Wells Gardner 4900 driving me crazy

[joeleonard]

All, I am new to this forum, and to repairing arcade equipment, so hopefully I don't irritate too many people. I am repairing a Ms Pacman for my son's school it has a WG 4900. I have done a cap kit and changed Vertical output trans Q302 and Q303. Once I reinstalled the board the picture was beautiful color was good, perfectly stable perfectly square. The problem came in when I tried to reinstall the chassis, everything went wonky the screen flickered from left to right and no adjustment helped. I yanked the board out again. R313 checks out ok, I assumed I screwed up by not using the 'gasket' on Q302 and Q303 (although I did use grease).
Reinstalled new vertical transistors with the gasket, with grease, checked voltage regulator at IC501 for bad joints, reflowed a little solder there. When I plugged it in today it looked great, I thought I had it figured out until I turned the unit off, when I turned it back on it went wonky again, a large 2" band runs from right to left, the unit hums too.
I checked the voltage at ic501 it read 130 on the money, the collector reads 150V though, not sure if that's in spec.
I am kind of at a loss. Can anyone kick me in the right direction?
my two guesses are heat related or a bad ground but I am not sure where to check.
My son's school and I appreciate any help anyone can offer.

[buffett]

Q302-303 do not use the insulators they screw directly to the heat sink's.

check your solder work and look for broken traces in the area.

Peace
Buffett

[joeleonard]

Thanks Buffett,

I dug in last night checking all joints and traces in that location, found a few that could be flakey. I'll take the insulator off of Q302 also. When I install the board again (tomorrow since I have to work on it at the school during school hours with a bunch of curious kids around ;-P) I am going to check all of my grounds really carefully and pray a little.

[joeleonard]

Just wanted to follow up, i worked on Ms Pacman today, installed the WG but it was still funky, finally after thinking about the hum and having no other options but to investigate I started wiggling wires. I finally got to the game board and with a slight tweak it all came into focus. I still have a hum bar which I will tackle Monday but at least for now it's playable and I feel pretty good that it is fixed for good. Thanks Buffett for the input. This is a really fun hobbie 

[buffett]

no prob happy to help.

glad you found part of the problem.

for the hum bar try removing the ground from the monitor frame.

if that does not work then it may be a power supply problem.
change it or rebuild it to see if the problem goes away.

Peace
Buffett

[joeleonard]

I replaced fuses today no change. Weird thing, I noticed touching one of the test points near the vert hold made it even worse, it was kind of funny to watch. The machine has the filter PCB, I have read it's best to just yank it out but I didn't look at it hard enough to know if the connections before the board were compatible with the connections on the board or how I'd connect the harness without the filter.

[buffett]

if it is going nuts when touch touch things on the chassis then you still have a problem with it.

my guess is its a broken trace or a bad solder joint.

i had one like that that needed 17 jumpers.

so look closely at the traces. you may also need to flex the board wile looking at it to see the breaks in the traces.
and use a meter to verify continuity.

are the fuse holders in the cab original??

if so replace them even tho they look fine. pac/mspac cabs had crappy fuse holders.
they cause all kind of weird problems.

when you take the filter board out just install the harness directly on to the PCB.
the filter boards are not needed and cause all kinds of connection problems.

Peace
Buffett