One for the 'lectrically minded boffins...

[GSwadd]

Now I know computers but my home pc has fried another power supply and that makes 4 in as many months now After the first went I changed my old powerboard for a new surge and overload protected one thinking it might be dodgy. New power supply in and it lasted about 6 weeks then went pop again when one of my lads turned it on one morning. Put it down to bad luck and replaced it again and it went fizzle one day when the pc wasn't even turned on. Power was on at the board but pc not running. This was replaced again and that one went last Saturday when being turned on again, lasting a few weeks. The final one I put in Saturday morning lasted until Monday when it too smoked up while the pc was off. Now I get my boys every second weekend and that's when it always seems to go. I can use it for weeks myself with no problem. Additional items plugged into the circuit are a tv and PS2 which were on at the times the power supply fried. They are on the same circuit but not plugged into the same powerboard. I can understand surges and spikes when turning on the pc but how can it fry 2 now when it is turned off? I know the soft start button allows power to the motherboard initially but couldn't see it allowing enough to fry something inside. Any ideas on what's happening before I replace it again? Will be plugging it into a UPS this time too.

 

[centaur]

Have you checked that the power supply is adequate for your pc ?

If you have added a lot of ancillaries, it may be asking too much of a low output psu....you may need to upgrade to something 'beefier'....and therefore, expensive.

You might also just want to check inside the PC's case to ensure there are no loose/dangling wires or ather metallic bits which could short-out the supply.

 

[GSwadd]

Checked al lthat 100 times. All power supplies have been 450 watt jobbies. Just opened up the last one and found it has a fuse that has blown. Glass has shattered completely so guessing it had some amps through it. I will unsolder it and replace it and see if it works again. Running now on a temp power supply through a good UPS.

 

[Colban]

When you say you have a TV and a PS2 plugged in,i presume you mean into a wall AC outlet.
You also say that the problem mainly occurs when the boys use it.
Are they being sensible or are they "playing".
A 450watt PSU should be up to the job,but it all depends on what it has to power.
You say you replaced a blown fuse.Was it input (AC) or output (DC) volts.
It smells like excessive current draw somewhere.Do you have any other symptoms?.Noisy fans,odd overheating problems,noisy hard-drive.
Can you go to a minimum configuration.Ie remove all but one memory card,graphics,sound cards.Run for a while and then add one component at a time.Intermittent problems can be a bitch to cure,but if you can repair the PSU with a fuse,you should be aiming to be able to get a reproducable failure that can be diagnosed by removing individual boards and monitoring the system.If it stops falling over with a particular card removed-replace that item.
Oh yes,good luck.

 

[redcastle]

If you have added a lot of ancillaries, it may be asking too much of a low output psu....you may need to upgrade to something 'beefier'....and therefore, expensive.

Cant be that centaur, even the cheapest nastiest chinese psu's have an overload nowadays so the machine would just close down if you called more power than it could give.

The machine being off but being plugged in is a great clue. There is certainly a short in the case.

The first port of call for me would be the mobo stand offs, the power switch and the reset switch. After that your down to other components that are drawing power independantly from the psu. CD drives, hard drives , flppy drives etc.

horrible to fault find and fix though

 

[centaur]

Cant be that centaur, even the cheapest nastiest chinese psu's have an overload nowadays so the machine would just close down if you called more power than it could give.

The machine being off but being plugged in is a great clue. There is certainly a short in the case.

The first port of call for me would be the mobo stand offs, the power switch and the reset switch. After that your down to other components that are drawing power independantly from the psu. CD drives, hard drives , flppy drives etc.

horrible to fault find and fix though

Yeah, I agree with you there...the on/off and reset usually aren't visible until you take off the panel they're attached by.
Sometimes, you can see minute evidence of burning on a graphics/sound card if they are faulty.

 

[GSwadd]

The machine being off but being plugged in is a great clue. There is certainly a short in the case.

The first port of call for me would be the mobo stand offs, the power switch and the reset switch. After that your down to other components that are drawing power independantly from the psu. CD drives, hard drives , flppy drives etc.

horrible to fault find and fix though

Correct me if I'm wrong but if the pc is off, ie: power to PSU but motherboard not active, then the only circuit drawing power would be one to the soft start switch? Suspected the switch as I have had some go before on old pc's where they took the brunt of the start-up surge. Other cards wouldn't get powered up until the motherboard became fully active? On a soft start system wouldn't it just be like a relay where it doesn't take all the voltage? As the tv and PS2 have been on both times (same wall ac outlet) could one of them be playing up and causing surges back through the power circuit? If possible you would think they would show some symptoms as well. Mind you a mate did have the same model LG tv catch fire at his home a few months ago

 

[redcastle]

No, thats not right. The power switch on the computer draws power from the motherboard via the psu so the motherboard and all other devices, CD , HDD are live and just waiting to be switched.

Been as you narrowly beat us at the cricket theres an easy way to demonstrate it. Remove the CD rom power cable and put your tongue (nice and wet) across the four cables...................

I doubt very much its one of the pci or agp cards connected to the motherboard and would look at devices connected by cable directly to the psu, hence the suggestion to check the mobo stand offs. Also check you havent got the spare leads from the psu tucked away somewhere thats shorting them to the case.

The playstation and TV are a tangent chum. If they were doing some weird back syphonage type thing then one of those would have blown too.

 

[GSwadd]

Been as you narrowly beat us at the cricket theres an easy way to demonstrate it. Remove the CD rom power cable and put your tongue (nice and wet) across the four cables...................

Think I'll decline on the little test...we have enough ashes in Australia now

Will look towards my cd-rom drives methinks.

Thanks.

 

[GSwadd]

Just an update guys....

All indications point towards a faulty soft-start switch now. I was fiddling inside the pc the other day and turned power on at the wall and the pc burst to life so I thought, thats ok, as some do that when first powered up (IBM's especially). After about 3 seconds of the post it shut off....then powered up again. If I had have left it it would have kept going through this power up/down cycle until something blew....namely the power supply! Explains why it only happened when the kids were by themselves, as I only noticed it myself cause I had the cover off and could see my nice blue led fan at the back turning on and off. The eldest lad did say he saw a blue flash last time it went....

Thanks for all the help folks.....

 

[Fanum]

Re-case it

Decent cases inc PSU are less than 50 quid now.....an hour of rebuilding and it'll be done and it'll look new and shineeeee

 

[bikermike]

Maplins are selling a tower/400W PSU/ keyboard / optical scrolling mouse /speakers for £25 or therabouts Just fitted an old motherboard, CD, etc, into one for my parents...looks OK too, nicely finished.