View Full Version : PC PSU issue

5th August 2009, 18:56
A friend dropped off his PC for me to look at because he couldn't get it to boot. From his description I thought it was a software fault that might just require repair or re-installation of Windows XP. However on plugging it in to the mains and switching the PSUs switch on the system fans started to spin up (very much like they were doing on the PC I build myself earlier this year).

The PSU in this PC is a Thermaltake TR2-500W unit and the PC is just over 3 years old. I originally built the PC for him so know it was put together properly originally and has been working fine until now.

The PSU has a status LED on the back next to the on/off switch. When power is switched on at the wall the PSU is jumping straight to Green, showing an on status and not the orange standby status it should be doing, and all system fans (including CPU, GPU, northbridge and case) are spinning up but the system doesn't start to boot. On pressing the soft power on button on the front of the case nothing happens. I can't get the system to boot at all. The HDD is spun up and power is going to the Motherboard as it's green light is lit.

Does this therefore point directly to a PSU failure? I sadly don't have a spare PSU to try and test this at the moment, other than pulling one from one of my working PCs, I would need to buy a replacement before I know for sure.

Question. If a PSU is on its own out of the case and connected directly to the mains power and switched on, am I right in thinking it should always remain off with no internal fans spinning unless I short the green/black soft on pins on the motherboard connector?

I've also read in a few places that powering up a PSU on its own by shorting the soft on pins can damage some PSUs because they need to be connected to some hardware that draws some power. Is there any evidence of this being true? I've been doing this since forever and not killed a PSU this way. Anyone know?

5th August 2009, 19:27
yo buddy,
i just googled this PSU for you and it seems to be a common fault (same symptoms) so bang a new PSU in there and away you go :thumbsup:

actually 3 years seems to be a good innings for one of those, most people are claiming about 9 months before it poos itself

cheers, JuvUK

6th August 2009, 00:14
Another kick test: short the green wire with one of the ground wires with the computer completely assembled: if the computer boots OK, can be a problem on a TTL latch on the motherboard (hard to spot since normally inside the south bridge).

6th August 2009, 01:10
Thanks. I will test that.

I have a feeling it is the PSU though, and after opening up the case I'm surprised the system lasted as long as it did before something failed. The amount of dust build up inside the case was worse than I've seen in a long time. The front 12cm case fan was completely caked in dust and the mesh dust filter in front of it was so bad there was no way any air was being let in. I don't think the owner cleaned that filter once since I built it for him!

I often see very bad builds up of dust in PCs I repair. It has to be one of the contributing factors to component failure. I tend to clean the insides of my PCs about once a month with a soft artists brush and the hoover nozzle held just above catching the dust as it is brushed. Keeps everything as new and allows the air to flow. How often does everyone else here clean their PCs? Inside or even just the outside and air intake grills?

6th August 2009, 01:51

I found a 500W PSU in the cupboard and so have just connected it up to the system and it booted first time, so it is definitely the PSU.

Have now discovered that XP won't boot completely. Gets past the account selection screen but then freezes while loading the desktop, so obviously something got scrambled when the PSU failed during use. So that will need fixing too. But at least the PC is working and it isn't anything more serious such as the motherboard, ram or CPU. :)

6th August 2009, 09:43

I couldn't agree more about the dust buildup issue.

I have had to replace three Core2Duo CPU's in clients machines in the last 8mths due to this problem. The CPU Cooling Fan's have been so caked with filth that they couldn't even move & the Heatsink fins where totally filled, ie heat preserving insulation applied :lol:
I make a point of cleaning my system out completely at least ecery 3 months.

Glad you sorted the PC out, I've got one here at the moment that twitches the fans when you apply AC power & that's it .... :whistle:

TC :mrgreen:

Kin Hell
6th August 2009, 11:17
Dust is a killer, for sure. Pet hair conpounds the problem & just gags to burst into flames.


6th August 2009, 14:34
Pet hair definitely is a nightmare. Especially cat hair as it is so light and floats around, gathering in balls of fluff that then clogs up with more dust.

at the moment that twitches the fans when you apply AC power & that's it

From previous experience that is normally a dead motherboard. I've had 3 systems to repair since April like that and they were all dead motherboard.

Is it that motherboards and other PC components are not as well built and fail much more than they used to? Or is it because they are much more complex now than before that there is more to go wrong? At least now they are realising the bad capacitor issue and are starting to use solid-state capacitors, so at least that solves the leaking issue.

Years ago PCs didn't seen to fail this much. My old systems from before 2003 still have their original motherboards and PSUs and continues to work. But any made after this seem to fail at some point. PSUs and Motherboards seem to be the weak components these days, with ram, cpu's and hdd's seeming to continue working fine, which is a turn around as those were the components that used to fail most often.

BTW, could Sold-state Capacitors be used for Cap replacement on Amiga motherboards?

6th August 2009, 15:20
Can anyone recommend some PSUs to look at under 50?

I spotted a OCZ StealthXStream 400W PSU for just 29.82. Is that any good?

I think 400W might be enough. The system spec isn't high. It's:

Athlon 64 3200+
Asus A8N-E MoBo
1GB PC3200 RAM
nVidia XFX 7600 GT 256MB GPU
1 internal USB memory card reader

I ran this spec through the Thermaltake power supply calculator (http://www.thermaltake.outervision.com/Power) and it returned 241W.

6th August 2009, 18:38
BTW, could Sold-state Capacitors be used for Cap replacement on Amiga motherboards?

Yes, they shall be used if the space between leads is the same.

BTW: I have an old board which wasn't start any more (same behaviour: just trying to start the fans). I swapped three bulged capacitors, measured the mobo voltages and flick the PSU on: it lives again!

