microwave oven stopping prematurely, repairable?
tin6150
Hello folks, happy Memorial Day weekend to you all!
My microwave is acting erratic, maybe you can help me see if it is
repairable? It can heat water, but tends to shut downs prematurely.
I have read this repair faq
http://www.repairfaq.org/sam/micfaq.htm#micsaf
but didn't find answer to my problem.
One evening I was cooking a frozen dinner, a chicken pot pie with a
mesh for browning at the top of the paper container. It is said to be
microwave safe. I followed instructions exactly. But maybe 3 minutes
into the nuking, there were a few spark, so I pulled the power cord as
quickly as I could. There were some burn smell, which lingered even
after a week of non-use. The microwave oven was clean, no spill over
or splatter when I started nuking the pot pie. I did not leave a fork
in there either.
The microwave in question is a panasonic inverter system, 1200 W.
manufacture date is 2002.
Currently, all electronics seems to work fine, touch pad works, clock
runs, timer works. no visible damage. No paint problem from the
spark. I tried to heat a cup of water for 35 seconds, and microwave
just shut off automatically after some 15-20 seconds (but clock panel
still running, so the electronics seems to have shut something down.
No error indicator of any sort that I can see).
If I set power to 50%, then it will heat the water for 50 seconds to
completion. water temperature is very warm to the touch. If I set
power to 10%, then it will heat for more than 70 seconds to
completion.
Maybe eventually at more than 50 seconds even at the 50% power, it
might shut off automatically when something gets too hot? I am not
sure if I want to try it if microwave isn't really going to be fully
functional anyway.
It is likely cheaper to just buy a new one, but as an
environmentalist, I just hate to waste appliance that can otherwise
work :)
Much thanks in advance for any advices.
Tin
mike
tin6150
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
William Sommerwerck
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.
Robert Macy
> Hello folks, happy Memorial Day weekend to you all!
>
> My microwave is acting erratic, maybe you can help me see if it is
> repairable? It can heat water, but tends to shut downs prematurely.
>
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.
whit3rd
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.
TonyS
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.
tin6150
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