with the power off and ideally the board out of the machine, test with a meter Q81 (TIP122/TIP102) against the transistors either side on the board and you should notice a difference, also set you meter to continuity and touch the metal tab of Q81 with one probe and ground with the other, if you get zero ohms an/or hear a tone/beep the transistor has shorted internally, the other option it has opened internally.

also check the pre driver transistor 52 (2N5060), it may have also died. If you find Q81 faulty is a good plan to replace the pre driver also.

if you decide to just replace these and the fault still exists, the next component to check/replace is U55 IC7406.

sorry for misleading you with transistor & pre driver numbers, I assumed you had an original board, now I see a rottendog and reckon they use MOSFETS.

a faulty MOSFET could change the value of the resistor. Like the resistor may be okay but the MOSFET's internals possibly being damaged will give you a different reading of the resistor. Best to lift a leg of the resistor to be sure.

but hoping for you it's a simple fix.