blew a psu. a little help repairing it please :)

[s e t h]

hello all

i blew a psu by switching on a system in a 230volt area while the psu was still set to 115volts
instant very load BANG and magic smoke resulted :D
stupid i know but never mind that :p:

i need a little help repairing it please

so i disassembles it to try and identify the fragged component.
the only thing that looks damaged is a small (squished sphere +-7mm diameter) M&M like orange component (with two legs) between the only two huge black capacitors on the board.
it was glued down very messily and unfortunately i scraped some of the identifying codes off it before i unsoldered it.

TVR 072*1 is all that's left
searching around i see there are numerous components available, with different numbers in the position i am unable to identify.
TVR 07271. TVR 07241. TVR 07221. TVR 07201 < those are all possible replacement parts as far as i can tell :(
so basically if anyone is able to help me feel safest about which one to aquire and solder into it's position i would be very greatful.

if anyone has the unit open and can see the component in question that would be best i guess (thermaltake 520watt power station)
(it was a gift ;) )

thanks for any and all assistence :cool:

[sluggo]

It's a Varistor, probably being used as a surge suppressor. It's designed to protect the rest of the supply by limiting current when a high voltage appears at the input. The impulse width that this device usually works on is in the .0001 second range, whereas your situation exposed it to many pulses in the .05 second range. It blows up in this situation, as you saw.

The parts are rated by the "2*1" field, where the 2* is the voltage, and the "1" is the number of zeros after the voltage. In your case, you would want an 07241 which means "7mm diameter, 240 Volt operation".

As far as the rest of the supply goes it's anyone's guess. If you replace the varistor and it blows again then you've got serious problems deeper in the supply and it's probably time to pitch it.

[s e t h]

hey sluggo :)
thanks for the response.
i have reinstalled a 07241 in place of the blown one.
a quick test didn't manage to fire up the unit iether on a dodgy board or jump starting it :(

i'll try again before i try and figure out what else got taken out.
btw do these varisters have polarity? i'm not sure i inserted it the right way round.
if they don't have polarity then i fear something else is dead too.
if so do you have any other ideas what i should be looking for or how to go about it?
might be time to strip this unit for spares soon :(

[sluggo]

hey sluggo :)
thanks for the response.
i have reinstalled a 07241 in place of the blown one.
a quick test didn't manage to fire up the unit iether on a dodgy board or jump starting it :(

i'll try again before i try and figure out what else got taken out.
btw do these varisters have polarity? i'm not sure i inserted it the right way round.
if they don't have polarity then i fear something else is dead too.
if so do you have any other ideas what i should be looking for or how to go about it?
might be time to strip this unit for spares soon :(
No, they're not polarized. Electrically, they look something like two zener diodes back-to-back. If you're replaced it you might try measuring the voltage across it to make sure you're not broken somewhere before that.

If you have AC on the varistor then you want to check the large caps and see what voltages you have on those. This is just a gross functionality check - there may well be other broken parts on either sire of the varistor (i'm assuming, based on its voltage rating, that it was being used on the AC side of the primary).

You don't need to connect the PSU to a motherboard. A 10 Ohm, 10 Watt resistor across +12 is enough to get the supply to regulate. Cheers.

[DeltZ]

internal fuse?

[zwawy]

s e t h

Now my question regarding a change of this piece ... will the PSU work again after you reinstall it ?

Thanks