Quoted from FatPanda:Testing with the machine on, pin 10 grounded, DMM in DCV, J5 unplugged.
R29 top leg 5.17V
Bottom leg .78 VCR12 non-banded side .796V
Banded side 18.4 mV
Cheers, these readings say you have a short circuit at the Q12 transistor - likely Q12 itself. Specifically between the transistors "Base" leg and the "Emitter" leg. This short is stopping the Q12 transistor from actually switching on.
--- Remove the ground jumper from pin 10 of U3. Now what voltage do you measure at the non-banded side of diode CR12? Should be around 0.3 volts.
--- Can you post the part number on the Q12 transistor, just in case it's the wrong part.
--- Post a picture of the back of the board around Q12 in case our eagle eyes spot an accidental solder short.