The board does not expect anything but connectors plugged in. Is this a total upgrade with a PS-3 Steam kit where you have changed harnesses? If so you might loose some engine functions depending on model. You also need to make sure you change the engine harness to match, or at least verify wiring including diodes for PV.
As John stated, the normal fix is just replacing board with a PS-32 or PS-2 3V with 5V connectors, plus the speaker. Instead of splicing into the harness red, why not add another red wire to the 7 pin for the tender pickup directly. More reliability/redundancy. G
