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John, restaurant equipment technician
Category: Appliance
Satisfied Customers: 2136
Experience:  25+ years experience. I'm now employed by a commercial cooking equipment service company
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My samsung microwave stopped. No power whatsoever. Tripped

Customer Question

My samsung microwave stopped. No power whatsoever. Tripped circuit breaker, reset
breaker and microwave and it went out again and nothing works. Outlet is fine.
Model SMH7174.
Submitted: 5 years ago.
Category: Appliance
Expert:  John replied 5 years ago.

Were there any noises, when the microwave tripped the circuit breaker?

If my answer helps you, please click on the 'accept' button. That's how we experts are paid for our efforts.

Customer: replied 5 years ago.
It was kind of making a loud humming noise, not the normal sound.
Customer: replied 5 years ago.

I had a friend here and he had plugged in a battery charger for his cordless power tool,

I know it said 19 amp on top and it was plugged into an outlet for the same circuit

breaker as the microwave. The refrigerator and dishwasher are on the same circuit

and we have never had any trouble until the day he had that charger plugged in.

Also I am going to be in and out all day, so my responses will be slow, I apologize.

Painted soffits.

Expert:  John replied 5 years ago.

OK. Thank you. The noise is generated by the transformer in the magnetron power supply circuit, when it fails and short circuits to chassis ground. The oven is dead, because the fuse that protects the control board opened to keep the board from being damaged.

The transformer will need to be replaced, as will the fuse. The part number for the transformer is(NNN) NNN-NNNN and the price is $76.85. You can buy it at You can buy replacement fuses at any good hardware store.

You can locate the fuse holder by removing the oven cover, and following the black wire that connects to the power cord.

John and other Appliance Specialists are ready to help you
Customer: replied 5 years ago.

Okay. So how to remove the oven cover. Its an over the stove model attached to the

wall, do I have to take it down?

Expert:  John replied 5 years ago.

Unfortunately, yes. The U shaped cover fits over the sides and the top, with hold down screws along the back edge, and in some cases, along the bottom edges on the sides.

When all those screws are removed, pry the sides out at the rear bottom, and lift the cover up and back toward you. The cover usually has slots at the front that fit into tabs on the frame. It's similar to removing a cover from a radio.

Customer: replied 5 years ago.

John. You online. I am finally able to work on my microwave.

I thought that I would try the fuses first, got power and sounded normal for about

5 seconds and then went dead. So transformer first, then fuses, huh?

They are out of stock until at least Nov 30th.

But am I on the right track?



Expert:  John replied 5 years ago.

Did you hear any unusual noise while it ran for the 5 seconds, and did the inline fuse open again?

Customer: replied 5 years ago.

No unusual noise. Thought I was going to have a cup of tea. But then it went dead

again. Did not trip breaker, just went dead, assuming the fuse?

Expert:  John replied 5 years ago.
Yes. The fuse I'm speaking of is in the power wire that goes from the power cord connection terminal block to the fuse holder that's located behind the control board. Is this the fuse you replaced, and is it the one that opened up again?
Customer: replied 5 years ago.

I guess so. There were two of them that I replaced. Like an inch long, looked like

regular fuses except you couldn't see through them.

Hardware store said it was the right one.

Expert:  John replied 5 years ago.
Without any noise clues, it's hard to diagnose the problem from a distance. It's going to take a technician with test equipment to track the problem down. I'll opt out of the question, so other experts can respond.
Customer: replied 5 years ago.

Okay. Thats kind of what I was thinking. I am going to just buy a new microwave. If that part is $76 plus shipping and we don't even know if its the right one, it could be just as

cost efficient to go with a new one. I think I will actually get a smaller one, this one is a monster. Much appreciation for your honesty and assistance.


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