MVS/Supergun: Inconsistent RGB Output?

Greetings -

I have a homebuilt supergun housing a MVS 1-Slot
(older, large board) putting RGB picked directly
off the JAMMA connector to an ancient NEC MultiSync
monitor (MultiSync II, JC-1402HMA). I've also
tried using a different (older) NEC, JC-1401.

Different games will cause me to readjust the
monitor - for example, Magical Drop III makes me
crank up the brightness & contrast to max, whereas
Metal Slug X is perfectly happy at the mid-point
for those controls.

Is this an issue with my MVS board, or do I need
some sort of conditioning circuitry between the
JAMMA connector and the monitor? Both monitors
fire up & work fine with my DC's VGA output, so I
don't believe the monitors are physically
damaged - perhaps the NECs expect a smaller signal
(0.7V p-p?) and are being overdriven by some games?

Thanks in advance for any suggestions ...


Mike

Try putting some caps (forgot what value right now), or 75 ohm resistors. I found different things work on different monitors.

For what it's worth ...

I modded the RGB output today - 220uF caps
(electrolytic, so the 'positive' side faces the
signal source/JAMMA connector) in series with a
75 Ohm resistance on each of the R, G, and B signal
lines seem to have cleaned up the output
tremendously. Certain games (Magical Drop 3 for
one) seem to have inconsistent output within the
same game, but I'm chalking that up to the general
decreptitude of my MVS

Cheers,
Mike

Could be the voltages. I have the same in my cab. When my mvs is loaded with a 'large' cart that draws a lot of power, the brightness and colour intensity is a little lower. When i load it up with a 'small' cart like puzzle bobble, it's brighter and better

The same applies to when i change pcb's.. i have some bootlegs that seem to draw a lot of power from my psu, resulting in a smaller screen and dimmer colours. If i crank up the +5v a bit all is usually fine. But i suspect you are using a pc power supply

- Alex