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foxie  
#1 Posted : Tuesday, April 1, 2008 6:00:39 PM(UTC)
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foxie

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Joined: 4/1/2008(UTC)
Posts: 3

microwave makes load humming noise and has a smell of something electrical shorting out. i took it apart and tuned it on with the cover off and found that the transformmer was arcing and making sparks. i ordered a new transformer from you # WPL815095 and installed it and now when you turn it on it blows out the fuse on the power lead. i tried disconnecting the wires from the transformer to the capacitor and to the magnetron and then start it and the fuse will not blow out. then i hooked up wires to the capacitor but not to the magnetron and the fuse will blow out. i found that if i disconnect the diode on the one capacitor wire from the ground screw that the fuse will not blow out even if i hook up everything but the diode the unit will run but found out it will not heat up anything. i tested the diode and can not get any contiuity through the diode either way. tested the capacitor and there are 3 ohms at first then it will slowly go to 9.66 ohms. checked the magnetron ohm reading across terminals and had .3 ohms and no reading from case to terminals on either capacitor or magnetron. i reinstalled old transformer and is arcs when its on but will not blow out the fuse .
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glen65  
#2 Posted : Tuesday, April 1, 2008 7:07:33 PM(UTC)
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glen65

Rank: Advanced Member

Groups: Senior Expert
Joined: 3/31/2008(UTC)
Posts: 322

First off you need to put the new transformer
back in.

Then disconnect both leads from the magnetron
and test the high voltage diode and capacitor.
You will need to make sure that
your meter has at least a 6volt battery (preferably 9v)
so that you don’t get a (false open) reading on the diode.
You should get a reading with the meter probes
connected in one direction and nothing (or infinity) when you
reverse them.

Now check the capacitor again.
Have at least one terminal of the high voltage
capacitor completely disconnected when checking it.
You should briefly get a reading then it should go
to infinity.
If the readings you gave earlier are correct then the
cap is shorted. (or possibly the internal bleed resistor is
shorted).

Double check the magnetron,
Completely disconnected and check
for continuity between each terminal and the case.
You should get nothing, even on the highest setting.

Good luck
foxie  
#3 Posted : Wednesday, April 2, 2008 6:06:47 PM(UTC)
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foxie

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Joined: 4/1/2008(UTC)
Posts: 3

i rechecked the diode and do not get a ohms reading either way. checked the capacitor and sometimes i will get a ohms reading when i test the two terminals but now i get nothing.the megnatron has no continuity from either terminals to the case but there is between the two terminals. i think it may need a new capacitor and the diode but dont know if i want to put a $100 more parts into it not knowing if that is going to fix it for sure. and it shows you dont have the diode instock
glen65  
#4 Posted : Wednesday, April 2, 2008 7:03:37 PM(UTC)
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glen65

Rank: Advanced Member

Groups: Senior Expert
Joined: 3/31/2008(UTC)
Posts: 322

What is the make and model number or (if radioshack the catalog number) of your meter and what kind of batteries does it take?
foxie  
#5 Posted : Monday, April 7, 2008 3:23:05 PM(UTC)
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foxie

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Joined: 4/1/2008(UTC)
Posts: 3

the meter i was using is a FLUKE #73 with a 9 volt battery. i found a used diode and capacitor and tried them and it will still blow out the fuse. it will dim the lights on the pannel with the clock and it makes a loud humming noise. if i disconnect the wire off the transformer that has the spade terminal on the transformer that connects to the capacitor it will not hum loud and will not blow fuse.
glen65  
#6 Posted : Monday, April 7, 2008 4:25:22 PM(UTC)
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glen65

Rank: Advanced Member

Groups: Senior Expert
Joined: 3/31/2008(UTC)
Posts: 322

From the way you describe it,
it looks like you have a bad magnetron.

If your pulling the high voltage wire that
goes to the transformer and the fuse stays in
tact, and you are certain that the high voltage
cap and diode are good, then the only thing in the
high voltage section on this unit thats left is the mag.
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