tech : Asteroids jagged vectors pcb prob

hi all..

I have an asteroids here that is bugging the hell out of me. It has to be a
pcb related problem, although it was in part exagerated by a monitor too. I
have a very early production asteroids with many early features, one of
which is the g05-801 monitor.

http://www.andys-arcade.net/Dcp07480.jpg

the pcb looks fine in my test rig on my scope screen, does not display the
same type of problems, however in another asteroids machine (G05-802) the
screen is no where near as bad, but has little loop jumps over the
intersection of the vectors on the crosshatch in test mode.

So the 801 doesn't like this pcb very much at all, the 802 doesn't mind it
that much, but its still not perfect.

from the distortion of moving objects, it looks like the rocks are passing
over a very uniformed grid. The spikes are stable and do not move or ripple
by the way.

I was initially thinking caps on the monitor, but i seem to remember someone
having similar probs and thought i'd post here, mid-fixing.

FYI i have a ground cable hooking the frame, pcb and psu together already.

i will replace caps on the pcb tomorrow, but for now, anyone seen this
before and can pinpoint it right away? :)

thanks.

Andy Welburn
www.andys-arcade.com

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Received on Wed Feb 26 15:29:37 2003