Monitor goes from full color to grayscale-ish. what is loose?

[kcm3]

Hi all,

I'm having a weird video problem in my latest cabinet. The picture will look just fine, and then suddenly it becomes all grayscale, almost white. It's like a very bright, washed out white. You can still see most everything that's going on, but you can't differentiate colors.

I've determined by coincidence that this change can be both caused and fixed by a hitting the side of the cabinet with my fist, which tells me that there's probably a loose wire somewhere that's popping in and out.

I don't know much about video though, so I'm not sure what wire can cause everything to go white like that. There's nothing "obviously" loose, so I was hoping you guys might be able to help me narrow my search. Not necessarily for my specific monitor, but in general, what is the symptom that I'm seeing, and what can cause it. Although, I'll post the monitor specifics below in case they are helpful.

I'm not sure what particular model my monitor is, actually. It's some kind of Wells-Gardener, but the number that appears on a label doesn't seem to be a model number. It's "WG 1580971". I assume that's a serial number or something. Other numbers that I could find on the board in large-ish lettering were "WGM2574", "P763" and "P719-1". Does that help identify what monitor this is? I can post some pictures of it if that would be more useful.

This was oringinally a Marvel vs Capcom, in a pretty generic seeming cabinet. This problem has occurred all along, even with the MvsC PCB in there, so it's definitely in the monitor wiring, not my computer/video card setup.

Any help you guys might be able to provide wold be great, as I'm having very little luck going at the wires by trial and error so far.

[menace]

I just recently had a color problem and this is what I looked at on my K7191.  The three transistors on the neckboard--check for loose connections or sometimes they have busted legs if someone has wiggled them too much in the past.  check your main input header (10 pin connection that comes from the game board) you could have cold solder joints (this is what i had--they are not easy to spot so look very closely).  Also check your brightness and contrast pots wherever they happen to be--if you get a bad one it may look like the contrast is getting turned wide open.  you can wiggle the pots with power on and have an assistant tell you if its okay--DON'T TOUCH ANYTHING ELSE WHILE YOU ARE IN THERE THOUGH--VERY HIGH VOLTAGES ARE PRESENT!!!!

for the other 2 checks, you will need power off and discharge your monitor to be on the safe side (see the FAQ)