I would start by testing/replacing the electrolytic caps on the power supply board as this is the cheapest solution, the most common problem, and you have already measured an unexpected voltage on this board. Here is a picture with red arrows pointing to all the electolytics on your power supply board:
[image|1535894]
Look for any capacitors that are bulging, or even leaking, from the top vent. You can test the caps with an ESR meter to confirm a fault, but isn’t necessary if you don’t have one.
WARNING: Be sure to discharge all caps before messing with them!!! [guide|75901]
After this, look to replace the power supply board.