Paul for Model Number KitchenAid KHMS2056SBL2 Unit powers on but does not heat, or took a long time to get a glass of water to become "warm". I noticed the lights on the bottom of the unit flicker a bit while attempting the test. I assume its going to be a high-voltage-related issue, i.e., magnetron or inverter. I've opened the black housing to the inverter but don't see where to "drain" any lingering voltage out of it or a valid test. I don't feel comfortable testing the magnetron until I remove this board.
Answer Hello Paul. 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. Read More... Answered by AppliancePartsPros.com | Thursday, February 2, 2017