Intermittent problem: sometimes the magnetron will keep running after the cook cycle. The interior light, fan, and...

Per jayeff's instructions, saying that the HV circuit (ie magnetron) only gets current if the Power Relay is activated, plus comments saying that relays can stick intermittently, I'll be assuming the Power Relay is on it's way out. Swapping out control boards to hopefully remedy this problem. Thanks @jayeff !

@lktrshn I also have a GE microwave doing the same thing: magnetron turns on when door closed, but fan/light/turntable stay off. During a normal cook, everything runs fine. Opening door is only way to stop the magnetron. Did just changing your switches resolve this for you?