dead system

[Fireburst]

I am having problems with a friends system. When the power button is pressed nothing happens (no fans start).

On opening the case the Asus P5K-E wifi-ap board shows the green power light. I shorted out the psu (green and black) and tested the voltages and they all tested ok. I noticed however that the psu fan didn't spin when shorted out which I thought it should?

I have tried disconnecting everything from the power and just having the power plugged into the motherboard with just the cpu + heatsink connected and still nothing. I reset the cmos and still nada.

I then tried shorting out the power button to discount that but still nothing. I guess that means it's either the cpu or the motherboard unless someone else has any suggestions? If it's down to the cpu or motherboard (or indeed both) is there anyway to discount one or the other?

 

[Tealc]

When you say no fans start, are all fans powered off the motherboard or are some powered direct by PSU using Molex connectors or a fan controller perhaps?

Most PSUs fan will spin when turned on, the only exceptions will be semi-passive models (ie very expensive ones).

Did you have some load on the PSU when you were testing, such as fan connected by molex? You could be measurinf residual voltage from capcaitors.

 

[Fireburst]

The fans which were connected directly spun when the psu was shorted (however these were not connected when I tested so I will retest under load). Not sure if its semi-passive (its a colorsit 400w not sure which model).

 

[Tealc]

It's a colorsit 400w.

Oh dear. A quick google search shows me a Colors IT 400W PSU looks remarkeably like a Q-Tec PSU. Maybe whoever is the OEM manufacturer produces the same units and they get rebranded by some other companies.

The 400W unit is available, or used to be available, for the princely sum of £15 which puts this PSU down as a dirt cheap 400W unit.

I'm going to stick my neck out and suggest that this cheap 20A/12v railed PSU has failed to raise enough power to provide sufficient voltage for the PC to properly start.

I would also suggest that your friend were to invest in a good PSU with solid power output. Which one though?

The highly recommended Corsair 400W perhaps http://www.overclockers.co.uk/showproduct.php?prodid=CA-017-CS&groupid=701&catid=123&subcat=

If the machine is low spec and not used for gaming, overclocking or anything remotely interesting then maybe one of OCUK's low end supplies http://www.overclockers.co.uk/showproduct.php?prodid=CA-025-OP&groupid=701&catid=123&subcat=1709 or maybe one with a higher wattage, for future growth http://www.overclockers.co.uk/showproduct.php?prodid=CA-027-OP&groupid=701&catid=123&subcat=1709

 

[Fireburst]

Thanks for all your help... its was a faulty psu Just ordered a new one.

 

[whipitrnd]

its probley your psu. but if your psu blown it can sometimes take out your motherboard, but i had this problem wasnt powering up, but i fount that my cathode switch light metal wire bit was touching the case which was cutting it out so not letting me power it on.