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Arcade Collecting => Miscellaneous Arcade Talk => Topic started by: Crowquill on August 04, 2007, 03:29:06 am

Title: Jamma in a Neo-Geo MVS cabinet
Post by: Crowquill on August 04, 2007, 03:29:06 am
The Neo-Geo MVS cabinets (2,4,and 6-slot) use a pinout very similar to the JAMMA pinouts. I've read before that running a MVS board in a JAMMA wired cabinet can overload the amp and burn it out. Would the same be true for the reverse (JAMMA in a MVS cab)?

I modified the wiring diagram from HardMVS to highlight the differences.

Although not indicated, in my MVS cab the ground from the left and right speakers connects to pin e or 27 (can't remember which). If connected to JAMMA, the MVS board is trying to output both left and right to the same speaker making a circuit. No wonder it overloads the amp.

Is there a big difference between wiring to the "speaker negative" pin and running it to a Ground pin on the harness? Audio is not my strong point.

I guess I could somehow rig up a DPDT switch to make it switchable if it is harmful.

The audio connections are the only ones that seem to be a problem:

E/5 - No connection
M - as long as the switch isn't pressed there's no connection
S/15 - No MVS cab even had coin slots 3-4, so no connection
d/26 - No connection
Title: Re: Jamma in a Neo-Geo MVS cabinet
Post by: MonMotha on August 04, 2007, 04:14:44 am
Due to the design of many audio amps, you CANNOT tie the "speaker negative" line to power ground.  Doing so will cause various problems depending on the amp topology, but most common single-supply topologies (which is most of what you'll find on JAMMA boards) cannot handle that.
Title: Re: Jamma in a Neo-Geo MVS cabinet
Post by: Crowquill on August 07, 2007, 12:58:29 am
That's pretty much what I expected. I guess the MVS amp is just built to work that way.

It just sucks since the WG K7100 monitor in my MVS cab will sync to any game I've thrown at it. Can't say the same for the Neotec N2515 in my JAMMA cab.

Thanks for the input!