Because the supply is unregulated, it is normal for the voltage to drop as the current load is increased due to resistive losses through the bridge rectifier and increased rate of discharge from the holding capacitor.

However, 11.3V seems low. A normal stock game powering the optos will be over 13V. Addition of the ColorDMD generally drops the voltage by around 0.5V. I'm not sure about the drop pulled by Pinsound, but you can unplug Pinsound and check the readings with J116-119 plugged in, with/without the ColorDMD.

If the voltage is lower than 12.5 V with Pinsound unplugged, you may have a failing unregulated 12V power supply. Could be a failing bridge, cap, cold solder joint, or failing trace on the power driver board.

To see if it's the supply, you can try swapping the power driver board with one from another WPC game and recheck the voltages.

Voltage drop is very significant when the motors start pulling current. That's a good sign of a failing supply.

It's unlikely there are any problems under the playfield. I'd swap driver boards to see if voltages look better.

If so, next step would be to check traces and reflow any cold solder joints on the unregulated supply. Then if still not resolved, swap out the cap and/or bridge.

Great! Glad I could help.

Thanks for the update.