Help - MV-1F has no video sync?

I've got a Neo Geo 1-slot (MV-1F) I picked up off of ebay that I'm trying to repair. The previous owner did something screwy with the video, as the video ground line was crisped.

Anyhow, after repairing the video ground, when I boot it up, it looks like I'm getting the test grid on screen, but the board is not putting out any video sync (at least, none that my logic probe can detect). I'm getting signals on the other video lines, just no sync.

It's a 3-layer board, so it's hard to trace the circuit manually. Does anyone know where I can get a copy of the Neo Geo schematics? I've looked at all the usual places, as well as at a bunch of NeoGeo places on the net, but I just can't find any. Failing that, if someone can describe which chips are responsible for generating the vsync, I'd be much obliged.

Thanks for any help,

-druid

Try Briggs site <a href="http://www.hardmvs.com" target="_blank">www.hardmvs.com</a>

Make sure all your dip switches are in the off position also

Ask Nightmare Tony, he's a former SNK tech...

I'll check the dipswitches, thanks. Although I don't expect it'll change the video sync.

I talked to Briggs at the hardmvs site - unfortunately, he has no schematics, just the service manuals which don't give much hardware-level info.

I'll try Nightmare Tony - thanks.

-druid

Just to follow up - I never did find any schematics. However, I traced the circuit manually with my logic probe, and found that the 100 ohm resistor in the vsync circuit was nearly open (it read something like 700k ohms). Replacing this resistor restored vsync and now I have a working PCB!

-druid

Hey glad to hear you got it fixed !

"GAME ON !!!!!! "
[Waynes World }

Kewl on getting it fixed. Sorry I've been so away, so darned busy these days. lost my job a month ago and at least working comfortably doing again what I love best, repairing arcade games. buying a house and land, and putting out a music CD as well. If I remember, the 100 ohm is hte pullup, with a 47 ohm series. Glad it didnt crisp anything else. Call it faulty memory, the sync *MAY* emenate from the Neo-F0 chip, whihc acts as the clocking for everything in sight.

err, you won't find schematics. They don't exist!

Well, may still be some somewhere - whoever took over that side of SNK, but these things often go missing at times like these. We were lucky to salvage the atari ones.... although those machines had service manuals available.