• ** 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

721.80523500 Fuse blown

red1958

Premium Member
Joined
Nov 1, 2012
Messages
54
Location
Puerto Rico
Model Number
721.80523500
Brand
Sears Kenmore
Age
6-10 years
I have the 250 V 20A fuse blown after a power outage. Replace the fuse and it still blown everytime I hit the start button. This is what I have done so far:

1- Disconnect fan, blower and Magnetrón. Fuse blown.
2. Connect all ítems back ( except the Magnetrón ). Fuse blown.
3 - Disconnect HV transformer. Fuse OK.
4 - Check diode and capacitor. Seems to be OK.
5 - Connect HV transformer. Fuse blown.
6 - Disconnect diode and capacitor. Fuse OK
7 - All steps from 2 are with the Magnetrón disconnected.
8 - All lights, fan, blower, display Works fine if I don't hit the start button.

Any idea about why the fuse is blowing? ( I am using a fast blo fuse. Do not have any time delay fuse.) I am thinking about replacing the diode and capacitor but am not sure if that will solve the problen. Thanks for your help.

Best Regards
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,008
Location
Ontario, Canada

red1958

Premium Member
Joined
Nov 1, 2012
Messages
54
Location
Puerto Rico
Hi Jeff:

I found a capacitor and a diode on my garage from an old Microwave but have not installed them yet to test if they solve the problem. As soon as I have a chance, I will work on it and let you know if the problem is solved or if I need to buy any other part. Thanks for your reply.
 

red1958

Premium Member
Joined
Nov 1, 2012
Messages
54
Location
Puerto Rico
Hi Jeff:

I replaced the capacitor with one with almost the same spec ( .91 mF instead of 1 mF ) and the microwave start working again. Will it makes any difference having a slighty different capacitor installed ? Will it affect the performance of the microwave? Thanks again for your help.
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
24,008
Location
Ontario, Canada
Will it makes any difference having a slighty different capacitor installed ? Will it affect the performance of the microwave?
Yes, yes.

I try to not go more than 5-10% difference.

I might sub a .95 for an 1
.91 is a bit low.

jeff.
 
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