115v on PSU, whats the damage?

Durzel · 23 Oct 2006 at 10:52

I have a mate whos girlfriend thought it would be a good idea to change the voltage setting on the back of his PSU from 230V to 115V, with hilarious results.

He already knows the PSU is dead, but he hasn't been able to check anything else yet.

What's the likelihood that one or more things in his PC are now toast?

semi-pro waster · 23 Oct 2006 at 10:56

It really depends mainly on the quality of the PSU, if it is a decent PSU then the chances are fairly good that it will have died itself but kept the other components ok, if it was a cheap generic type thing then it is more likely that everything is shot(most probable components being motherboard, CPU, Ram and possibly the video card, the hard drives and opticals might be ok).

It is also possible that a poly-fuse has been tripped in the PSU and if he is very lucky then the PSU will be ok when the poly-fuse returns to normal(~24 hours or so) but that is a pretty long shot.

He should probably also consider telling the girlfriend that anything like that is her responsibility to pay for, there is no decent reason to be changing the voltage settings unless you are moving country.

Defcon5 · 23 Oct 2006 at 10:59

She probably thought it was to turn the psu off!

Durzel · 23 Oct 2006 at 11:05

I just asked him and he said that it cost him £10, "for 500W". So, prognosis isn't looking good.....

semi-pro waster · 23 Oct 2006 at 11:24

Durzel said:
I just asked him and he said that it cost him £10, "for 500W". So, prognosis isn't looking good.....

I don't particularly want to say it is all his own fault but..... If he does buy a cheap PSU and then allows his girlfriend to mess about with it I think he has at least partly brought this on himself.

I hope it is fine and that he is lucky but depending on the system I'd be suggesting strongly to him that ~£40-50 is where PSUs start being worthwhile over a generic fit it and hope.

BullBoyShoes · 23 Oct 2006 at 12:44

FYI, the 230-115v switch is a voltage doubler, so by setting to 115 and applying 230v, the PSU will see ~460v, blowing the **** out of it!

paradigm · 23 Oct 2006 at 13:10

BullBoyShoes said:
FYI, the 230-115v switch is a voltage doubler, so by setting to 115 and applying 230v, the PSU will see ~460v, blowing the **** out of it!

Voltage doubler :confused:

care to run that one by me again?

The PSU CANNOT see 460v, the main ring is only providing 230V AC to the plug. That switch just changes the input values, and hence uses different amounts of transformer coils to generate the needed 12v, 5v, 3.3v etc etc from 115v or 230v. All the switch effectively did in this case was possibly provide UP TO 24v on the 12v rails, but most likely actually blew the main fuse BEFORE the rails.

IMO the prognosis should be (regardless of PSU quality) that the only dead component is the PSU (and possibly fuse in the kettle lead).

Durzel · 23 Oct 2006 at 13:20

Cheers lads, will update thread when I find out more

BullBoyShoes · 23 Oct 2006 at 13:21

Yes youre right, the mains voltage is 230v, but internal to the PSU (and this is just one way of doing it) there will be a voltage doubler circuit.
So if your in the UK, set the switch to 230v, effectively disabling the doubler. If your in a 115v country, flick the switch to enable the doubler. either way the voltage the PSU will "see" is 230v. This way multiple transfomrer windings are not neccesary.

ReeMISM · 23 Oct 2006 at 16:04

I know someone who did this with a cheap psu and it was just the psu that went everything else was ok..

SteveOBHave · 23 Oct 2006 at 16:11

I used to do production line PC builds and if a cheap PSU goes, it's generally gone...

Back in New Zealand when I was just getting into the PC thing, I was building all the super market PCs for the checkouts in the North Island. You couldn't actually see the voltage settings as they were totally enclosed in the case and inevitably 3-4 out of 20 would be at 115V. We'd plug them all in to a mains switch and then power the lot up at once and get these lovely little puffs of gray smoke as the PSUs went up!

It's a red switch for a reason LOL.

Dr.EM · 23 Oct 2006 at 16:19

Unlucky

. Someone did this on a school computer and it toasted the whole thing. Undoubtebly it was a very cheap PSU in the machine. So glad they have automatic selection on most now, those switches terrify me :eek:

Durzel · 27 Oct 2006 at 13:32

An update for anyone who needs closure...

He replaced the PSU and everything else was fine. I guess it just instantly died before it could have a chance to apply power to anything else.

Darg · 27 Oct 2006 at 14:27

Good news. It would have been bad for that relationship if she'd blown up his entire computer

rangor gubbins · 27 Oct 2006 at 16:28

Durzel said:
I have a mate whos girlfriend thought it would be a good idea to change the voltage setting on the back of his PSU from 230V to 115V, with hilarious results.

lol. very unfortunate. but made me laugh.

Glad it all worked out ok

Rroff · 27 Oct 2006 at 19:08

Would have thought in this day and age, hell even a few years ago, all PSUs would have been able to shutdown gracefully with the wrong voltage, without any damage, not like it a hard thing to implement... and I know a few PSUs that do have protection against it...

Watts / Amps = Volts so you can get 110 to 240 at the expense of one of the others...