I have a Laser Cue project that I recently installed an aftermarket driver/mpu board and power supply. The power supply is made by Gulf Pinball. When it was originally installed, the game would boot up but would randomly reset at times. Now it does not boot up at all. If I have everything plugging into the power supply, I hardly get anything at the 5V test point. But when I disconnect J6, I get 5V at the test point as well as the pins on J6 (I think it is pins 8-10). Once I connect J6, I lose the 5V. Everything else seems to be working ok. I am getting 10V AC out of two wires...J1-10 and J1-11 (for a combined 20V that gets converted to DC on the board). Fuses on board are all fine.

What would cause the power supply to have proper 5V except when a specific plug is plugged into the board?

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I narrowed it down to the Rottendog board. I remember coming across another post where one of the metal mount tabs was touching the backside of the board where there was a trace. So I put some electrical tape on the tabs and it fired right up! Thanks everyone for the help. Now I need to figure out why one of the drops is not resetting.