Re: Kenmore microwave acting intermittently

Astriapo <astriapo@xxxxxxxxxxxxx> writes:

Sounds like one of the thermostats inside the case is bad. Could also
be a bad transformer.

Or an intermittent filament connection to the magnetron.

Put it on 50 percent power and listen carefully for the sound as the
magnetron kicks in. There should be a subtle change in the hum as
the filament heats up and the magnetron starts drawing power. I bet
that will be absent once it stops heating. Of course, could also
be a bad transformer, relay, other wiring, etc. This should be
repariable relatively easily though. Inexpensively unless it's
a bad transformer or an intermittent filament inside the magnetron.

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On 1 Aug 2003 19:32:50 -0700, beanie_bari@xxxxxxxxx (Beanie) wrote:

Okay, so I've tried everything possible to get a microwave that was
picked up off the street to work. It's a Kenmore 565.8925590, 1300W,
serial 1V7C01490, manufactured September 1991. The magnetron and
controller IC are made by Sanyo, so I imagine that the entire oven
was, too. So, here's the symptoms the microwave exhibits:
The microwave will happily begin to microwave a cup of water. After
about a minute or so, the fan and the turntable will stop. The light
stays on, and the counter keeps going. If I stop the microwave cycle
and let the oven cool down, I can start it up again, for about another
minute. So, I opened it up, and checked the usual suspects (fuse,
interlock switches, etc.) The primary interlock switch was always
open, so I replaced it. That didn't fix anything. All of the
switches appear to be making good contact with the actuators on the
door. There are two thermal protectors. Both offer a resistance of
zero, and according to the schematic (and the actual wire routing) if
either opened, it would kill power to the entire oven--so I know that
they are not at fault here. The magnetron does become hot to the
touch, but it's not _that_ (135 degrees centigrade) hot.
As far as I can tell, the only thing left to be at fault is the
relays, that are located on the controller board. I'm a little leery
of testing the relays on it with the oven live--especially because the
warning labels clearly state that the step-down transformer will give
me a jolt. :-) There is a burn mark on the PCB in the center, but the
resistors, diodes, and caps in that area all test fine.

Any suggestions?

Thanks!

--Chris
.

Relevant Pages

  • Re: microwave oven power cooking levels?
    ... > attain different power levels, panasonic call this inverter technology, they ... The inverter substitutes high frequency electronic switching and a SMALL ... transformer for a much heavier magnetic transformer to provide the high ... voltage necessary to operate a magnetron. ...
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  • Re: Work Proceeds- Experimental Status
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    ... A basic power as slow quanta appears the cause to the anomaly. ... 1kW laser can equal a 1kW magnetron. ... And so I decided to follow a basic design method of ducted microwave. ... A single magnetron to power a rotating set of waveguides. ...
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  • Re: Microwave oven
    ... How can one test the heating power of a microwave oven: Perhaps by heating a known quantity of water to a desired rise in temperature over a prescribed time period? ... It`s also important to check the spade connectors on the magnetron, these sometimes become loose and erode away making intermittent contact for the heater current. ...
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  • Re: microwave riddle?
    ... That's the transformer winding that supplies 3VAC to the magnetron's ... when eithermicrowaveor grill cooking is started? ... "An open HV diode will result in AC instead of DC across the magnetron ... then I'd be looking at the power transformer ...
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