PC won't power on.... help please!

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-Acid-

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AmiBayer
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This morning I got up and switched my pc on and went ot make breakfast as usual. When I got back to the computer 10 minutes later it was switched off. Unusual I thought so tried to turn it back on and it wouldn't. I had a look round the back all cables were in place so I switched the PSU off and then back on using it's on/off switch and tried to turn the pc back on again.

This time it booted up to windows normally so I went to check the weather and the system suddenly powered down (2 minutes from switching on to powered down). No warning whatsoever.

Now i'm back in from work and trying to figure it out but when I hit the power on button nothing happens, turning the psu on/off does nothing. The orange on light is lit up on the psu and when attempting to power on the first time when I came in from work (I had the case open to check fans were moving) the system fan moved a few mm but nothing else is happening.

Before I dismantle my backup pc, does this sound like the PSU has had it? (Only bought it about 5 month ago). The system has in it a Gigabyte mainboard, iCore5 3750K cpu, 16gb ram, 3 sata hard drives, dvd writer and a HD Colossus video capture card.

The PSU is a Power Cool PC-450AUBA-B (450w), i'm using the graphics card on the cpu by the way. This has worked flawlessly since I bought and built the pc last November (roughly) and I have not changed any hardware or software lately.

Any idea's?
 
You can test the PSU on another motherboard. If you want to avoid that, short the PS_ON pin (green wire) to a GND pin (black wire) e.g. with a bent paperclip. Then measure voltages etc according to the ATX plug pinout.

Check for failing caps too, especially around the CPU. Just today I repaired a dead motherboard (no life at all upon powerup) at school, 7 out of the 9 caps around the CPU had miserably failed with exploded bottoms. They were miniature 680uF 4V ones, suitable for placement under the Intel heatsink and apparently also very suitable for suicidal behaviour.
 
Sounds like its overheating to me. During my time as an IT repair tech, I've come across a number of systems (particularly P4s) that do this. Upon inspection they had no thermal grease whatsoever left between the CPU and heatsink as it had all dried up.

This would be my first thing to check based on experience, particularly if it comes back on afterwards (as it would have cooled down a bit).

EDIT: Having read the rest of your post :picard (I'm sorry my eyes are becoming lazy lately as I'm overworking myself and my head isnt working properly either) I would be trying a new PSU. It may be possible something somewhere has shorted. But it may not necessarily have been inside the PSU. Cheap PSU's I've dealt with in the past have had a habit of taking other components with them when they die. Hopefully, this isn't the case here.

If you can verify the PSU is okay, either by getting same result with a known working one or using it n another system, I'd be inspecting the motherboard as BLTCON0 has suggested. Look for signs of bulging caps and shorts. Give it a good sniff too. Most things that short leave a feint smoldering scent.

If neither of the above work, I'd probably try another CPU but you should be getting a POST beep if it was just the CPU.
 
Also, unplug the power lead, yank the battery for 10-20 secs and and plug it back in and see if clearing the bios helps it out. (Looking at you stupid Dell OptiPlex 780 models that I support at work)
 
Gouldin said:
Also, unplug the power lead, yank the battery for 10-20 secs and and plug it back in and see if clearing the bios helps it out. (Looking at you stupid Dell OptiPlex 780 models that I support at work)
Click to expand...

Ah, CMOS reset! That is also worth trying. :thumbsup:
 
I would say the PSU at 450watts I would say it is not enough juice and has gone pop......Overheating of the CPU or Graphics Card could be the issue if the system goes into shutdown straight after booting
 
450watts should be ample on that setup. There's no gfx card to suck too much power, somshould be well within limits.

I'm using a corsair cxm500 with a core i7 3770k and gtx660 gfx card no probs
 
I would say when turning on, the fan turning half a millimetre indicates that the PSU has bitten the bullet. With the CPU you are using, three SATA hard drives and DVDRom, it sounds like 450Watt wasn't enough. :o
I personally (although with a discrete graphics card of decent spec) would go for something like a Corsair SX620. (they look sexy too, in a kind of weird 'Techie' way.
 
thats why i posted to get the cxm500 or cx500 but a decent branded one is safer

i use a hx520 with a 2500k and gtx660 fine
 
In my main machine, I use an TX1200 - It's a bit overkill, but with an Obsidian D800, 2x7990 ATI Graphics cards, 5 Hard drives, 2 DVD Writers, 1 BluRay Writer, a 990X installed in a Rampage Extreme III, oh and 12Gb RAM (Dominator 2000Mhz) and H100 closed water loop, you can't be too careful about power. :lol:
I prefer PSU's to have a large 12 Volt rail. ;)
Anyone would think I was sponsored by Corsair.. ;)
 
In a minute i will take the psu from this pc to try in my main pc. This one had a higher rating but i'd had it since 2007 (I think this one is a 600 or 650watt) so bought a new one.

It annoys me that I asked overclockers.co.uk if the psu was suitable and they said it was, so bought it based on that advice along with the board, cpu and ram all at the same time.

Well off to see how this goes anyway....
 
