2 failed psus

[Lewis2223]

Hi

Quick question. I recently built a new machine and had the power supply fail a couple of days ago. Machine spec as follows:

Gigabyte mobo
965 Phenom II
4Gb DDR3
XFX HD4890 1GB
1 DVD drive
1 SATA 320Gb Hard Disk

I used the 450W psu that came with the case and it was all working fine for a few weeks until a few days ago when it simply would not power up. Even the fans would not spin in the psu so it was clear the power supply had failed. As a quick test before I bought a new decent psu, I borrowed a 400W Antec PSU from a spare machine so that I knew for certain what to order. When I fired it up all the fans in the machine came on but the screen stayed black. There were no beeps and the machine did not post. So the next thing I did was to remove the graphics card and replace it with another spare pcie card that I had lying around. With this card, the machine then did post and a quick inspection in the bios showed the processor, all the memory, the hard disk and dvd drive ect all showed up as expected so it all seemed fine here. One thing I did notice though is that when the OS tried to load the initial black Windows xp screen it simply reset and restarted the machine although I suspect this was a driver issue since the spare gpu I tried was an nvidia card not an ati. I then put the hd4890 back in and again I got no post but I thought I would give it a minute or two to see whether it was just slow. Then the antec power supply blew too. Now at this point I have a number of possible causes and my question is how do I determine what went wrong and what I need to replace as I dont want to shell out for another psu and blow that too if there is a more fundamental issue. As I see it there are probably 2 possibilities:

- My PSUs were not up to the job and the high draw chewed them up and spat them out. Is this possible as I thought not enough power from the psu would just prevent it from starting up and not blow out the psus?
- There is an underlying fault with one of the components which caused the psus to fail. I expect the mobo and the gpu are the likely candidates however I am not sure how to really test them to confirm which, if any I need to replace.

Should I go ahead and try another higher spec PSU or is there other things I should check first before throwing more money down the drain? Any advice would be welcome. I just put my system into a psu calculator and it suggested I only needed 320W as a minimum so surely both PSUs should have been capable of running my rig temporarily right?

Thanks

 

[Rifter]

Dont try and run a 4890 with a 400W.

My AC 550RF didnt handle it, even though eveyone says my 550w should have been fine it wasnt. I would suggest a good quality 500w or higher PSU, think corsair, seasonic, Antec, PC P&C. Dont but the AC 550RF.

 

[Lewis2223]

Thanks for the advice, its much appreciated

So do you think it is likely that the GPU trying to draw more power than the psu could deliver could result in blowing 2 power supplies? As mentioned previously I thought if it was under powered it would just not work so I have never seen a psu pop like that previously despite having built a number of machines before. I just want to be sure I am not missing anything obvious before I risk a new PSU on it

 

[Rifter]

Its possible/likely the GPU was drawing too much power and thats what overloaded and eventually blew the PSU. Most PSU's that come with cases are very low quality and even if they say they are 450w or 550w cant supply the power of say a 400w corsair PSU on the 12v rail which is really the only one that matters. When i was having instability with my system it was only in games and bechmarks, it booted and ran fine otherwise but thats because the GPU was drawing alot less power at idle and in 2D so the system ran fine doing anything but gaming/furmark etc.

Its also possible that the case is grounding out to the mobo somewhere and thats causing a short and thats whats killing the PSU's, i have seen that in the past you might want to check thats the mobo is not shorting anywhere.