Thursday, December 29, 2011

Microwave magnetron replacement

Important note: microwave oven contains very high voltage and should be handled with extreme care.

Our GE Spacemaker microwave broke (again). This time it was the magnetron. One of the isolators on the filament connector burned out and the current started flowing between the connector and the magnetron body. This was accompanied with loud noise and sparks.

Turned out that the magnetron has very long warranty - 10 years. If your magnetron goes, contact your microwave manufacturer before buying a new part. Few days later I received a new magnetron.
The microwave repair FAQ states that the high voltage diode must be replaced together with the magnetron. I found this to be true because as soon as I turned on the oven after magnetron replacement the old diode went up in smoke.

Replacement diode from the manufacturer was priced astronomically high. In my opinion $50 for a $2 part is a bit overpriced. I started looking for suitable replacement. As it turned out most household microwaves use diodes with the current from 0.3A to 0.5A. Our GE Spacemaker had diode with the current of 0.35A and voltage of 12kV. Most of the places that sell microwave parts do not specify any parameters on the parts that they sell. On ebay however one can find diodes with the stated parameters but most of them ship out of China and have shipping time of several weeks. I was able to find one person selling NTE517 diode for a reasonable price. This diode should be able to replace HV diode in pretty much any household microwave. It has Vpk-15kV and Io-550mA. The person was selling two versions of the diode, one without mounted connectors and one with connectors. I found one without connectors first so I bought this one. If you have problem with soldering or just want to save some time the one with connectors is a good choice just for a few $$ more. I cut connectors off the old one and soldered them to the new one. Original connectors are crimped to the leads but soldering them is OK too. After that I used heat shrink tubing to isolate one connector. Original diode was isolated with medium thickness tubing which should be good up to 20kV. I could not find that type of tubing so I used just a regular tubing and that seems to work just as well. It probably will not hold if the diode is touched while under voltage, but I do not have suicidal tendencies and have no plans of touching it.

The lessons from owning and fixing the GE microwave are following:

* GE microwaves are poorly designed and poorly made. For the appliance that is built in to the cabinets they sure break a lot. Our microwave is cracked in several places, some that are not even touched.

* GE charges way too much for parts although they ship promptly.

* NTE517 is a good replacement diode for most of the household microwaves.

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