Greetings!

I'm working on fixing the microwave on my GE JKP90 microwave/oven combo. It develops a strong odor of burning insulation within seconds of operating - yet it is working.

When I opened it up, I noticed that the black lead that connects to the primary winding of the transformer was brittle and crisped - it seems that this is the source of the odor. That made me think that the transformer was drawing too much current to make the black primary lead burn up close to the transformer. I assumed that the transformer itself was bad - there is what looks like a burned area on the secondary coil of the transformer, so I thought that the secondary of the transformer had shorted out.

The measured primary resistance is 0.6 ohms (test table says it should be between 0.2-0.4 ohms), the secondary is 113.5 ohms (measured to ground - test table says it should be between 60-90 ohms), and the filament resistance is 0.4 ohms (test table says it should be less than 1 ohm). The primary and filament windings show infinite resistance to ground.

So, with the resistance measures for the primary and secondary being outside of the ranges listed by the test table, I ordered a replacement transformer. After installing the new transformer, the symptoms are still the same...the microwave operates correctly, heats water as expected, but develops the burning odor within seconds of operating.

Has anyone seen something like this before?

Any ideas on how to proceed are most appreciated!

Thanks - Joe