Chosen Solution
A year ago my GE microwave’s magnetron failed. I replaced it and it worked fine for a year and now I again have a short somewhere (loud hum then blows fuse). The magnetron resistances check out OK (<1ohm filament, no conduction to body), but then again, the old one that I had replaced also checked out OK this way, yet replacing it did fix the problem. Not seeing any arcing near the connector or at the antenna. The diode is fine (VF=9V, no cond. in reverse). The capacitor is fine (0.91uF, no shorts). Shorts in the transformer windings seem unlikely; I see no evidence of arcing or burning. Can’t be the door switch (the NC one), since if that was bad it would have blown the fuse immediately, not after a few seconds. So it must be the magnetron again, but before I buy another replacement, any ideas why they keep failing? Yanko
Hi, Is there any obvious visible damage to the magnetron itself e.g terminals blackened, cracked magnets, burnt antenna dome or any black heat marks on other parts close to it? Blackened connections could mean loose or badly crimped connections causing heat. The other problems may be due to overheating caused by microwaves reflected back to the magnetron . You don’t state the model but has it got a stirrer blade and is it working OK? Check the resistance of the magnetron with an Ohmmeter. Normal test is ∞ (infinity) i.e. infinite resistance or open circuit (OL) if you like. Any other reading means that it is faulty. If the magnetron tests OK then you may have to look for another reason why the fuse blows. Have you measured the resistance of the HV transformer?
