Monitor Brightness Fluctuations....Help !!

[smithers]

Hoping someone can help me, as I've posted on Killercabs and no one seems to know the answer.

I have an LS29 candy cabinet, which is only about a year old.
I have installed a pc with Mame and arcadevga and a j-pac.
Got everything working great except for 1 thing.....

Everytime I use the machine, whether on windows or an emulator, the brighness continuosly changes !

Even scrolling up and down a wep page, you can see the background changing colour.

It seems conected with what other colours are on screen at the same time, as in Sonic, the sky is light blue and the floor light green....as soon as you hit a ramp and go skywards, as the sky goes adark blue, maybe because there is no green on the screen to compensate.

There are a few other people on the killercabs forum with exactly the same set up getting the same problems as me, but it seems that pcb's run perfectly. so it much be the pc setup.

Could it be something to do with the power supplys or the voltage. I have left my cab power supply in to power the marquee etc..might that cause this ??


Please help me if you have any ideas at all..

Thanks in advance,
Mark

[pcb]

Sounds like cold solder joints to me.

Best,

 - Mike -

[smithers]

Sorry - no idea what that means...could you clarify ?

Thanks  Mark

[dabone]

Email Andy at ultimarc and ask if a bad video amp on the jpac could cause this.

Later,
dabone

[AndyWarne]

There are several possibilities but the most likely would be a DC voltage building up between the J-PAC and the monitor, which in turn would be caused by either a monitor fault or a grounding problem. Make sure the monitor video ground is connected. Also make sure monitor chassis is grounded, and the PC case.
Andy

[smithers]

Thanks for the advice Andy.

To ground my monitor chassis and pc case, is it simply a case of attaching a wire to somewhere on the metal  and running it to a ground on the jamma harness ? or is there more to it than that.

I'm fairly new to this, so any specifics would be much appreciated.

Mark.

[smithers]

Thanks for the advice Andy,

To ground the pc case and the monitor chassis do I just run a wire from the metal to one of the grounds on the jamma harness or is there more to it than that ?

I'm new to all this so any specifics would be much appreciated.

Thanks,
Mark