Kenmore Microwave Oven goes belly up - twice in 2 years.

[RF]

Hi Experts,

I have discovered which oven not to buy but it's a bit late now. The Model Number is: 72163252301 and, within the warranty, it made a loud pop, then started a very loud buzzing and finally a smell of burning plastic. I pulled the cord and brought it back to Sears. A week later I had it back. That is just about a year ago and it now has repeated.

This oven was very lightly used - not more than 20 mins/day.

If anyone has had this experience I'd appreciate the info. I also note that the way it is assembled seems to make access more difficult.

Please advise.

Thanks :-)

PS, my last microwave was a GE and it lasted 20 years without repair. Now you know an idiot when you meet one :-(

[Tony Hwang]

Hi, I always have good luck with Panasonic ones.

[Jon Danniken]

The way it is assembled is specificallly designed to make access difficult. There is a power supply inside of that unit capable of producing 4000 volts at a half an amp, which is guaranteed to kill you.

As if that wasn't enough, the capacitor can retain sufficient enough energy to cause a ventricular fibrillation long after the unit has been turned off and unplugged.

Microwave ovens are rather simple devices, but unless you have the specialized know-how in dealing with them, your life isn't worth it.

Jon

[Don Phillipson]

Inspect the unit looking for indications its fire safety was tested by the Underwriters Electrical Laboratory or something similar. If not, your local fire service may be able to advise where to send it.

[Jon Danniken]

Well "Smitty", I don't think your perspective of high voltage/high current appliances is a very practical one. Beyond that, suggesting that the innards of a microwave are anything less than lethal is beyond negligent, and I'd say foolhardy as well.

Jon

[RF]

Thanks to everyone for the discussion.

The only safety factor mentioned on the oven is that it is UL Listed.

This is a comment from Sears: "Sears offers a great website where you can ask expert technical questions, search for answers from other homeowners, find product manuals and trouble shooting guides. All of this and other great advice and ideas can be found at

"

Has anyone visited "this great website" and found some useful info?

[Franc Zabkar]

On Sun, 27 Sep 2009 12:16:33 -0700, Smitty Two put finger to keyboard and composed:

This may help.

Parts & Exploded Views:

Be careful of item 5000:

- Franc Zabkar

[JIMMIE]

uwave ovens arent any more complex than a regular thermal oven. The magnetron requires a few thousand volts so you have a very simple high voltage power supply. You have a timer for on/off and you have a bunch of saftey switches that makes sure the door is closed.

Jimmie

[sligoNoSPAMjoe]

Microwave ovens are designed as throwaways. They are not designed to be repaired. Considering the cost, it is not at all bad that they are designed that way. The cost of repair, even a simple repair is likely to be a a large % of the original cost.

As already noted, they are potentionally dangerous to work on. So I suggest that the 1950's, when repairing appliances was the norm are over and you need to get into this century.

[RF]

Many thanks again to all. Some good news.

I went through my files and found the report on the last repair. The problem was:

"107 Found diode shorted and arcing."

The part number is 6851W1A002A and it costs about $8.

Now to pick it up. It also has me wondering how long this one will last. This will be the third diode in 30 months. Seems to me like this product is undersized or similar.

[HeyBub]

Get a bigger diode.

[stan]

I agree with Jon. The innards of a microwave CAN be lethal. That doesn't mean any more than standing under car on a lift WILL be lethal! BTW I am a retired electronics and radio transmitter technician and manager! But it is very much the sense and capability of the d-i-yer that comes into play. e.g. I have one neighbour about whom every one shudders when he even looks at electrcity, no matter how often you try to teach him. He's the kind that says "Well can I put a screwdriver between there and chassis. My brother says that will test the high voltage !!!!!". He is dangerous with any voltage over 12 volts and he doesn't even understand that unless he can clearly see a broken off or corroded wire on his truck! Recently an acquaintance asked us to 'look at' his favourite microwave. He'd opened it and couldn't find the problem. He felt it could be the control board!!!!! My son, also a technician, and I fixed it in about 15 minutes on the kitchen table; a bad door micro-switch! The control board and the hi- voltage and magnetron circuit worked fine once we replaced the defective micro-switch (I have a jar of used ones salvaged from old m.waves). While working on it we defeated the hi voltage to the magnetron. For safety. When the owner had reassembled his m.wave he had not put the cover back on correctly and there was a potential leak on the right hand edge very close to the door opener and close to where one would put a hand to program or switch off! The 'edges' of the cover and the case were improperly meshed ............... Strewth; do wish people wouldn't touch stuff they don't understand! For example I know nothing about automatic transmissions so I would not 'go at' one. I'm also a very poor plasterer, so hands off. Everyone having fun? Within their capabilities.

[Stormin Mormon]

I'm reporting you to SPCEP, or Society for Prevention of Cruelty to Exclaimation Points.

[Tony]

I've repaired 5 or 6 microwave ovens and the problem was always a bad micro switch. Most of the bad switches were caused by a slip on wire connector making poor contact and getting hot, so I often soldered the wires to the new switch.

[Stormin Mormon]

The couple I've done, it's been the high voltage diode that goes.

[stan]

Interesting. Good idea though. We had a total of three or four m.waves in a school cafeteria we used to operate. With those and requests from friends and neighbours we had 2 or 3 bad magnetrons, which even used cost around $30 so unless you had one out of a scrapped unit hardly worth fixing! Couple of those over-heat switches (either little round bi-metal or occasioanlly solid state) that went open, Two IIRC bad micro switches, one bad diode and or capacitor can't recall which. Then also encrusted dirt, bad fan etc.

[Tony]

Well I sent them to you since I stock micro switches but no HV diodes.

Curious, what are the symptoms of a bad diode? I just thought about it, I suppose they (almost)never short out, and an open one may act as if the oven was working but nothing gets hot?

[stan]

The diode is in a simple partial voltage doubling circuit. If it dud I think you'd get AC at reduced voltage on the magnetron? Probably not high enough to produce microwaves? In simple terms IIRC the HV capacitor (usually about 0.8 mfd.) charges up on one half cycle (60 hertz) and then discharges on the opposite half cycle in series with the already charged capacitor. Thus providing pulses of HV DC at approximately twice peak voltage of the transformer HV winding output. A recent bench test showed that one particular transformer had a 21:1 ratio. So with 115v RMS into the primary, the HV would be 2415 RMS and somewhere around 3400 volts peak. Double that minus some losses etc. we are looking at around 5000 volts DC. And unlike the HV in a colour TV which is a few milliamps or even microamps to a picture tube CRT, in a high impedance circuit, the power fed to a magnetron can be a quarter to half an amp or more; at around 5000 volts DC!!!!!!!! Anything from 750 to 1500 watts etc. Welcome to your own private electric chair; eh? Cheers.

[Stormin Mormon]

No heat, loud hum. And, I sent you the ones with the bad microswitches, which I don't stock.

[RF]

Thanks to all for your efforts.

I have ordered Diode A ($16 incl shipping)and now I am waiting for the sparks to fly :-)