My Micro Wave ran hot one day and stopped operating completely. I replaced the blown ceramic fuse, now everything operates, except for heat, I have checked thermostats A25, A27, and A40 and all check okay. I cannot find thermostat A43. I am hoping that it is the defective component.. Can you possibly lead me in the right direction? Thank you for your time and cooperation.
Answer Hello George. You most likely have a "high voltage" side malfunction. Transformer, diode, magnetron, Capacitor. You will need to be extremely careful if you decide to test the components with a multi meter, Very high residual voltage is present, so make sure you remove power to the microwave and short across the terminals on the capacitor. The magnetron should have a reading of less than 1 ohm resistance across the two terminals, and an "open" circuit between each terminal and chassis ground. The diode/rectifier should have a resistance reading in one direction only, no resistance, or resistance in both directions indicate a faulty diode. The primary winding on the trans former should read approximately 450 Ohms resistance, the secondary winding should read 80 ohms resistance, and the filament transformer should read 100 ohms resistance. If all the readings are proper and in range, replace the magnetron.