PSU Problem?

  Fatbloke1 12:54 06 Dec 2008

Last week we had a power cut whilst both my laptop and desktop were being used. The laptop immediately went to battery power so was ok. When the power was restored I didn't immediately check the desktop, when I tried to boot the desktop it would not start.

I have opened the case and when I switch it on the light on the motherboard comes on and the cpu fan starts, I can also open the two disc drives. However the hard drives do not start up and the fan on the graphics card does not start either. The hard drives and graphics card fan are fed from a different cable to the one that feeds the disc drives. I have disconnected and reconnected both sets of cables but this does not make any difference. I have also changed the position in which the leads are connected to the power supply, it has five different positions, but again this has not made a difference.

Am I looking at a complete new power supply or could it be that I only need to change the cable leading from the power supply to the hard drives and the graphics card? Or could it be something more problematical?


  skidzy 14:19 06 Dec 2008

This is from experience;

Due to a power cut there is an almost a certain chance the psu has bee damaged and normally non-repairable,as this has possibly gone it may have damaged your motherboard also.

As said,i have experienced this myself,and both needed replacing.
You could start with a new psu first,easy enough to change over,just check the physical dimensions.
Basically if a full ATX an ATX psu and so on.

  Fruit Bat /\0/\ 15:29 06 Dec 2008

TRy resetting BIOS to default first.

If still no good then its looking like PSU failure.

If renewing a PSU check:

1. The physical size of your PSU, some are hard to replace due to being a non standard size.
2. The amount of power need from the PSU don't skimp.
3 The correct connections for your equipment

1. Physical Dimensions

Besides the specs and form factors, the physical dimensions are also important factors in selecting a compatible power supply. Here is an outline of the physical dimensions of most standard power supplies:

# ATX: 6x3.5x5.5", HxWxD. Most common. Uses 4 mounting screws.
# Mini-ATX: 5x3.5x5", HxWxD. Rare size. Uses 4 mounting screws. Can be used in a regular ATX case, but often not the other way around.
# MicroATX: 5x3x4", HxWxD. Use 3 mounting screws. Not interchangeable with ATX or miniATX.
# Flex ATX: Even smaller than Micro ATX. Various sizes according to case specs; often not interchangeable.

Use the data above to determine if a particular power supply would fit your case.

The quality of a power supply can be estimated by its weight. While this is not a true scientific or thorough measurement of the power supply reliability, it is nevertheless a very simple and easy way for ordinary PC users to estimate and compare the quality of a power supply. Why weight matters click here

2. Power supply calculator click here

3. Correct connections
Some boards have 20 pin connectors others 24 pin
There is often a 4 pin plug required to power Intel CPUs
Molex D plugs for IDE HDD and CD/DVD drives
SATA power connections for latest HDDs and DVD drives.

Guide to changing PSU
click here
click here

  Fatbloke1 17:32 06 Dec 2008

Thanks, I've replaced the PSU before so will do so again and see whether that sorts out the problem.


This thread is now locked and can not be replied to.

Elsewhere on IDG sites

Best phone camera 2017

Stunning new film posters by Hattie Stewart, Joe Cruz & more

iPad Pro 10.5in (2017) review

28 astuces pour profiter au mieux de votre iPhone