(Harry Hotspur) writes:

On 6 Jan 2005 20:04:23 -0800, "electroninja" wrote:

Sharp Model R1810 Carousel II microwave starts and cooks(heats) but
shutsdown after about 40 seconds. Electronic control board display
stays lit, countdown stops and displays remaining time--magnetron
cooling fan works during the first 40 seconds but then shutsoff--just
before shutdown, fan speed increases(doubling or tripling in speed)
These items seemed to check out good with VOM--
power fuse
interlock switches (2)
monitor switch
capacitor
diode
thermal cutout switch(only found one)
fan motor
power tranformer

Additional trouble shooting note--a power surge protector I had plugged
the microwave into was discovered fried--suspect a near by lightning
strike?

Read an informative article by Sam Goldwasser-- "NOTES ON MICROWAVE
OVEN FAILURE DIAGNOSIS AND REPAIR v1.01" but need more help. Thanks

Clear the mag first so::Go to the Mag filament wires{ be sure the HV secondary
wire is removed} then test for between 2.9vac and 3.9vac depending on model

Can't overemphasize this. There may be up to 5,000 V at very lethal current
availability present on the magnetron filament wires while operating with
the high voltage capacitor holding a dangerous charge after shutdown.

ANY testing in the microwave oven high voltage circuits is extremely dangerous.
Very knowledgeable and experienced professionals have been killed doing this.
It's too easy to be careless and you don't get a second shot.

If you insist, while unplugged, make sure the HV cap is discharged, then
hook up meter, stand clear and turn it on. Take reading without touching
meter including its test leads, power down and remove plug from wall socket,
discharge HV cap. Etc.

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when powered up.Replace Filament wires and re-coneect clipping test leads to mag
terminals and check again at switch on for the same a.c. voltage.A lower voltage
can be the result of the mag lowering the filament transformer voltage.Move on
from there if correct but get the MAG out of the loop first.