Pro Monaco GP board repair help (video synch)

[nilfisk]

Hi,

I have tried to get my prev. working Pro Monaco GP up and running again, and am stuck with a video sync problem. Other than that, the machine is working again, and I can see all the graphics etc. when playing, its just that the screen keeps rolling. I have replaced most of the components that form the sync circuit on the video pcb, but with no success. As I won't get any further with my shotgun approach now, I am looking for someone who's willing to take a look at the board; I am pretty sure it's fixable with the right equipment and a bit more experience on these pre-CPU beasts.

I have a working video pcb from a Monaco GP (sans "Pro") as a reference, which is pin compatible and uses the same circuits, except for a few re-arranged ICs (I even have these documented by now, e.g. "IC 92 on Pro is IC 101 on the regular board")

Thanks,

Martin

PS.: The board has its own crystal and puts out video indipendently of the other Monaco boards, so it's rather easy to wire it up for testing / troubleshooting - just provide +5v, ground, and wire up the video outputs.

[DarthNuno]

when playing, its just that the screen keeps rolling.

It's more a monitor problem. Did you try to turn the sync potentiometer? That monitor would also require a capkit.

[nilfisk]

Hi,

Unfortunately, it is not. I have verified the monitor with the known good video pcb, and am currently working on the pcb on my testbench, where I use a known good CGA/VGA converter. It definitely is a problem with the onboard sync circuit.

Thanks though for trying to help.

Martin

Update: please see http://www.ukvac.com/forum/topic331476_post773295.html for updates if you're interested, as I am currently discussing further steps there.