• ** 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

FIXED 721.86002 Power surge and now dead

Zorky

Premium Member
Joined
Jun 24, 2017
Messages
10
Location
Ohio
Model Number
721.86002
Brand
Sears Kenmore
Age
1-5 years
This is a brand new unit but 3 years old. Was a display in a model home and never even powered on until we got it. Long story short. We had a severe power surge 3 days after owning this due to a power company issue. It is completely dead. I am knowledgeable on electronics and have the unit disassembled. Everything was discharged. Capacitor is a 1.05uF and test good. Diode test open circuit. Thermal and magnetron fuse test good. I have 120 hitting the input of the transformer. I am suspecting the transformer is bad. The only ohm reading I am getting is on the secondary winding of 90ohms. Getting OL on primary winding and filament. I don't really know how to test the board. I am not seeing anything blown or burnt on the panel board. The fuse on the noise filter assembly never blew. Could a transformer blow without the 20a fuse on the noise board blowing? Does the transformer always produce voltage when the microwave is plugged in?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,737
Location
Murray, Utah 84107, United States
We had a severe power surge 3 days after owning this due to a power company issue. It is completely dead.
"Completely dead" means no lights, no display, no sounds. However you're saying you have 120 VAC at the primary windings on the high voltage transformer?? Can't be.
 

Zorky

Premium Member
Joined
Jun 24, 2017
Messages
10
Location
Ohio
Not sure about primary winding, I had 120v at the input wires feeding HV transformer. Found the PCB is bad. Traced power from the cord clear through the PCB and I had 120v hitting the input of the HV transformer. I did not have the HV transformer plugged in for obvious reason. I don't know if the primary winding had voltage. I know I have 120v hitting the input of the HV transformer. Unit is completely dead. No noises, lights, display or anything.
 

Zorky

Premium Member
Joined
Jun 24, 2017
Messages
10
Location
Ohio
Not sure how to mark this thread as fixed. But this issue I had ended up being the low voltage transformer. Had voltage up to and passing through the control board to the input of the low voltage transformer. Had no power coming back to the control board on the 6 pin connector from the low voltage transformer which is what actually fires up the control board functions. Coils appeared to be open windings.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
102,155
Location
McMullen Valley, Arizona
You HIGH VOLTAGE transformer here: 6170W1D100G

I see no low voltage transformer on this model.

Jake
 

Zorky

Premium Member
Joined
Jun 24, 2017
Messages
10
Location
Ohio
This does for sure has a LV transformer. Part number EBJ56679201. This sits directly below the noise filter board assembly and fuse.

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