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Old 09-12-2010, 08:05 PM
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kotofei kotofei is offline
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Broken microwave: bad magnetron?

Greetings everyone,

I post here since AK has many people familiar with principles of microwave emission.

My belowed home microwave oven, Samsung mt1066sb, broke today after 7 years of service. It doesn’t heat anything in the microwave mode, just make a strong buzzing sound which hasn’t been there before. All display functions work and the turntable rotates. The Samsung has built-in grills, they continue to heat and are controlled by timer as before; importantly, no buzzing sound is heard in the grill mode.

I opened the oven and didn’t see any gross damages, blackened parts or bad connections.

Since this oven works as a conventional grill (i.e. bake, broil etc) and only microwave “part’ is broken, I would like to fix it (especially if one takes into account that replacement is around $250 and is available only online).

Internet searches points at a faulty magnetron as the most likely source of this problem. Samsung magnetrons are available at epay (new) for around $50 and replacement looks pretty straightforward.

However, I don’t know what might be a reason for a magnetron going bad and how one can test magnetrons. Could it be that some component connected to the magnetron went bad and this cause the oven malfunction or killed the magnetron? I noticed a HUGE transformer inside the microwave oven which probably powers the magnetron; could it be shorted?

Any advices of those who changed magnetrons, diagnosed or fixed microwave ovens or just opinion on this subject is greatly appreciated.
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  #2  
Old 09-12-2010, 09:08 PM
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chillwolf chillwolf is offline
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If the the magnetron goes it usually doesn't make any noise when operating. Sounds more like the hi voltage transformer to me. To check the transformer for continuity you will need an electrical schematic of the system to see see what the values are supposed to be. Replacing a transformer is a fairly straight forward job in most microwave ovens, except for some of the over the range models. Just make sure to discharge the hi voltage capacitor before attempting any repairs! And make sure that you get your wires on the correct terminals on the transformer if you replace it. A lot of times the replacement transformer will not have it's terminals in the same exact location as the original one.
Most every failed magnetron that I checked as an appliance tech, usually had a hairline crack in one of the big magnets.
The loud buzzing sound is usually an indication of a failed hi voltage transformer.
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Last edited by chillwolf; 09-12-2010 at 09:11 PM.
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Old 09-12-2010, 10:10 PM
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kcollins4 kcollins4 is offline
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You mentioned info from the internet pointing you in this direction. Don;t know if you've looked, but Samsung might have troubleshooting charts for your MW. Many MW's have the service pack inside the unit, under a cover.
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Old 09-12-2010, 11:31 PM
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Might be the high voltage rectifier diode...I saw ten times as many diodes blow as I did Magnetrons, I started working on appliances back in the early '60's as my family has owned a major home appliance service agency since 1952....still own it, but business isn't what it used to be...

The strong buzzing sound is what is usually a tip off to me...

The diodes are fairly inexpensive, I'd take a multimeter to the one that's in your machine and see if that's it...it will conduct one way but not another...that is, if it's good...a bad one usually blows and shows infinite resistance....

good luck
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Last edited by RickB; 09-13-2010 at 11:06 AM.
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Old 09-13-2010, 11:01 AM
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I have a similar much beloved old microwave/convection oven and it has gone down 2-3 times since puchased in 1985. Each time the convection oven would work and the microwave would not. Surprisingly, each repair was cheap at the shop and simple. Bad interlock switch and wiring, safety switch alignment and electronic circuit board repalcement. The latter I thought would finish the unit off as so few were made. The tech located one and the cost was only $50 installed.
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Old 09-13-2010, 01:37 PM
markdi markdi is online now
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sounds like a bad diode to me
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