Voltage Issue or Dying Monitor?

[SpongeFreak52]

Hey all, so here's my problem:

I've got a Wells Gardner 25K7197 in a cabinet I've been working on, with a VGA breakout cable connected to a standard PC VGA port. However, I've noticed that after about 30 minutes of the machine being on, there will be a somewhat loud buzzing noise coming from the monitor, and on the screen there will occasionally be white dots that appear here and there (obviously most noticeable on black backgrounds).

Now one thing I've taken into account is the fact that I am outputting straight from VGA to the monitor itself, meaning that it is likely only getting a 1v input, rather than the standard 4v. Would that be contributing towards this problem? I haven't tried powering the monitor alone, and as I'm currently out of town, won't be able to check on that for a while. Also, when the monitor was still connected to it's original X-Men JAMMA board, I didn't seem to notice these problems, although it could simply be coincidence.

Thanks in advance, everyone.

[grantspain]

its not the marquee light is it?
that will give a similar affect to your description
otherwise if it is monitor related it could be bad solder joints considering it seems to be heat/time related

[boardjunkie]

You definitely need a video amp to get the .7vac color signals up to 4-5v to get correct color/brightness. But....there is an unstuffed connector on the 7000 board that will accept a .7vac video input.

http://arcarc.xmission.com/PDF_Monitors/Wells%20Gardner%2025K7191.pdf

Its P7 at the top left. You'd need to feed the sync signals into the regular vid input header at the R side of the board.

http://pdf1.alldatasheet.com/datasheet-pdf/view/108910/NEC/UPC1397C.html

There's the datasheet on the 1397 video processor chip. Pin 9 may need to be tied HI (its currently tied LO via a 1K to gnd) for those inputs to be enabled. I've not had to do this as of yet so I can't give any further details on the hows/whys.

As far as the noise, check for cracked solder on the board. Resolder the flyback and horiz width coil *first* even if it looks ok. The width coil will burn a hole in the board if connections become intermittant because of cracked solder. Video input and yoke connectors should be resoldered as well. Just give it a good going over. Fresh electrolytic caps may be in order if it still has the originals.