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LG microwave repair

Let me start out by saying I am not an electronics tech but do understand basic electronics and schematics and have read the s.e.r. microwave faq and understand the precautions about working on high voltage equipment and discharging same. Anyway my problem is my LG over the range microhood. Got is from a liquidator about a year ago so is not under warranty and from the near thestart there was the occasional arcing sound which recently got quite frequent and now it does not heat at all.(or arc). I pulled the covers and made sure the capacitor was discharged and took a few measurments and the leads to the magnetron read about 0.8 ohms which seems ok according to the faq but the diode from the capacitor to ground reads open both directions so I suspect that is the culprit. The problem is the intermittent arcing from the start which if I replace the diode will most likely return and in fact the wave tunnel where the magnatron is attache to has the paint scorched off of it for about 2" area above where the magnetron attaches below. I believe it said something in the faq about touching up the paint for arcing problems but did not say what kind of paint to use.

So my questions are should I get a replacement diode and remove the magnetron and clean up the wave tunnel and repaint it and if so with what kind of paint or does this indicate a problem with the magnetron as well?

If not is it worth putting it back together and taking it in for repair? A new one like this will run about $275 buck here.

Reply to
John Wayne
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From my experience working with microwave ovens, the diode you speak of needs a much larger forwarding bias voltage before it conducts. Therefore, a regular multimeter will show it as open. Take a look at this thread from a few years back:

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David Farber
David Farber's Service Center
L.A., CA
Reply to
David Farber

Arcing would presumably be caused by exposed sharp edges in the waveguide or oven cavity.

I'm not sure what the "correct" paint would be, but it would definitely be something non-conductive. I would start by cleaning up and repainting the scorched area.

If you disconnect the oven light, you should be able to see where the arcing is occurring. Remember that excess exposure to microwaves will coagulate the proteins in your eye, leading to cataracts or blindness. Be careful.

Reply to
William Sommerwerck

Paint is for cosmetic purposes and to prevent rust. It won't affect the arcing. Most non-toxic enamels will be fine, but test in an inconspicuous area first and let it dry overnight at least.

He will need to check the diode with a voltage greater than 6 V to see if it conducts in one direction only.

0.8 ohms - if accurate - seems way too high for the magnetron filament. It should read essentially 0 ohms on a common DMM.

It's possible that the arcing has been due to contamination inside the waveguide all along, and not anything faulty.

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Reply to
Sam Goldwasser

The 'diode' is a highvoltage stack, so it might normally read open (depends on your meter); it's possible to test it with a couple of

9V batteries in series with a 10k ohm limit resistor, looking at the voltage drop on the diode when excited with 18V.

If there was arcing, you might suspect the interlock switches, and look for signs of loose connections. The most likely cause of 'complete failure' is still the fuse. Diode failures are usually not accompanied by any noises. Interlock switches with a speck of dust in the contacts ARE noisy.

Reply to
whit3rd

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