Re: whacked by asploding transformer, part deux

"Ralph Mowery" <rmowery28146@xxxxxxxxxxxxx> wrote in
news:k7udnQ3qHawRwbLVnZ2dnUVZ_hKdnZ2d@xxxxxxxxxxxxx:


"Nate Nagel" <njnagel@xxxxxxxxxxxx> wrote in message
news:g0nj300gv@xxxxxxxxxxxxxxxxxxxx
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
.

Relevant Pages

  • Re: Does a MOV shunt current or equalize voltage?
    ... A MOV across a relay coil shunts nothing to ground and protects entirely by voltage limitation, absorbing the energy stored in the relay coil. ... For a service panel suppressor, with a MOV from hot to neutral/ground/earthing-electrode-, say a 10,000A surge arrives on a hot service wire. ...
    (sci.electronics.design)
  • Re: surge protection for cart
    ... a severe voltage spike from damaging your expensive gear. ... Power conditioning for consumer equipment is a different application. ... When the MOV on that branch ... Suppose the incoming surge is 1600 volts. ...
    (rec.arts.movies.production.sound)
  • Re: whacked by asploding transformer, part deux
    ... finally tore down my dishwasher today after getting sick of doing dishes ... replaced the surge strip and the TVSS breaker that was in my main panel ... MOV, is value important, or simply "bigger is better?" ... The mov is basically an open circuit and shorts out when a voltage higher ...
    (alt.home.repair)
  • Re: MOVs and surge suppressors
    ... I thought the only way to test a MOV was to send a surge ... and is this a way to test any MOV or MOV device? ... Plug-in suppressors have their current limited by the significant impedance of the branch circuit. ... protector was so grossly undersized as to be permanently destroyed. ...
    (sci.electronics.basics)
  • Re: MOVs and surge suppressors
    ... I thought the only way to test a MOV was to send a surge ... and is this a way to test any MOV or MOV device? ... They do not protect by absorbing surge energy, but in the process of protecting they absorb enengy. ... protector was so grossly undersized as to be permanently destroyed. ...
    (sci.electronics.basics)
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