Weird problem with some resolutions (ie: Pac Man)

[RayB]

I built my MAME years ago but rarely use it.  I use a Vision Pro II horizontally, and I tweaked the size settings to a generally good setting so I can see both horizontal and vertical games fairly well.

I remember that a few vertical Midway games like Pac Man, Galaga, etc were quite tricky to get the vertical to "snap in" and stop scrolling, while also keeping other games fine. I had it working! Games like Pacman and Mspac had a little bit of over-scan, but in general I could see the score and the tops of the bottom bonus items (cherry, etc).

Last week, I had a BBQ and friends over and we had the MAME on. Now, all of those "picky" vertical Midway games display some "wrapping" at the bottom of the screen, and sometimes will vertically scroll. (By "wrapping" I mean that problem you often see on old monitors where visuals go off the screen and double back over. In this case it does this about half an inch from the edge of the monitor.)

I can go and select other games, including vertical games like TUtankham and they display perfectly. It's like this monitor has broken but only in one particular mode.


I use an ArcadeVGA card with a JPAC.

[SirPeale]

My guess?  It's been a few years since you got this working, and now that capacitors have had their values drift slightly due to age.  If you were running the original orientation it would probably still be okay, or just require a slight adjustment.  But since it was difficult to get there to begin with, its even more so now that the values have drifted.

Try this: turn it on to one of those games, and leave it on and see if it corrects.  If it does, there's your answer.  Might take a little while.  Keep an eye on it to see if it changes during that time (eg, the scrolling slows or whatnot).  Check every 15 minutes or so.

Have you tried adjusting it with the adjustment tools (knobs)?

[lilshawn]

(By "wrapping" I mean that problem you often see on old monitors where visuals go off the screen and double back over. In this case it does this about half an inch from the edge of the monitor.)

it's generally known around here as "foldover"

[RayB]

THanks Lilshawn, I new that term but forgot it.

Peale, no I didnt tweak controls (yet). The foldover worried me, so I didn't keep it on those games very long, in case maybe the signal range was damaging the monitor.