After a recent thunder and severe lightning storm my microwave oven stopped working; or I should say stopped heating. I'm quite certain that it took a surge. Everything I have read points to a varistor. I found it on the circuit board (it's an INR 10N471). There was someone on this site that had a similar problem and was advised to take it out of the circuit and check for an open or short; which I did. It read "open". Another person on this site said that it could read "shorted" which would mean it was definately bad, or it could also read "open" that could mean it was still good OR had been coupletely blown. From the little electronics that I received in the U.S.Navy, I figured that if it was already "open" then taking it out of the circuit and trying to operate the appliance without it, at least, would do no further harm. I plugged it back in and, sure enough, it still doesn't work. I THOUGHT I smelled a slight burning around the circuit board but it might just be my thinking the worse; I'm not sure.

My questions are, to anyone with more knowledge than the little bit I have: Should I replace it anyway? Have I likely caused more damage by plugging it in for a short while with the varistor out of the circuit? If it read "open", then it was really out of the circuit anyway, wasn't it? I can see no visible damage anywhere on the board and am lost.

I am leaving on a trip with my wife in a couple of days and any help in getting the thing fixed before then will avoid the dirty looks I'm likely to suffer until we return!

Thanks, [email protected]

 

You are on the wrong track. The varistor may or may not be bad but as long as it is not shorted, then it has no effect on normal operation. The microwave may be safely operated without the varister in place. The components that most frequently fail in microwaves are the power diode or the filter capacitor. However neither of these components would fail unless the device was in use when the lightning struck. You have not mentioned the fuse. The fuse usually trips when either the diode or the capacitor goes. Have you checked it?

Fred Townsend

 

Hello my friend

1. I don't think this is an appropriate place to discuss domestic appliances.
2. It is extremely reckless for a home handyman to attempt the repair of a microwave oven. The magnetron circuit generates lethal voltages. Take the microwave to a service center.
3. "everything I have read points to a varistor" ???. You have a faulty appliance. It needs to be looked at by a technician!!!

 

Your varistor, (or variable-resistor), will read open if good and it shorts out when the input voltage exceeds it's rated break down voltage, sending the spike to ground. This often blows the part and is usually visable with a lightning hit. You will not damage anything by removing it from the circuit, you just won't have surge protection. If you tried it without the varistor and it still didn't work you probably fried the electronics, (lightning can be faster than a varistor or just too much for it to clamp). Spend the $50 bucks and have it looked at or invest it in a new one... You never know, she might have wanted a different color anyway, and it goes towards the deductable on your home owners insurance.

 

Dear Russell Dimond:

To give you a brief idea of the various kinds of electronic components now available for export, we introduce one of salable components (Varistor, surge absorber) as an experienced professional manufacturer, the following:

Our factory was registered in the year of 1989, lies in the city of Chengdu, which is specialized in producing varistors with ¡°TIEDA¡± brand and has annual capacity of 100 million pieces. The factory has early passed the ISO9002 in 1995, and has obtained the CQC Certificate of China and UL-Safety Certificate of the U.S in 2000.

There are two kinds of varistors in our factory, one is low voltage varistor, medium and high voltage varistor (called: Traditional varistor), another is varistor with thermal protection (the newest one). They are applied for Electronic Dynamometer, Surge suppressing distributor, Transistor, diode, IC, thyristor or triac semiconductor protection; surge protection in consumer electronics such as refrigerators, color TV, air-conditioner etc. Surge protection in communication, measuring or controller electronics, surge protection in electronic home appliances, gas or petroleum appliances, Relay or electromagnetic valve surge absorption etc.

Very very especially, our factory put out the new varistors with good quality which could be replace traditional varistor with special design and function from now on. It is the Varistor with thermal protection function (Thermal MOV). The products have gained national patents (No.02222055.0). A new chapter in the history of surge protection has been written with the creation of our Varistor with thermal protection function, which has also invented it for your customers.

More information, please view our website: www.chinagok.com/tieda.htm


If you have some question, please contact us soon.


Yours faithfully



WANG