Microwave oven catches fire. Repairable?

[[email protected]]

I have a small problem with my Samsung microwave where it occasionally
catches on fire. It last occurred when I was heating 2T of margarine
in a cup. I heard a bang, then saw the fire coming from behind a cover
which is presumably where the magnetron tube is. But I have used the
oven since, and it is still working fine. This same sudden fire
problem occurred many months before, where again, the oven worked fine
afterward. I have melted margarine like this many times since and used
the oven many times during those months, so I don't know why all of a
sudden it decides to go pyro on me.

That's the basis of my query: Can anyone tell me what might be causing
this, what to check and how to fix it so it doesn't happen again? I do
not want to risk fire when I am not around to monitor what's going on
with the oven, but at the same time, I do not want to replace it. I
have looked at getting another oven, but there's nothing that I like
as much as my Samsung. It has the size, the looks and the advanced
controls (ie. one touch, defrosting, etc) that I like.

This is a pic of what the damage looks like on the interior:

http://www.mediafire.com/imageview.php?quickkey=ezsdlmtxmvt&thumb=4


And one of the exterior:

http://www.mediafire.com/imageview.php?quickkey=csddinoyvgd&thumb=4

 

[Charles]

I have a small problem with my Samsung microwave where it occasionally
catches on fire. It last occurred when I was heating 2T of margarine
in a cup. I heard a bang, then saw the fire coming from behind a cover
which is presumably where the magnetron tube is. But I have used the
oven since, and it is still working fine. This same sudden fire
problem occurred many months before, where again, the oven worked fine
afterward. I have melted margarine like this many times since and used
the oven many times during those months, so I don't know why all of a
sudden it decides to go pyro on me.

That's the basis of my query: Can anyone tell me what might be causing
this, what to check and how to fix it so it doesn't happen again? I do
not want to risk fire when I am not around to monitor what's going on
with the oven, but at the same time, I do not want to replace it. I
have looked at getting another oven, but there's nothing that I like
as much as my Samsung. It has the size, the looks and the advanced
controls (ie. one touch, defrosting, etc) that I like.

That cover should be replaced as it is now carbonized.

 

[ian field]

That cover should be replaced as it is now carbonized.

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!

 

[Charles]

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!

I was going to mention this but decided not to. You are correct.

 

[Jerry G.]

From being in the service business, and having experience with this,

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

 

[James Sweet]

I was going to mention this but decided not to. You are correct.

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

 

[ian field]

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

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.

 

[HapticZ]

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. ;-)


ove thru a

 

[default]

I have a small problem with my Samsung microwave where it occasionally
catches on fire. It last occurred when I was heating 2T of margarine
in a cup. I heard a bang, then saw the fire coming from behind a cover
which is presumably where the magnetron tube is. But I have used the
oven since, and it is still working fine. This same sudden fire
problem occurred many months before, where again, the oven worked fine
afterward. I have melted margarine like this many times since and used
the oven many times during those months, so I don't know why all of a
sudden it decides to go pyro on me.

That's the basis of my query: Can anyone tell me what might be causing
this, what to check and how to fix it so it doesn't happen again? I do
not want to risk fire when I am not around to monitor what's going on
with the oven, but at the same time, I do not want to replace it. I
have looked at getting another oven, but there's nothing that I like
as much as my Samsung. It has the size, the looks and the advanced
controls (ie. one touch, defrosting, etc) that I like.

This is a pic of what the damage looks like on the interior:

http://www.mediafire.com/imageview.php?quickkey=ezsdlmtxmvt&thumb=4


And one of the exterior:

http://www.mediafire.com/imageview.php?quickkey=csddinoyvgd&thumb=4

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.

 

[Ron(UK)]

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.

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)

 

[default]

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.

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.

 

[ian field]

I was going to mention this but decided not to. You are correct.

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.

 

[[email protected]]

default wrote:

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.

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

 

[Charles]

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.

Good advice. Don't run those magnetrons unloaded, as the energy has to do
something.

 

[Ken G.]

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

 

[[email protected]]

I have a small problem with my Samsung microwave where it occasionally
catches on fire. It last occurred when I was heating 2T of margarine
in a cup. I heard a bang, then saw the fire coming from behind a cover
which is presumably where the magnetron tube is. But I have used the
oven since, and it is still working fine. This same sudden fire
problem occurred many months before, where again, the oven worked fine
afterward. I have melted margarine like this many times since and used
the oven many times during those months, so I don't know why all of a
sudden it decides to go pyro on me.

That's the basis of my query: Can anyone tell me what might be causing
this, what to check and how to fix it so it doesn't happen again? I do
not want to risk fire when I am not around to monitor what's going on
with the oven, but at the same time, I do not want to replace it. I
have looked at getting another oven, but there's nothing that I like
as much as my Samsung. It has the size, the looks and the advanced
controls (ie. one touch, defrosting, etc) that I like.

This is a pic of what the damage looks like on the interior:

http://www.mediafire.com/imageview.php?quickkey=ezsdlmtxmvt&thumb=4

And one of the exterior:

http://www.mediafire.com/imageview.php?quickkey=csddinoyvgd&thumb=4

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