If your PSU is only 6 months old, can you contact Overclockers UK and create an RMA, surely it's still under warranty (1 year)?
I bought all my kit as above from them, and they are usually really good.
I guess at the end of the day, they are sales guys and any advise given would be subject to your own personal choices. (and available funds too)
 
Your PSU should be sufficient for your setup (run your system through a power monitor and it is surprising how little a modern system will use unless you have a monster GFX card or mega overclock) - you do need to isolate the problem though.

I would always recommend isolating/eliminating each component and re-seating everything first as it can often be down to something not quite sitting properly...

Pull out all the SATA cables from the drives, all fans except the CPU cooler, re-seat all connectors from the PSU to motherboard and re-seat each memory module. Also then try booting without any RAM to see if you get any POST beeps but the system/PSU staying on.

If the motherboard has onboard VGA remove the GFX card as well, including any additional cards. If after all that(!), you need to either isolate the PSU by testing on another board and hopefully you have then narrowed it down to either the PSU or motherboard/processor (although much less likely to be the processor these days unless seriously overclocked).

One last thing worth doing on all desktop PCs anyway is to clear out any dust that has accumulated using an air-duster can of air across all connectors, slots etc...it also keeps the fans spinning nicely and quietly...

And of course a CMOS reset (battery pull/jumper to reset) will also eliminate any bad BIOS config/overclock settings (although unlikely for you unless you were on a high overclock).

Hope you manage to find the source of the problem! :)
 
Thanks for all the suggestions. I got the pc open and it was very clean still surprisingly dust free even the fans (i put the hoover over it anyway just to make sure).

Anyway to cut a long story short there was a singed smell as soon as I got the side off and it was definitely coming from the psu. Board and components all looking in pristine order like the day I installed them. Caps all look good, everything normal it seems.

Got the psu out and had a good smell, got someone else's opinion and they agreed something was burnt. Decided to break the seal and open it. Inside on one of the coils, the copper is broken and some parts of it have turned black and a plastic strip that was inbetween a heatsink and the mentioned copper coil has been melted and is now glued to the burnt out copper coil.

I'm no electrician but I think I can confidently say the psu is fried (aka knackered). Anyone disagree? I'm going to buy a new one locally tomorrow instead of pulling this pc apart, at some stage I will be adding a top end graphics card, what wattage power supply would you suggest I get? how many rails etc is needed?
 
Hi there,
Johnim has posted links to a good reliable PSU, depending on your graphics card choice, anf for future proofing, you could look at scan for a 600Watt PSU,
It's your choice, but for cable management, you might want to look at a modular PSU.
As stated before by Johnim, just be careful of cheap ones that look a bargain.
 
Most modern systems wont use more than 400w, unless it has multiple top end graphics in it but you need some head room to stop the PSU from straining.

Without a dedicated graphics card you're probably looking at 160w - 220w actual usage.

Here's how I work out my systems. The quoted figures are estimates based on averages for the components and in some cases a little generous headroom to compensate for variance between models.

2nd / 3rd gen i5 CPU 95w OR i3 65w (AMDs usually have equivalents but some can be 125w)

Motherboard 40w
RAM 10w per stick
Hard Drive 15w
Optical Drive 15w
fans I allow 10w for all

A nice low power ATI 7750 would only consume 75w additional. Some beasty graphics can go up to 210w.


With PSU's you'll want to allow about 100w headroom minimum to keep them from stressing. You can assume most to run at around 70 - 75% quoted efficiency long term unless you pay for an 80% certified one.
This means a cheap 500w PSU shouldn't really be running anything that sucks more than 375w long term. But sounds like you're way clear of that. Still, cheaper PSU's aren't as reliable.
 
When a system refused to boot and the fans just move a very short distance it is always the PSU... but be prepared as it might have also taken the motherboard with it. When a system refuses to boot and you know nothing is wrong, try not to keep testing it by power cycling the PSU/system as a PSU on its way out can easily take the motherboard and sometimes more components with it.

You really shouldn't have opened the PSU as you have now voided the warranty and won't be able to get an RMA refund/replacement. All items in the UK must carry a 1 year warranty, so it was definitely covered, however most PSUs will have a 3-5 year warranty.

Regarding PSU ratings. Definitely don't run one only just large enough for your system requirements as it will be stressing it. I would never run a current system on anything smaller than 500W, regardless of spec, because HDD's especially stress the PSU at boot time, and although a CPU will idle with just 15-20W usage, when under stress most will go to 90W and more. The larger the PSU the more headroom you will have, and a more stable system too.
 
Has anyone even looked at the 12V output for that PSU? It's easy saying 450W is plenty, but it's not just the wattage that counts. That PSU has a pair of very weak 12V rails rated at just 8A and 13A... I doubt it can even manage 450W to be honest and i'm pretty certain the PSU is the problem (lets just hope it hasn't damaged the motherboard etc...).


EDIT: I'd recommend this XFX PSU for the price/quality (it's a Seasonic unit):

http://www.overclockers.co.uk/showproduct.php?prodid=CA-007-XF&groupid=701&catid=123&subcat=2463

It comes with a 5 year warranty and will provide enough grunt for a decent mid-high end GPU if you ever decide to upgrade :thumbsup:.
 
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