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Posted by Jim Yanik on May 17, 2008, 6:52 pm
>
>> Hi all,
>>
>> finally tore down my dishwasher today after getting sick of doing
>> dishes by hand and striking out on Craigslist. For those of you that
>> missed the first installment, a transformer exploded a couple streets
>> over late Sunday night or early Monday morning and blowed up some
>> stuff in my house (a surge strip, an electrostatic air filter, and my
>> dishwasher.) I've already ordered (online) a new power supply for the
>> air filter, and replaced the surge strip and the TVSS breaker that
>> was in my main panel (the "protected" light was out on one leg.)
>>
>> Turns out that the failure of the dishwasher looks exactly like the
>> failure of the air filter; on the power supply board there is a
>> orangeish-yellow dsc-shaped component soldered onto the board about
>> 1/2" in diameter, and it appears to have failed with extreme
>> prejudice. Am I correct in assuming that this is a MOV? Could I
>> just do a component level repair of this rather than replace the
>> whole board? I really hate this dishwasher and don't want to spend a
>> lot of money on it. If this is a MOV, is value important, or simply
>> "bigger is better?" I'm sorry for the dumb questions, but I'm not
>> particularly electronically knowledgeable (made it through two EE
>> classes in college and I think I've forgotten most of what I learned)
>> just trying to get this back up and running. If Trible's had still
>> been open by the time I got it apart, I probably wouldn't be asking
>> the question, but if there's a chance I could fix it today...
>>
>
> If it is the MOV, you can just cut it out of the circuit and try the
> washer.
Usually,there is a fuse inbetween the MOV and line source,so the fuse opens
whne the MOV shunts the surge/spike to ground. I've seen MOVs split
open,and PCB traces vaporize,and the power supply still work when the fuse
was replaced and trace repaired.
Sometimes the switcher transistor/FET gets blown,too.
> The mov is basically an open circuit and shorts out when a
> voltage higher than what it is rated for hits it, then opens back up
> when the voltage returns to normal. This is to protect the circuit
> board from voltage surges. If they get hit with too big of a surge
> they may blow off the board.
>
> If the washer works, feel free to use it, but replace the mov as soon
> as possiable incase you get another surge.
> You may want to unplug it or cut off the circuit breaker when it is
> not in use, especially if a storm is near.
>
> The bigger is beter is still in effect. Keep the voltage rating the
> same, but you can go up in the power rating.
>
>
>
>
MOVs usually are marked 130Vxx or 250Vxx,yours probably is a 130V MOV,and
they come in varying current sizes.
--
Jim Yanik
jyanik
at
kua.net
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