microwave oven stopping prematurely, repairable?

is the cooling fan running?

tes

Thanks Mike. And yes, cooling fan next to the power supply runs. I hear humming noise of the microwave coming on, so my guess every moving part is working...

-Tin

It appears that "something" is overheating that causes the klystron to lose power, and this "something" gets warmer with higher power settings. If that "something" is not a component /intended/ to shut off the unit when it overheats, you'll probably have a hard time finding it.

Freeze-spray might locate it. Otherwise, I vote for buying a new unit.

Sounds slightly similar. Had a GE unit that started making an internal arc sound [the arc burnt around the waveguide entrance to the microwave chamber out of sight. Without total disassembly could not see it].

Symptom sounds similar, uWave would run, then [in my case] hear arcing sounds, and then shutdown. Arcing did NOT occur if a glass of water were present. But arcing occurred if I was trying to toast something dry, like bread. My guess was that the damped microwave chamber keeps the voltage down enough there is no arcing. And when the chamber is unloaded, the resonant voltages get high enough to enccourage the arcing. Culmination of this was that after 'limping' along for 4 months, the burn spots in the waveguide feed required replacing the unit, had to buy a new one.

If you're OK with tools, and can discharge the capacitor safely, consider disassembling the oven and cleaning it.

An insect getting carbonized in the HV section could be the only problem here, and you gotta scrub the carbon track away to fix that.

I have an older MW oven that wouldn't shut down for any irregularity. One day it started sparking and had a smell, just like you said. Upon closer investigation I found that the mica plate in front of the wave guide had deteriorated and had a dark spot that arced under power.

I took the mica off and ran the device, and it worked just fine. I ordered a sheet of mica on ebay to cut to size cause I couldn't get the original. Before that arrived I found a MW Oven on the road side for verge collection and removed the mica from there. I trimmed it a little and fitted it in my oven. No problems ever since. Got a spare one now in the junk box:)

Looks like the mica sheets can get damaged and take up moisture, which sort of shorts out the micro wave energy. Don't know if this happened to your machine but it wouldn't hurt to check.

Tony

Excerpt from the faq: More on the waveguide cover and cleaning That cover is made of an insulator transparent to microwaves, usually mica, not a metal. The material can be obtained from places like MCM Electronics which you then cut to size with a pair of scissors or a paper cutter.

First, completely clean below, above, inside, and whatever of the cover material is remaining. All traces of carbon and burnt on food must be removed. In particular, you need to clean inside the waveguide above the inside top of the oven as well.

Then run the oven (with the waveguide cover removed, if necessary) to verify that there are no other problems (there probably are none).

Sometimes, you need to remove the outside metal cover in order to remove the waveguide cover. There may be little plastic pins or snaps which tend to get gummed up with burnt food and may be difficult to pry off from inside the oven. If you do need to remove the metal cover, jot down the locations of each of the screws (they are not always all alike) and stay away from everything but the waveguide cover itself (especially the high voltage components!).

That waveguide cover is not essential to the operation of the oven but it does prevent food from entering the waveguide and getting trapped there.

Thanks for everyones reply! Bugs inside the microwave seems unthinkable but is probably the problem. Are they trying to eat the HV wiring or something? :) I will try to disassemble the microwave and see if I can air spray out any foreign material, but I am not trained to deal with all that high voltage stuff and so would stay away from it...

Much thanks again. Tin