[ATTACH=JSON]{"data-align":"none","data-size":"full","data-attachmentid":3629483}[/ATTACH] Hi. I'm having same problem (stuck in protect) with Powermate 600 but none of tips above worked for me. After hours spent on it I've found that voltage on anode D5 is too high, around 8 volts instead of 2.5V. Also voltage on emitters of Q5 and Q4 is -9V instead of -11V. Pin 8 of I1 TL074CN is constantly on off state (+14V) rest of voltages near it match schematic. I'm convinced fault will be near I1 itself but everything tests ok. Any ideas?...