• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

    Jake

PLMV168CC1 Frigidaire OTR not heating - advanced tests needed?

prskier17

Member
Joined
Apr 2, 2017
Messages
1
Location
Minnesota
Model Number
PLMV168CC1
Brand
Frigidaire
Age
More than 10 years
Hello,
I have a Frigidaire PLMV168CC1 over-the-range microwave purchased and installed in about 2004. Recently the microwave stopped heating. All functionality when attempting to heat works as always (display, timer, fan, light) and the only symptom of the issue is that no actual heating occurs. I have already done a substantial amount of testing to include:

1. Confirm all three door interlocks function properly.
2. Test HV diode (I replaced the diode as I initially thought this might be the issue and they are inexpensive). Turns out the original diode is still good.
3. Test HV capacitor (as much as possible using digital Fluke 87 meter with analog like indicator to see charging and discharging with two 9 volt batteries)
4. Test all thermal switches and confirmed NO or NC per the schematic located within the appliance.
5. I have measured the resistance of primary and secondary windings of the HV transformer. The secondary side was ~5 ohms higher than spec. The primary side was normal.
6. I have measure the resistance of the magnetron and it measured what what was suggested on multiple internet sites.
7. Finally, I can confirm that when I attempt to heat there is 120VAC at the primary side of the HV transformer. I have to tool capable (nor do I want to) of measuring the secondary voltage of the HV transformer.

Questions:
1. Am I correct in assuming that the issue is either with the HV transformer or the Magnetron (since I'm getting 120VAC at the HV transformer primary)?
2. Would a useful HV transformer test be to connect a lower AC voltage (from a doorbell transformer, etc.) to the primary side so I can measure the secondary side?
3. What else can I do to troubleshoot?

Note: I was ready to write this microwave off and purchase a new one until I discovered that all the new OTR microwaves vent (at least the microwave portion, not necessarily the range hood) from the top. This microwave and most others from this vintage have front facing vents on top. Our kitchen cabinet directly above the microwave is approx. 19" deep. All of the current microwave require a max cabinet depth of 12 or 13 inches and we don't want to butcher our cabinets or mount the microwave 6-7 inches from the back wall. So... although this will eventually be an issue I am motivated to fix this! Thanks in advance for any replies and advice!
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
23,618
Location
Ontario, Canada
Hi,

A copy:

*Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it. With the microwave unplugged. *

Confirm 110-120 volts AC is entering the primary coil on the high voltage transformer....meter works but can be fooled, I usually rig up a light socket and household light bulb and hook that to the 2 input wires for the transformer and see if the light works or not when you run the microwave....can even set a power level and watch the light go on and off. Discharge the capacitor first before attempting any checks or tests.

Scary but works!....

If ok, put those 2 wires back on the transformer. Discharge the capacitor.

Remove the 2 wires going to the magnetron....run the microwave a few seconds ( 2-3 ) and remove power....again discharge the high voltage capacitor. If you got a good crack & spark when you discharge the cap the second time you are creating high voltage but not using it ( bad magnetron or loose High Voltage wire somewhere )....if you get no crack & spark you are not creating high voltage. This will work on all microwaves with a transformer and diode system ( not the inverter style ).

If needed:

Magnetron-5304408930--00833701.jpg LINK> Magnetron

jeff.
 
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