Umm...Help, please? PSU just blew!

HopeAndDriftWood

Hi,
I bought a new Coolmaster case today, as my old computer was heating up quite fast.

I've been trying to install everything, and had some problems with getting it to work. It starts up for a few seconds, and then instantly cuts out. No error beeps. I got an old PSU and tried one fan, on an old motherboard, and it instantly blew and tripped the whole house. It wasn't connected to my motherboard, and the fan was working until then. I haven't tried it since.

The PSU is about 6 months old, and is powerful enough to supply the unit. I've installed everything on the motherboard according to exact manufacturers instructions, and can't see anything wrong with it.

Any idea what I can do?

fwor

This is sometimes caused by a short from the mobo to the case - the PSU detects over-current and shuts down.

Generally you can test for this by removing the fixing screws that hold it into the case and then simply resting it in the case on an insulator (I normally cut a piece of cardboard that is just larger than the board and tape it to the underside). If it boots up Ok like that, you know to look carefully for places where it may be contacting the metalwork,

CHR15

You did mount the motherboard on standoffs??

there are usually little brass standoffs which screw to the case, then the motherboard sits on the standoffs (the screws to hold the motherboard go through the mainboard and into the top of the standoffs.



Sometimes the standoffs can be plastic and the motherboard simply pushes onto them

HopeAndDriftWood

Oops
I'll go and use them on the motherboard...I've just found the little bag of them now.

Is it all still safe to use? Tech support said I'd probably blown the PSU if it wouldn't independently run a fan, but I definitely have only seen the old one blow, and the new one still powers the computer for a few seconds. If it makes a difference, the old PSU was only 250, whereas the new one is 700, and the old PSU has no on/off switch.

Thank you both

pendulum

SaucySecrets wrote: »

I've installed everything on the motherboard according to exact manufacturers instructions,

DOH!! :rotfl:

fwor

SaucySecrets wrote: »

Is it all still safe to use? Tech support said I'd probably blown the PSU if it wouldn't independently run a fan

Tech support are ~probably~ wrong. A fan will only place a load on the 12V output, and most PSUs will shut down if they find no load on the 5V outputs.

Please don't take this as any form of guarantee, but a good-quality PSU ~should~ have "crowbar" protection on the outputs which should stop it from damaging your mobo if it has internal problems. If it's a cheap and nasty one, all bets are off..

HopeAndDriftWood

Okay, so I changed the motherboard over, it's on the stand off thingys now. I left most things wired in, so I think it's all the same, but there is no response now. Nothing at all. It did trip the house last night, so I've tried a new plug, and a new kettle plug, but still nothing at all.

Should I go try to get PC World to test my PSU? Or am I looking at a new motherboard? I just really want the thing working now, it cost a fortune!

CHR15

Do you see any little lights on the motherboard when it's all plugged in but not switched on (PC switched on I mean)

If you have access to another PSU you could try that..

totalsolutions

Hi,
RE: Standoff's

You only use a brass standoff in a few carefully selected locations marked by a ring on the printed side of the board, normally 6. I hope you have not placed a standoff in every available, tapped hole on the chassis.

HopeAndDriftWood

Umm...if I have, is that really bad?

mongoose2009

what i would do is get another known good PSU

then just take out the mobo from the case and put it on a non conductive surface

formica counter top will be fine

then 24 pin plug in the psu and a monitor only into the mobo and short the 2 power connctions on the mobo (look in the mobo manual)

and see if you get boot to BIOS screen