Broken PSU / rig problems :-(

  AllanWalton 13:48 19 Aug 2010


I'm having an awful problem with my rig and it's beyond my technical ability to get to the bottom of it so i'm running out of ideas and was hoping you could offer some suggestions and advice.

I put together a new PC at the start of the year with the following components:

Radeon HD5850
Fractal Design R2 PSU (650w)
Gigabyte GA-790FXTA-UD5 (Socket AM3) Motherboard
AMD Phenom II X4 Quad Core 955
samsung 2TB Hard drive
Ballistix 240-pin DIMM, DDR3 PC3-12800 memory
Sony DVD drive
Windows 7 64 bit

It was fine for the first three months or so (apart from a windows 7 problem with restarting a pc from sleep mode and large hard drives causing a BSOD but a hotfix appeares to have fixed that) but then it started turning itself off (the power was turning off rather than BSODing or shutting down).

This gradually got worse and more frequent and then it stopped working completely.

I got the PSU replaced and it started working again but the same thing happened with it except it stopped working completely after just 5 days (so it didn't gradually get worse this time it just went).

The gfx card requires a 500w PSU (although the psu isn't listed in the certified list on AMD's website) so a 650w supply should be adequate (so I don't think it's trying to suck too much power through and blowing?). Looking at the total amperage on the 12V rail, the requirement is 40A and the PSU provides 50A so i'm not sure if that's likely to be a problem (?).

I don't think it's an overheating issue as the PSU is cold to the touch when running and I've got both sides of my case off to prevent air flow issues.

My only other guess is that there is a problem with the rig and the motherboard installation causing a short somewhere - Once I've got a replacement psu I'll be taking out all the components and trying to run the rig on top of the mother board box.

Does anyone else have any suggestions about how I can track down the problem and fix this asap? Is it possible it's a broken component somewhere? Should I be looking into getting other items replaced?

I've not got a lot of money and don't have another rig to test components in although I've been offered a cheap gfx card to try and test that against my ati one.

If anyone has got any other suggestions please let me know thanks.



  johndrew 14:50 19 Aug 2010

I may be wrong but I believe AMD certify components to ensure supplies and draws are known and stable as some components are susceptible to fluctuations in power.

If your PSU is exceeding the ripple values - and PSUs in common with other units vary with both use/time and temperature - could this be causing your difficulty?

A short sounds unlikely as it will be present at all times - unless it does permanent damage in shorting.

Have you tried booting into BIOS and leaving it standing to see if it shuts down without the OS functioning?

  citadel 17:04 19 Aug 2010

650 psu if fine, normally if its cool to touch means its got good components. ive got a 5870 and a 625 enermax and its ok.

  Bris 20:20 20 Aug 2010

Hi Allan

I had a similar problem where the PC worked OK for about a month and then started powering down completely and then powering up again with beeps that were not in the manual and Gigabyte were no help. It would go through this cycle ad infinitum.
Turned out it was a faulty RAM stick.
PSUs are pretty robust especially if of a well known make and contain circuitry that monitors current flow and will protect the PSU in the event of too much as in a component drawing too much current. Could be due to a short but more likely to be a faulty component.

I think you are on the right track when you suggest stripping the components out and trying with as little plugged into the motherboard as possible.

Try removing the HDD cables, all RAM except 1 stick, the optical drive, any USB devices etc and then try running it up.

If you can, try the PSU in another machine as it may be that its OK but is current limiting to the point of refusing to power up.

Good luck.

  AllanWalton 13:30 23 Aug 2010

Thanks for the replies guys - it's appreciated.

I've sent the PSU back to the vendour now so I'm waiting for the next week or so until the new one arrives (hopefully). Then I'll run it with the mobo outside the case, 1 stick of ram (i've only got two - it's going to be a rigth nightmare if it is a dodgy ram stick and I take the wrong one out lol ) and a minimal set up and see what happens - I've got a spare gfx card that I can use to test that too so fingers crossed. I'll reply on here when I've got a bit more info.

thanks again.


  Bris 09:43 24 Aug 2010

Hi Allan

Just a further thought. It may be a faulty case power switch, if its stuck in it is likely to prevent it powering up. You can check this out by tracing the wires back from the switch to the motherboard header or check the manual, and remove the plug exposing the two pins. With power applied to the PSU, briefly short out the two pins with a screwdriver blade which should cause the PSU to power up.

Know what you mean about the RAM sticks, I had 4 and one was faulty, guess which one I chose to test the rig out, thats right the faulty one - should have known better.

Looking at your setup, even though you have a high powered graphics card a 650 watt PSU should be more than adequate.

Lets know how you get on.

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