Model #JMC9158BAS, this microwave sounded like it was working, but would not heat any food. After removing the wrapper, I started a cooking cycle and did a voltage check going into the high voltage transformer. Here I found 0vac across the two terminals which indicates there wasn't a complete electrical circuit to the magnetron. I traced the wiring back to the magnetron relay on the control board and did a voltage check on the two terminals. Here I found 120vac between the two terminals, whether the unit was running or not. Remembering that a relay will read just like a switch or fuse, this consistent voltage reading is an indication of the relay was not operating, but there was source voltage. After removing the board from the panel, I did a quick check of the solder joints and found a cold joint (it doesn't show up well on the photo) to the relay in question. Sometimes the relay will be damaged requiring the control board
to be replaced, but I was able to retouch the solder with my iron and it now works just fine.
« Last Edit: April 21, 2008, 10:20:08 PM by AJ »