27 replies to this topic

[Jammy]

Had turned it on for a few minutes this evening, then out of no where there was this loud bang, the monitor switches to standby immediately and one of the breakers in the house flips. Then a small whiff of smoke eminates from the tower for a few seconds.

Nothing was on fire, so I quickly take the CPU fan off to make sure the processor hasn't blown, it looks fine. The rest of the MB looks fine too, no capacitors gone or anything, next idea is to check the graphics card. Take it out the tower, take the cooling fan off, I notice some scortching of some thin rectangular bits of solder, but nothing apart from that. One thing I did notice was that, of the two feeds from the PSU, one of the yellow wires that goes into the Molex had come out (tis one yellow wire graphics card side, two yellow PSU side).

I clean the dust from the CPU fan, re-attach it, re-insert the loose wire from the Molex and plug everything back together.

I press the on button on the front of the case, and the fan spins up for a fraction of a second and then the power cuts out, do this a couple more times before it all powers up fine.

Have now been using it for a good 30-45 minutes and it seems absolutely fine? Was it just that yellow wire shorting out against something?

[Ethel]

It's only 5 or 12 volts so don't think it'd bang. More likely if it stopped a cooling fan from working that it shut itself down to avoid overheating.

Edited by Ethel, 27 November 2007 - 10:26 PM.

[Bungle]

what size is the fuse in the plug

its unusual for something with as small a load as a computer to trip a circuit breaker

[mini93]

yes its going to blow up, throw it out the window before it explosivos!!

[yorkshirechris]

explosivos!!

Is that spanish for Explodes?

[mini93]

its Tenacious D for expolode i think

[Silicon Skum]

It's only 5 or 12 volts so don't think it'd bang. More likely if it stopped a cooling fan from working that it shut itself down to avoid overheating.

Yellow wires on a computer PSU are 12V lines.



Jammy, if you heard a definite "BANG" then it was likely to have been a capacitor inside the PSU. Don't attempt to open it if you don't know about switchmode PSUs and safely discharging capacitors - they hold a large charge for quite a while. Very probably that the noise may also have been from the loose 12V wire touching ground (any part of the case, and certain parts of the circuits) and shorting out - which also is very bad for the PSU....and prolly damaged it.

If you have any hardware monitoring software (temp, voltages, fan speed etc.) check the voltages are within range - if not then restart the computer and go into the BIOS and look under the "hardware monitoring" / "system monitor" tab of th BIOS and check the voltages:

System voltages should be within these ranges.

12V - 11.98 - 12.5

5V - 4.89 - 5.3

3.3v - 3.1 - 3.4

-5V - -4.89 - -5.3

-12v - -11.98 - -12.4

CPU - depends on cpu - check against the manufacturing spec sheets on Intel or AMD websites

Ram - DDR 2.5V - 2.6V, DDR II 1.8V - 1.9V

If any of the voltages are out, then ther is either a fault with the PSU, or possibly the VRMs of the motherboard - depending on which voltages are out of spec.


It's unusual for the PSU to trip a breaker on the fuse box, unless there is an internal earth fault. Mind you it *could* also have been caused by a power surge on the mains - which is also bad for the PSU.

Give it a good check over to make sure it's all happy, before continuing to use it.

SS

[nev_payne]

For safteys' sake back up everything.... ASAP.

Bang could be PSU or the graphics card.. if you want to continue using the PC, anything suspected of blowing a resistor or cap should be replaced.

Silicons got the right idea on checking the volt levels.

Hope it doesnt end up becoming overly expensive for you.

[Jammy]

*Blissfully ignorant mode* I'm sure it'll be fine!

I'll go check the voltages and go from there!

Thanks people.

[Amy]

Nightmare! I hope it's Ok Jammy, we lost our PC a few weeks ago.....

I'm soooo glad we bought a surge protector for the new one, we had four power cuts within a two minute gap this morning, but the little UPS is working a treat- phew!!

Good luck sorting it out.....

[Matt]

if you heard a bang and a little puff of smoke... then something melted or burned.

the yellow wire as loads of people have pointed out is a 12v feed.
and that you found it had slightly scorched the graphics card is nothing to really worry about..

i would be checking the volts and as a precaution getting a new psu anyway...

but id give it a go for a few hours running some games to see if you've cooked your graphics card.
only time ive ever made a pc bang was discovering the switch on the back of the psu 110 - 240v..

and switching it to 110

all good fun!

[Silicon Skum]

only time ive ever made a pc bang was discovering the switch on the back of the psu 110 - 240v..

and switching it to 110

all good fun!

Heheh, I blew up a whole PSU by pulling WAY too much current on the 12V lines (was powering a stack of thermoelectric coolers) - the switching regulators blew apart, and the rest of the PSU shorted out. There was a huge blue flame like flash that flew out of the PSU's air vents. Was quite impressive!

Sadly a few days later the computer (now on a new PSU) started acting a bit strange, and the motherboard died - and took the CPU and RAM with it!

SS

[Bungle]

*Blissfully ignorant mode* I'm sure it'll be fine!

I'll go check the voltages and go from there!

Thanks people.

go check the fuse size in the plug as well

[Miniman]

only time ive ever made a pc bang was discovering the switch on the back of the psu 110 - 240v..

and switching it to 110

all good fun!

Same. its all good fun

[Dom]

*Blissfully ignorant mode* I'm sure it'll be fine!

I'll go check the voltages and go from there!

Thanks people.

Make sure you back up all your files. In case anything does happen.