Jenn Air Microwave blows fuse

[RogerW]

Model Number

JMV8208BAS

Brand

Jenn-Air

Age

6-10 years

I have a JENN AIR JMV8208BAS microwave that keeps blowing one or both of the two internal fuses on the noise filter board. I have replaced the HV capacitor, diode and magnetron. I tested the HV transformer and thought it was ok but now an appliance repair service tells me that the HV transformer is bad. I'm not sure that I believe their conclusion because when I unplugged the HV transformer, magnetron, capacitor and diode and then started the microwave the second fuse on the noise filter board blew.

I've also tested the door switches with an ohmmeter to verify that they're working. A repair technician said that the door switches could blow the internal fuse but I don't understand how that's possible if they don't connect to ground. I have also run various test with items disconnected to try and isolate the short. I disconnected the blower motor, mixer motor turntable motor and the fuse still blew.

I'm thinking the the short has to be on the main control board.

 

[rickgburton]

....an appliance repair service tells me that the HV transformer is bad.

Here's how to test the HV components:

I've also tested the door switches with an ohmmeter .... A repair technician said that the door switches could blow the internal fuse but I don't understand how that's possible....

Test the microswitches with your meter by opening and closing the door. Check the latch levers on the door and make sure the spring isn't broken by lifting up on them. The spring should pull them down. The monitor microswitch is also called a "dead man switch" It's a normally closed switch with the L1 and N wires connected to it. When the door is closed the switch is open. Designed to keep the microwave from operating with the door open it creates a dead short between L1 and Neutral and blows the fuse.

 

[Jake]

Rick I re-upload your HV component testing photo, it didn't go through the first time.

Just a friendly note to anyone following this thread to do first before testing HV components.

(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

 

[rickgburton]

OK Thank Jake

 

[Jake]

Your Welcome Rick.

Jake