There are a couple of construction details mentioned in the assembly manual that need repeating here.
1. The main PCB transistor Q2 must be installed with its large flat face oriented toward the RIGHT side of the board. The PCB silk screen is INCORRECT. There are pictures posted that show the transistor installed in the opposite way, these are incorrect.
2. The installation of the heat sink on Q11 is critical. The hardware stackup should be screw, passing through flat washer, back of heat sink, black heat sink pad, back of transistor, lock washer, and nut. The three legs on the heat sink should be snipped off. Before soldering the transistor to the board, check the spacing between the heat sink and the board to make certain that the sink does not contact any of the surface mount components on the board. Readjust the sink on the transistor if necessary. Only then should you solder the transistor down. Finally, be certain that there is no contact between Q11 and Q12 before power up.
There have been pictures posted that show an incorrect hardware assembly.
If the incorrect assembly is used, it is possible for the screw to contact the tab of Q12. If this happens during power-on, the circuit will be damaged, and somebody will have a bad day.
73 Dave NM0S