I have a Street Fighter 2 with a DMD / DMD board issue which I have never seen before.

The issue is when I plug in the high voltage connector into my DMD display (NEVER with the game turned on), I instantly burn up D5 and D7 on the DMD board. If I leave it on for any length of time, it will blow the line fuse on the game.

Without the DMD plugged in, the game works fine. I’ve checked all the voltages going into the DMD board and all of the voltages at the DMD connector and I could not find any voltages that appeared to be abnormal.

It does not seem to be the DMD board that is the issue. I plugged 3 different boards into this game and all three burnt up when I turned the game on with the DMD plugged in.

I have also tried more than one DMD in the game.

At this point I do not know where to go from here.

EDIT - Problem solved. It was a short to ground on the high voltage line at the fuse holder on the transformer panel.

I have not done that, but the logic side of the DMD board should have no impact on the high voltage side of the DMD board.

I just tested the ribbon cable in another game. The cable is not the issue.

You can see the issue is always with the bridge on the -112V circuit.

Power Board-Circled (resized).jpg

This is not an issue with the board. Something external to it is causing some crazy voltage issues.

I have put the same exact board into another System 3 and it works perfect.

The output voltages (P2) to the DMD with the board in SF2 are:
1: 6.4 VDC
2: 62 VDC
4: 12 VDC
5: 123 VDC
7: -34 VDC
8: -17 VDC

With the same board in a different System 3 game, the output voltages at P2 are all correct per the schematic.