Other regular cause of "dead" mobos are some of the voltage regulators going south. A bit harder to replace and spot, but doable. Only boards where the south or north bridge bit the bullet aren't fixable.

Kin Hell
6th August 2009, 23:07
@ Harrison

Yeah m8y. That OCZ StealthXStream 400W PSU should be fine. They had a few PSU issues in their earlier days, but they are okay now. OCZ actually bought PCP&C PSU company. They still ship the PCP&C PSU's under their original name. A 1.2KW affair will set you back a cool 352 but give you 90 Amps on a Single Rail. :blink: Jhat's sho sewiously oarshum, meh typin' is fubaR. 8)


7th August 2009, 01:31
90A on a single rail? For +12V that would give you 1080W :o does anything currently need that?

7th August 2009, 06:41
On the 90A question, yes there are video cards that use that much power. Now, you have to use multiple cards at the same time, but a current Radeon HD4870 consumes 20-25A all my it's lonesome! NVidia cards eat a little less if I remember correctly, and NVidia is pushing Tri-SLI. At 25A a piece, you quickly eat up that 90A and you have to have some headroom for the other components that pull from the 12V Rail. So, anyone else think something needs to be done about Power consumption?


7th August 2009, 17:41
It's a catch 22 situation. We are all demanding better quality graphics, faster processing, more ram, more storage etc.. but we don't want to be using more power to run it. The solution only comes with time as they optimise newer technologies and chip designs to be more efficient, use smaller die processes and run on lower power needs. But as we are always demanding more they never have time to optimise, but instead to push forever higher and faster.

The thing the computer industry really needs to look into is energy conservation. At the moment anyone building PCs will be worried about temperatures of components and having enough cooling to keep them safe. We have fans sucking in cool air, fans extracting hot air and blowing it out into the room, we have water cooling solutions which dissipate their heat using radiators and fans.. etc. But has anyone thought what a waste of energy this is? All this heat being generated is just being extracted from the system and dumped out into the surrounding air. In the winter is is OK as it saves on heating bills, but in the summer it just makes things even hotter. Surely there is some way we could utilise all this generated heat for something useful? Not sure what though. Any suggestions?

Kin Hell
8th August 2009, 17:03
<snip> there is some way we could utilise all this generated heat for something useful? Not sure what though. Any suggestions?

Staying warm? - 'Slovely & toasty by my feet with the SLI 295GTX roaring away. :coffee:


8th August 2009, 17:54
A toaster oven? Coffee mug heater? Infinite possibilities.

10th August 2009, 19:02

I thought I had this PC all ready to hand back to the guy today, but I tried to boot it up this morning and it isn't behaving. It is now refusing to boot. And I've tried it with 2 different PSUs today. The new one and the other one I originally tested it with.

Now when you switch it on from the wall socket the system is spinning up without turning it on from the case, but is pulsing on and off every couple of seconds, with the HDD and power lights on the case, USB mouse and keyboard lights, plus the system and CPU fans all doing the same, on, off, on, off etc...

Is the motherboard screwed?

When I get time later tonight I'm going to strip it right down, but as it isn't even reaching the beep at turn on or showing anything on the monitor I think it has to be the motherboard. And the PSU can now be ruled out as that is new.

10th August 2009, 19:37
sound familiar?

http://www.techsupportforum.com/hardwar ... lsing.html (http://www.techsupportforum.com/hardware-support/motherboards-bios-cpu/364139-computer-does-not-start-power-pulsing.html)

11th August 2009, 01:38
I found that page earlier. Shame the original poster hasn't followed up at the end of the topic with the outcome to his problem so we could see a conclusion.

I expect the motherboard is faulty as the PC has been doing strange things since I received it to look at. When I first tried to boot it with the old PSU all the fans just spun up and nothing else. With a different PSU the fans also span up as soon as the PSU received power, and the system took a few tries to get it to boot. Although it did boot and once it had it worked fine and rebooted fine. Only after hard resets would it be troublesome to boot. But now it is just pulsing on and off every couple of seconds with nothing else happening.

I'm going to reset the cmos and replace the battery and see if that helps. Fingers crossed as that would be brilliant.

11th August 2009, 04:18
Look carefully on the electrolytic capacitors, the fault can lay on those buggers. If no avail, time to replace the mobo.

11th August 2009, 04:50
I took the motherboard out of the system and hooked it up with just the PSU, CPU, 1 stick of RAM, and the graphics card and it did the same. As soon as you give the PSU power the motherboard starts to pulse. I also noticed the green led on the motherboard flickers so that must mean it can't be regulating the power properly. I expect it is a bad cap, but they all look perfectly fine when I examined the board.

So it looks like the board has had it.

My options now are to source a second hand AMD 939 motherboard from ebay or elsewhere at a reasonable price, but being second-hand there is no guarantee how long it would last. Or buy a new replacement ASRock board (only 939 board still made), or alternatively see if the owner is interested in upgrading to a newer CPU for slightly more money.

Now he isn't a power user and I could build him a newer system using a E5200, 2GB DDR2 ram and motherboard for 109, whereas the replacement ASRock 939 motherboard would cost 65 on its own. So maybe an upgrade would be worth it for the extra 44.

11th August 2009, 20:18
As I stated in the other thread I come across them fairly frequently, and if I find one, I'll let you know. I would, if I was in your shoes, suggest that the friend upgrades his computer, especially since it isn't much more than the replacement cost. With a newer mobo, it could make it easier for him to upgrade in the future.


12th August 2009, 13:36
Exactly what I was thinking, and after putting this to him last night he agreed. So I've ordered the new bits and am now just waiting for them to arrive.

This also means I now have an AMD64 3200+ and 1GB of PC3200 ram spare. ;) So finding a socket 939 board to stick them in would be nice.