• ** 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

Loud pop and flash

Michael9040

Premium Member
Joined
Mar 19, 2008
Messages
36
Location
Florida
Model Number
PLMVZ169HC
Brand
Frigidaire
Age
1-5 years
For several months, whenever something on the stove created steam, if we then used the microwave we were greeted with a loud "pop" and flash. Then it worked correctly. No problems unless boiling something on range prior. As it approached the end of warranty, I called a local service company who replaced the board. After that, under the steaming conditions it hummed continuously but worked. Last night it was louder than normal, smelled and didn't work. Service company tells me it needs a magnetron, capacitor and diode. Hard to believe that these problems are not related. What's your experience?
 

rickgburton

Appliance Tech - Moderator
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Location
Murray, Utah 84107, United States
The Mag Tube, Capacitor, and Diode is the entire high voltage side of the microwave less the transformer. I find that a little hard to believe that all three went out at the same time. Maybe if you were cooking nuclear waste. Was there a fire in it? I don't believe a fire would do it either. The loud pop and flash doesn't sound like the board either but that's water under the bridge. Did it go away with the new board? How long after the board was replaced did the humming sound start? Was it taking longer to cook? The loud humming and burning smell should make it easy to figure what's wrong. Something is burned in there. How comfortable are you working with electricity and do you have or have access to a VOM?
 

Michael9040

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Mar 19, 2008
Messages
36
Location
Florida
Thanks for the quick reply! The tech indicated that all three were probably not bad, but he liked to replace them together. The predictable loud pop and flash did seem to go away after the board replacement, but was replaced immediately with the humming (when moisture was present). Don't believe that there was any difference in the amount of cooking time required. We are still in "negotiations" about who is responsible for this repair. My position is that the problem was never repaired correctly while the unit was under warranty, which expired Jan 8. I am just trying to understand what the presence of moisture has to do with my problems and what to do to correct it.
 

rickgburton

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I don't know what would cause that kind of problem. It must have been something on the control board if it went away after it was replaced. Replacing the board wouldn't cause a high side component to fail, nor would moisture. It would have to be a lot of moisture to cause a short. I've never heard of replacing all the high side components if one goes out. The humming could be coming from the High Voltage Transformer. Let's get jeff1 opinion on this. He's a good microwave tech. He may have heard of this issue before.
 

jeff1

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Ontario, Canada
Hi all,

JMO!

On OTR microwave is suppose to be built to go over a range!
Why is steam effecting/effected the pcboard?

~Consumer is not turning on the fan when using the surface burners
~Why isn't the fan coming on on it's own...it should if the bottom of the microwave is getting too hot.
~Is the fan working correctly?
~Vented outside, inside?
~Venting sized correctly
~Install is wrong height above range top?

*If* this unit was going to be repaired under warranty I understand what the tech is doing....no diagnosing....order all the parts we -may- need to cover all the bases. This is a common practice today :(

Steam can certainly damage the PCBoard but shouldn't/wouldn't effect the mag/diode/capacitor!

JMO!

jeff.
 

Michael9040

Premium Member
Joined
Mar 19, 2008
Messages
36
Location
Florida
Well, Frigidaire refused to step up on this so I am faced with fixing it myself or putting it at the curb. How do I test to determine exactly which component is bad? I have another one just like it that quit working after the warranty period, but I suspect it has the same bad magnetron.
 
Last edited:

jeff1

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Michael9040

Premium Member
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Mar 19, 2008
Messages
36
Location
Florida
Like I said, I have two of these units so I took the three suspect parts from both. The readings that I was getting with my old needle multi-meter made no sense, so I just took them to a local parts house. They tested both capacitors as good and both diode/rectifiers as bad. They claimed no reliable way of testing the magnetrons and they suspected that the diode/rectifiers didn't cause their own failure. When I test the magnetrons according to your directions, I get 1-2 ohms on terminal to terminal and no needle movement on terminal to chassis. Can I assume that it is indeed the magnetron?
 

jeff1

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Ontario, Canada
It is common for the mag to hurt the diode or the diode to hurt the mag......often we do both at the same time. You have gone as far as you can in checking the mag, normally I might be inclined to try a diode only just to see what happens.

jeff.
 
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