Joe for Model Number jvm 1750sp1ss Microwave won't heat. Door switches are ok. There are two thermal fuses. The one on the right is ok. The one one the left KSD 40 LC 70 thermal fuse has no continuity when I test it. Is this part bad? The third fuse an automotive fuse is ok. Joe,
Answer Hello Joe. 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 transformer should read approximately 450 Ohms resistance, the secondary winding should read 80 ohms resistance, and the filament transformer should read 100 ohms resistance. All of these are +- 10%. If all the readings are proper and in range, replace the magnetron. Read More... Answered by AppliancePartsPros.com | Tuesday, November 24, 2015