective. Gonna put the old one back in tomorrow and see what happens. Anyone have any idea what the voltage across the yoke should read with an ac meter? Also the voltage above the ground on the yoke?
Any help would be greatly appreciated...
Tim

[Kevin Mullins]

Unfortunately the horizontal hold is still messed up on the top of the screen.

So if I'm understanding correctly it's just the very top of the screen that seems out of wack?

Have you tried adjusting the vertical size down a little?

Have you tried adjusting the 50/60hz pot a little?

Is the B+ at the correct voltage?