I have a DMC-1 Door operator with a FX3 door board. The 2amp fuse is blown on it. I replaced it with a new FX3 and changed the chips over and it is doing the same issue. The fuse blows soon as the p150 and g150 are connected to the board I have all other connectors unhooked and the motor/cap wires removed from the board. The P150 and G150 connectors have 151 VDC across them when I remove them from the board. They have 108 VDC across them when I connect them to the board. The voltage is the right orientation also. I'm not sure what could be causing it. I sat the board onto cardboard to eliminate the chance anything was shorting and connected them and the fuse still blows. Should I get a third board?

The rectifier on the relay board in the controller supplying the 150dv is probably bad.

Put a 100-150 ohm resistor across the p150-g150 wires going to the board, but not attached to the board. If the voltage drops off to 108vdc, look off the board for a load or cross connection changing the characteristics of the 150vdc. If the voltage doesn't drop, then the problem is still on the board. Wattage of the resistor should be at least 200w. A door resistor should be fine.

Did you ever find a fix for this? Having the same issue, with fuse blowing on door board, I have 163V across p150 and g150.