Question about LG LRM1250 Microwave Oven

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Oven won't heat even though each component seems to be functional.

I have an LG LRM1250 that won't heat. I have 115VAC to the primary of the transformer and 3-4VAC across the filament taps. Resistance is less than 0.1 ohm across the magnetron terminals and infinity from each terminal to ground. HV transformer tap to ground is ~90 ohm. Diode is ~50Kohm/infinity. Resistance between each capacitor terminal and the case is infinity. The ohm meter deflects then returns to infinity as I switch the leads back and forth across the capacitor terminals. Energizing the transformer while the magnetron is disconnected results in the capacitor holding a charge.
The oven is only two years old and the cooking power never decreased before it just stopped heating. I suspect the magnetron, but it appears to test ok and it appears to be in good physical condition. Anyone have any ideas?

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  • plastic Jul 19, 2008

    Thank you for your 99% certainty and your concern for my safety. Rest assured I am experienced with HV AC/DC. I think the possibility that the magnetron is the problem is high enough for me to try a new magnatron, and is certainly high enough for me to give you a FIXYA! Thanks.

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Even though the magnetron passed the continuity tests, it can still be bad. In fact, most of them fail in ways that do not show up in continuity tests.

And I am 99% certain yours is bad, especially since you have proven that the filament voltage and high voltage DC is being produced and sent to the magnetron.

I must say that the testing you have done is not recommended for people without plenty of experience, but apparently you did it safely. Please don't press your luck, since the high voltage can be instantly lethal.

For Goldstar / LG / L.G. parts, call 1-800-243-0000 (M-F, 7am-8pm CT, Sat 8-5 CT) and choose the appropriate prompt from the menu or visit here.

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

Posted on Jul 18, 2008

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