Microwave no heat

[Alex Belenkiy]

Good afternoon everybody,
my first question/post.

I am trying to repair a Frigidaire over the range microwave, it runs and counts down but no heat.
I have followed some troubleshooting videos from youtube to no avail.
Troubleshooting done so far:
Reset power to ensure it was not setting related.
Putting a glass of water in the microwave even for 5 minutes does not produce anything.
Opened the unit and tested each of the door opening switches.
Checked the high voltage diode for connectivity utilizing a 9v battery and tongue the voltmeter continuity test did not read it.
No components are burned anywhere.
Checked all thermal switches, NO and NC are all fine. I did not heat them to tripping point however.
Disconnected each high voltage part to test coil resistance and possible short to ground.
Tested the capacitor, it showed the proper uF as per the label.
Tested with a capacitor/diode set from an old microwave i took apart a long time ago.
The primary coil of the high voltage transformer gets 120V when the unit is running.
I do not have a high voltage voltmeter attachment to test the secondary side, but all of the coils seemed to be fine.
I do not hear the louder sound while cooking, leads me to the magnetron as the culprit.
Please let me know if i am missing anything in my testing, or what else i can look at or try.

thank you
Alex Belenkiy

 

[davenn]

The magnetron has probably failed
that's the most likely ( a smaller possibility is that one of the interlock switches has failed
this will stop power to the magnetron

Dave

 

[Alex Belenkiy]

Thank you for replying.
I was thinking of the switch, but if it was one i would not get 120V across the primary coil. It would have been shorted to ground or not getting anything.
Most likely you are right its the magnetron.

 

[Alex Belenkiy]

I made a voltage divider and was able to measure the high voltage side as follows:
194V from small winding that goes to the magnetron. Magnetron disconnected.
2786V between high voltage transformer output and ground. Capacitor/diode and magnetron disconnected.
3745V across capacitor. Magnetron disconnected, diode attached.
3438V across diode. Magnetron disconnected, capacitor attached.
Do these values look right for this model?
Frigidaire FGMV174KFC

 

[davenn]

without specific service info for that unit ... I cant answer that

 

[Alex Belenkiy]

I decided to take a chance and order a new magnetron. About $70 and if it doesn't fix the problem i will return it with a %15 restocking fee. Figured it was worth the risk between the shipping and restocking costs before buying another oven for $300.
Will update here the final outcome.

 

[Alex Belenkiy]

Alright, i paid around $70 for a replacement magnetron, i could have gotten a similar one for $25-$40 but opted for the exact same one to be safe. As soon as i installed it i tried to turn on the oven just to find that it was completely dead now. Checked the fuse and indeed it was shot, not sure how it died from when i last worked on the over to when i received the magnetron. Kids are not admitting to plugging it in while i had parts removed
Replaced the fuse with one i bought in Home Depot for a few dollars. Microwave is working perfectly now and is heating much better than when it was "new" (i bought it off the display in PC Richard).

Thank you for all your help, hopefully my post will help someone as well.
sci.electronics.repair was a great troubleshooting resource.
http://www.repairfaq.org/REPAIR/F_micfaq7.html

[advertising removed]
Will try to post some pictures if i have time of the repair.

Voltage divider - $5
Magnetron - $70
Fuse - $3
Knowledge gained - priceless...

 

[the great potato]

Great to see you fixed the issue! My guess was the magnatron failed. Great job.

 

[davenn]

Great to see you fixed the issue! My guess was the magnatron failed. Great job.

this thread is over 5 years old !