K4900 Monitor issue

[slammin]

Hi and thanks for reading.  I am pretty new to this kind of stuff, but I'll try to provide as much info as I can.  I have a WG k4900 monitor that I pulled from an old Reactor machine that had been retrofit with a Vigilante board.  Game works great, monitor has a strange Vertical issue (see pic attached).

I reflowed solder in the vertical area, no change.
I recapped the chassis, but the problem remains.
B+ tested at 129.2V. 
I have checked the board over quite thoroughly for continuity on the traces. 
I was going to replace the vertical deflector transistors Q302 &Q303, but I read that they are rarely the cause.  I also tested voltage drop across B-E and B-C at about 6.5v, not sure if that's ok. 

Video sync is ok, Jamma uses composite neg. Vert. and Hor. sync.

Instead of just throwing parts at it, I figured I'd ask the experts on which direction to take next.

  I have not been able to find any monitor issues exactly like this one.  I've seen others that are similar, but usually have a black bar in the middle, or a duplicated image, but not overlapped.

Thanks for any suggestions.

[grantspain]

it could be as simple as a vertical hold or shift pot
when testing k4900 i use a negative h sync only

[slammin]

Thanks, I'll try testing the Pots.
I should also mention that the image is stable, it's not rolling.

[grantspain]

on many chassis having the v and h sync linked will cause odd issues so keep that in mind, it's a 2 second job to prove

[slammin]

Ok, so I fixed the issue.  Did a few things to the board:

1) removed Q302 and Q303, they tested fine, so I put them back in after applying some new thermal paste.
2)I removed and tested R313, which tested @476 ohms, reinstalled
3)removed and tested pots: V.line/damp, V.shift/position and V.hold. all tested ok, cleaned with isopropyl alcohol. "wiped" and reinstalled
4)removed and tested transistor Q901 on vertical position board P344, tested ok, reinstalled.

I did try removing the neg V sync, but it made no difference.

So one of those things did the trick.

Vigilante is almost square in it's display, so it looks like something is wrong with the width, but you can see with the street fighter board that it's just the aspect ratio.

Thanks again for your help grantspain and hopefully this post will help someone with the same issue.