Microwave oven catches fire. Repairable?

On a number of occasions I've simply removed the mica or plastic "window" and discarded it, but this makes it possible for food splatter to enter the waveguide - in extreme cases this can damage the transformer or rectifier!

if the microwave oven is out of warranty, it would be safest to discard the unit, and replace it with a new one.

In the case where there is a seriuos short causing an actual fire, the manufactures would normaly replace the unit during the warranty period.

If it was a simple failure where there was no fire or hazard condition, the defective parts would be changed, the unit would be tested for performance and safety, and then returned to the customer.

Jerry Greenberg

Well the microwave is otherwise junk, so may as well remove that cover and see if it fixes it.

Yesterday I was browsing a household goods store and saw a microwave+grill for £29.99p - no-ones going to go to all that trouble on such a tiny margin.

probably the rf arc went across a migrating cricket or other bug that used the area for heat. or it could have been just some buildup of food debris that gets carried along with the air/moisture movement inside the oven..

("its like a self cleaning" oven) he he he!

but, if it still works, just keep using until it burns your home down. ;-)

I dunno guys . . . I have a Whirlpool 1200 watt and my wife a Panasonic 1,000 watt oven. We have both had the same experience. For no apparent reason the window on the wave guide spits sparks smokes gets noisy and makes lots of light. Wife panics, and I jump over furniture to get to the oven and shut it down. Hers has only lit up once mine twice. I cleaned mine she cleaned hers - the black spot (on mine the size of a quarter) is still there and has been working that way for two years now.

Now the butter in the oven thing - I've noticed the same sort of anomaly (it didn't cause the window to light - so that may be coincidental) but I can hear the power supply or magnetron start to hum like it is empty - something similar occurs with hot cocoa - in both cases the liquid foams and when that occurs the sound of the oven changes perceptibly.

Has anyone ever replaced a window? Mine doesn't look like mica but does look like some sort of hard mineral. It is only fastened over the opening with a couple of push in plastic pins and looks like it is intended to be easily replaced from the oven chamber without taking the whole thing apart.

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The window - or waveguide cover as it`s called - is available by the sheet. It`s either laminated mica or fibreglass[1]. You simply cut it to shape using the old one as a template. pierce the holes and replace the plastic rivets. Clean any grease and carbonised crap out of the waveguide while you're in there.

[1] Some ovens have a purpose made moulded plastic cover which may or may not be available.

Ron(UK)

Thanks for that. It makes a lot more sense than either discarding the whole oven or using it without any window (no window could become a fire hazard and really screw up the oven).

The stuff I have doesn't look/feel like mica or fiberglass. The previously burned parts (since "cleaned") appear somewhat translucent but don't heat in use.

Sorta like mica - but without the crystal structure.

Amateur radio enthusiasts have been putting plastics (dielectrics) into microwave ovens for years to see if they absorb microwave energy

- a window cover can't be that big a deal - just my trailer trash understanding of the universe.

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Having pointed out the potential risk in removing the window, the only time I've actually seen such damage happen was with my first microwave that I got for free because the window was arcing. As I'd heard how eggs explode in the microwave, I wanted to see for myself.

Such was my luck that a large chunk of egg ended up lodged in the entrance to the waveguide which caused an overload, this eventually resulted in overheating and shorted turns in the transformer secondary.

Ron(UK) gave the right answer. One extra point though, with the waveguide cover off, clean out all traces of carbonised crp, or the same problem will occur again after a while.

While you could use any non-rf-absorbent plastic outta the bin, many give off toxic fumes when they burn, and many will catch fire in style, so you should use the right type of material for your own safety.

When heating tiny amounts of stuff, which dont absorb rf well, put a cup of water in there with it. Avoids arcing occurring, and arcing turns things to carbon, which you dont want in a nuke.

NT

What suprizes me is when someone lets something like that burn that much It seems it would stink up the house and the food .

Many yard sales have nice clean microwaves for 20$ or less

OK. I have repaired my Kitchenaid Microwave twice for this problem and I am pretty sure I know what is going on and what needs to be done. The microwave energy enters the oven from the magnetron through a wave guide which is usually at the top of the oven. The wave guide opening has a cover which looks like a plastic plate and in fact it is made of a material similar to mica. After using the oven this plate often gets splattered with food or grease and after a while it becomes a kind of conductive surface which is not something you want in a microwave oven. The food or grease eventually becomes carbonized and allows trhe micorwave energy to arc over from the enrty point the surface of the plate over to the metal on the side of the opening. On my microwave it arcs over to a single sheet metal screw that holds the plate in place. Once the plate gets blackened by the arcing, it should be replaced. On my oven the part is relatively cheap; around $

10 or less. So the whole repair takes about two minutes. You remove the screw, slide out the plate, clean up the edges of the waveguide opening in case there is any carbon that has built up under the plate or around the edges and then you put the new late in place and remove the screw. It might be possible to clean up the plate (it's called a wave guide cover ny the way), but I have just replaced the part with a new one. That's the whole deal.

richf