The Virtual Repairman's Appliance Help

K Shanks · Apprentice DIYer Joined: 20 Jan 2010 Posts: 1

I have a LG microwave model LMVM1945SB. We had a leak in the roof that when it would rain really hard water would show up inside the stirrer cover. This has happened several times before I was able to replace the roof. The microwave continued to work even though getting wet. However it now seems to work at about half power. This did not seem to happen all at once more a gradual change. Approximately 5 minutes to cook a bag of popcorn and it typically will only be half popped at that. It also seems to have hot spots. I checked the stirrer and it rotates when running. I have now taken it down and removed the cover to look for any obvious burns or corroded terminals. I have not found anything. If you have any ideas or things I could test I would appreciate it.

Virtual Repairman · Posted: Wed Jan 20, 2010 6:14 pm Post subject: micro problem

Low power could mean any part on the High Voltage circuit has failed, such as the magnetron, diode and HV capacitor. Hot spots in the cooking pattern are definitely stirrer-relatd as well. A bad stirrer can cause failure of all of the parts in the HV system due to overheating and RF feedback to the mag tube. I usually start out by examining the mag tube visually for signs of sagging cooling fins (overheating) and any resistance value of more than .1 OHm in the Mag tube when checked with a good OHM meter. Diodes and capcitors have their own may of being checked, so if you are electrically-challenged, you can bone up on the instructional guides in the Repair Manuals Forum. For instance the guide on "How to Use Test Instruments" may give you a lot of good pointers.

Frankly, this unit may or may not be worth sinking a lot of money into. Anything electronic which has has water penetration is doomed sooner or later.
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