PC Switched Off and wont Switch back on.

  Commander Straker 15:56 12 Aug 2009

Some time ago I replaced the PSU in my aging Mesh machine. I wonder if this has now died. The PC was working but then switched itself off. I switched it back on again but after a few minutes it switched off again. Now it wont turn on. There is a green light showing power on the motherboard and TV card but no fans start up and there is no boot up activity. What do you think ? Thanks

  Chris the Ancient 16:38 12 Aug 2009

To me, it does sound a bit like a bust psu. Albeit, two led indications seem to show that there is some power there, but not the right amount and in the right places. Most fans are directly driven from the psu, so that does sound as though that even if it's not totally dead, it's pretty close to it.

  Fruit Bat /\0/\ 16:44 12 Aug 2009

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

  shellship 16:47 12 Aug 2009

Before you try anything drastic, turn off at back by mains connection, unplug at back so totally isolated and wait for half an hour to let any static dissipate, reconnect and try again.

  Commander Straker 19:36 12 Aug 2009

Thanks for quick response. I did try the 'static thing' as you suggested shellship but no joy. I'm going to try a PSU replacement - its our secondary PC so I wont go over the top as the PC is pretty old now.

  Commander Straker 20:11 17 Aug 2009

Just to report that I changed the PSU today and after running a few hours all seems to be functioning correctly. Thanks for your help all.

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