Microwave Oven Failures

I have repaired many microwaves. The diode (and fuse) are the weakest link and most likely to fail. Once replaced the microwave should last forever if you use an anti-static strap. I see them fail mostly with power surges, however after replacing them they never seem to fail again. This makes me think it is built in obsolescence, by the manufacturer not using proper anti-static procedures. It is also the cheapest part and easiest to replace.

The microwave should have its own dedicated power line, not shared with any other device.

Most electronic stores will carry the part, or do a part number search.

Other problems I have seen is damaged antennas, and bad belts, which are not related to the diode problem.

Many years ago we bought a (cheap) microwave oven in Belgium.

When I say one ... it was replaced four times before the fifth one did not blow.

The failures happened after anywhere between two weeks of use and the first time we started it.

The retailer was pretty upset, accused us of many things and had the mains tested, but no anomaly was found.

The "good one" lasted many years.

I believe that it is - just as you suggested - a lack of quality control or built-in obsolescence.

Do you live near beach where sea breeze come in? I had similar frequent failures with both LG and National brands. Had lot of trouble with agents trying to avoid guarantee. In fact one said the reason for failure is in HT circuit short circuiting due to salty air.\Same units worked in a place away from sea breeze perfectly for years after we relocated!

Your answer is intriguing. Yes we live slightly further from the beach but still within a couple of hundred yards, but are more exposed on the top floor now - so this could be a factor. In UK we are about 110 miles from the nearest beach.

duikerbok,

I would check the line voltage first, looking for either over or under voltage, either of which could take out the fuse or diode. I wouldn't expect both to fail from a steady over or under voltage though. The failure of both does point to some huge spike, Are you sharing the power transformer with some huge inductive load? If the microwaves are the only electrical failures, it is possible there is some metal or foil in a local product that you are microwaving.

LG_DAVE

Here is a great site for info about troubleshooting microwave ovens...

Be sure to to see the simple diagram for proper testing of the high voltage diode.

http://repairfaq.ece.drexel.edu/sam/micfaq.htm#mictstris

Nice going Skeeter, Drexel is my alma mater. Being a EE from there its nice to see something useful from Drexel that does not involve 2nd order Hankel functions. I printed it out. Thanks!

Where did you buy the microwaves? I'm asking because if they were built to operate at 110VAC, 60Hz, they may not operate at 50HZ current. Is that the frequency used in Spain? Are you using a step-down transformer from 220V?

I am under the impression that he comes from the UK, not the USA....Read his posts, he mentions UK....

Did I miss something or did you?

My assumption is: he lives in Spain, but travels to the UK, maybe on business.

The machine is 230v 50 Hz

There are big warning pages in the instruction book, but what cook looks there, about using the cooker when the oven cavity has moisture remaining from cooking, so presumably the manufacturer has found that this affects its functioning / or alternatively uses this excuse as a cop out.

Try using a surge protector once you have it repaired as suggested. Our local U. S. power company denies any surges on its lines, but light bulbs can get noticeably brighter and dimmer.

Thank you - will do. Sometimes we look down on the town and it's a wonderful show as different districts trip out and others come back on line - almost as good as the fiesta fireworks.

Thanks for your help, esp. for the detailed troubleshooting guides.

I found various sources of diodes and fuses in USA but who didn't seem to deal online, and eventually one in UK.

I contacted the UK Co. but the woman in sales was very sniffy and would not supply me.(what credit crunch?) However I got out of her the name of an Eastern fellow who had a repair business near me, and he was willing to get me the items. I took them back to Spain , put them in the machine, put the casing back properly and away it went like new but with a better fuse.