Question about GE XL1800 1100 Watts Microwave Oven

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Reversed polarity a problem?

We just realized the polarity of the outlet that feeds our microwave was reversed. Can anyone hypothesize on whether this could be leading to HV problems? The MW produces a loud humming/buzzing, no heat. The dome on top of the magnetron shows some charring. Have replaced magnetron once already.

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Re: Reversed polarity a problem?

The polarity won't matter to the normal functioning, but to ensure safety in case of a short, it should DEFINITELY be corrected.

You probably have a bad magnetron (again) and possibly a bad high voltage rectifier diode too.

GE had a campaign (but not a recall, mind you!) covering several models.

Details are in their bulletin at

The parts kit (that GE used to pay for) is part # WB27X10489 and is shown in the photo below.

If you or a friend decide to look into it, we have critical information on safety, disassembly and door switches at our site, and our link is at our listing here on FixYa:

You can find helpful exploded view diagrams and order parts by entering your full model number here:

Chances are GE won;t cover any of this, but just in case you want to contact them, GE Customer Service is at

We're happy to help and we appreciate your thoughtful rating of our answer.


Posted on Jan 20, 2008

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Your high voltage power diode has most likely failed. That or the magnetron itself has failed where as the oscillator is stuck. My bet is the power diode is what has failed.

First off short out the capacitor AFTER removing the outer chassis with a screwdriver. Hold the screwdriver back on the handle and short across the 2 capacitor terminals. Locate the power diode that will be the wire that is metal. Remove it from the capacitor. Use a meter and read continuity of the diode. Reverse the test leads and read continuity again. In one polarity it is supposed to read like a wire (ZERO Ohms) and in reversed polarity it is supposed to read infinity. (Open) If you get open or short in both directions it has failed.
Diode PN is:

You can change this part and still have a problem with the magnetron... usually though a diode change brings them back to life.

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For post reference use this parts diagram:

Usually either the capacitor (Item 20 above) or the diode (item 19 above) causes this problem.

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These are the 2 most common reasons for the unit to run but not heat. If after testing you still have no isiolated the problem, respond with your results and we can proceed from there.

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F7 is q Power to magnetron

1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Unplug microwave oven or disconnect power.
4. Check cooling fan operation
5. Check resistance of the magnetron thermostat.
6. Check the magnetron.
7. Check P2, P4 and P27 connections.
8. Check wiring to the 1100W inverters and control system. See
“Checking Inverters.”
9. Check operation of all interlock switches.
10. Replace inverter, if defective.
11. Replace all parts and panels before operating.
12. Plug in microwave oven or reconnect power.
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14. Replace electronic control.
15. Replace all parts and panels before operating.
16. Plug in microwave oven or reconnect power.
17. If problem persists, unplug microwave oven or disconnect power.
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