13 replies to this topic

[Tarheel Technician]

I have a microwave, model # GMH6185XVS1, that runs but doesn't heat. The HV diode, magnetron, HV capacitor, and the HV transformer all check good. Primary, secondary, and & monitor switches check good. Fuses and tstats all check good.

I'm a little confused as to the 'Turbo Relay' that is on the wiring diagram. One leg of that relay comes through a 20 amp fuse to the HV transformer, and I'm getting 120 volts there when microwave runs, but the other leg of that relay (brown wire) goes to HV transformer as well, and I get nothing there. The wiring diagram is attached.

Thanks for any advice!



https://servicematte...- W10268748.pdf

[RegUS_PatOff]

... 'Turbo Relay' ... One leg of that relay ... I'm getting 120 volts there when microwave runs,
... the other leg of that relay (brown wire) ... and I get nothing there.

120v,at the Transformer Black wire ?
referenced to neutral ?

I would think there should be 120v at the Brown wire also
if the Transformer is good
Check continuity between Transformer Black to Brown

Are there any error codes ?
Was the M/W Fuse blown ?
Was there any "spark" when you discharged the HV Capacitor ?

[Tarheel Technician]

I was checking with one of the leads of my meter on the white wire going to the HV transformer, and the other lead checking both the brown and black wires separately.

I checked the voltage with the wires off of the transformer, just checking to see if voltage was getting to the transformer. That's why there was no voltage at the brown wire. However, I was thinking there should have been voltage at the brown wire even with the wire off.

There is continuity between transformer black to brown.

There were no error codes, the fuse wasn't blown, and there was no 'spark' when I discharged the HV capacitor.

With everything hooked back up, the microwave hums like it is heating, (sounds like a normal hum, not an overly loud hum). With that being said, I was pretty sure there would be a magnatron, diode, or cap problem, but everything is checking normal. I checked the diode with a 9V battery, and it lets about 4 volts through.

[RegUS_PatOff]

HV Capacitor reads "something ...& ... increases"
in each direction, with OHM meter ?

[Tarheel Technician]

Yes, needle momentarily goes to the right, and slowly back to the left in each direction.

[appl.tech.29501]

HV Capacitor reads "something ...& ... increases"
in each direction, with OHM meter ?

Decreases.....


Also, what was ohms value on the magnetron filament?

[Tarheel Technician]

The mag filament according to my digital meter reads .9 ohms, but when I touch my leads together, it reads .9 ohms, so it virtually reads 0 ohms.

And infinity from each mag filament to chassis.

[appl.tech.29501]

Most mags ohm at 0.03 I would check it with a different meter. There also should have been a spark when dischargeing the cap.
disconnect the wires going to the magetron tube filament and run the unit for 30 sec.
And then discharge the cap. If you don't get a spark then you know its a high voltage component other than the magazine tube (as long as you have 120v at the transformers primary) .

If you get a spark then you have a bad magnetron tube.

[RegUS_PatOff]

Decreases.....

... hmm.. at first I had written "decreases", but after reading my message, I edited it to "increases".
When first connected, the Capacitor would seem like a "short" (near 0 OHMs) (maximum right on an analog meter)
and "increase" in resistance (to the left on an analog meter) until it is charged.

..

[Samurai Appliance Repair Man]

When you tested the magnetron, did you apply the Willie Method™ ==> The Willie Method™ for testing a microwave oven magnetron tube

[Tarheel Technician]

I will apply the Willie Method in the morning and post my results. Thanks to everyone for the help!

[Tarheel Technician]

After applying the 'Willie Method', I did not smell any unusual smell, and I did get a spark when discharging the capacitor. Before I did this, I did check the mag with a different meter and got .003 ohms. Gonna look up the the cost of a new magnatron! Thanks! Gonna help out the beer fund!!

Just out of curiousity, why would the capacitor spark after running it with mag unhooked, but no spark when wires are hooked to mag?

Edited by Tarheel Technician, 01 March 2012 - 09:47 AM.

[RegUS_PatOff]

... why would the capacitor spark after running it with mag unhooked, but no spark when wires are hooked to mag?

That HV Capacitor has a self-discharge resistor inside of it.
Depending on when it was last "charged" and the time lapse before you tested for a spark.

[Budget Appliance Repair]

Running with the mag attached, (and the mag being bad), the capacitor doesn't get charged enough to give a discharge spark.

Running with the mag out of the system there is no place for the charge in the capacitor to be discharging too so you get a good spark when you discharge the capacitor, IF the hi-voltage system is working correctly.

As far as I know when everything else including the mag tube checks OK and you're not getting any heat this is the only way to prove that the mag is the problem and not something else in the hi-voltage system.