Mame distortion

[Goz]

I've just got a Jamma conversion cab up and running. Will post pics after i complete refinishing the exterior.

I'm having the following problem in MAME and hope that someone can smack me on the forehead and say "bonehead, you need to change this setting". I'm hoping it's this easy, but have not seen anything document like this one.

Problem: When playing a game such as MetalSlug (happens in alot of games) when a large explosion or effect occurs, the screen scrambles for just a second and then returns to normal.

Here's the rundown on the setup.

Mame .78 windows command line
Arcade VGA set to 640 x 480 x 16bit color
J-PAC set to 15kHZ happend as well with the additional jumper on for 31kHZ
front end is MAMEWAH, but happens if I launch a game separately using MAME32 as well.
WG monitor.

VHOLD has been adjusted and the MAME.INI config is set for 640 x 480 not auto.

Any ideas?

-Goz

[Howard_Casto]

Vhold?  Don't you mean resolution?

[Goz]

No I meant VHOLD. As some know i had a problem for a bit where VHOLD would not stay as set.

Sorry was typing the message in  a hurry, they should have been on separate lines in the post  (VHOLD and the resolution setting)

I have tried various resolutions however 640 x 288 and a few others, unfortunately the problem re-ocurrs

-Goz

[GamingGreg]

This sounds like a VHold problem in the monitor (really sensitve or something).  Did you adjust the VHold to find a sweet spot between resolutions like 640x480, 640x288, and 320 x 240?  

I'm using an old WG arcade monitor and I could never find a good spot between 480 and 288 lines of resolution.   I ended up using the AVGARES util with a config that includes modes of only 480 or 240 lines.  This solved my problem where some games couldn't be seen, because the VHold "wigged out" in those modes.  There's a config on this page here that might be of some help to you.

[Goz]

Tried AVGARES with that config. Unfortunately it made no difference. The control board thing-a-ma-bob (technical term) that has the pots for vhold, hpos,etc for the monitor looks like it is in pretty bad shape. If I can figure out the correct name for it, I may end up replacing it.

The Jamma game that's also in the cab (Police Trainer) works flawlessly. Without the berzerk screen anomoly.

-Goz

[Howard_Casto]

This is just a guess, but it sounds like you need a cap kit.  Probably if your pots are in bad shape then your transistors and resistors and those highly technical thing-a-ma-bobs are failing as well.

[Minwah]

Perhaps try cleaning the pots with electrical component cleaner (RadioShack)...