'Dead' PC

  SFP 20:13 02 Jul 2006

A few months ago my PC started developing a delay in switching on. When I pressed the power button the fans would start whirring etc but the POST beep wouldn't happen for a few minutes.

The time it took for the beep to occur slowly started to take longer.

About a month ago it stopped getting to the POST at all (but the fans, drives etc were all making the usual noises).

Some people told me memory was to blame, however I tried changing it to no avail.

I've tried changing the motherboard but now (with all the power cables plugged into it etc) it does absolutely nothing when I switch it on - it's like no power's getting to it at all and I'm pretty sure everything's plugged in to the motherboard properly.

Anyone got any ideas? It could be the PSU, but why would it suddenly stop working after changing the motherboard?

  LastChip 21:18 02 Jul 2006

It could well be a PSU problem. The only way you're going to find out is to change it, or take the machine to a technician that has proper test equipment.

The PSU provides a number of critical voltages and when the PSU starts, it does its own self test. If any of those voltages are outside their specified parameters, it will shut itself down.

  Fruit Bat /\0/\ 21:22 02 Jul 2006

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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

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.

2. Power supply calculator click here

Guide to changing PSU
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  SFP 21:28 05 Jul 2006

Thanks for the replies! I've tried the simplest thing and changed the fuse in the PSU to no avail. It seems strange that the PSU would fail straight after I install a new motherboard, expecially since I only bought the PSU 11 months ago.

I used the PSU calculator and it reckoned my 300W supply was good enough.

The PSU doesn't have its own power switch, the computer is switched on using the case's power button. I've plugged the power button lead on the case into the motherboard's 'pwr btn' connector. Could it be a problem here? Pressing the case's power button does nothing.

Another thing, I have no RAM installed as my previous motherboard took a different type. I don't expect the PC to work, of course, but a total lack of memory should stop the fans turning etc, should it?

  26trouble 08:44 08 Jul 2006

So what was your outcome? Was it the PSU or something else...I'm intrigued!

  DrScott 09:56 08 Jul 2006

Does your mobo have a LED? Most do, so you can tell when there is power getting to the board. The other sign of a working PSU is, with the case open, you should see the CPU fan move a little as soon as you turn on your PSU. If you don't have a switch, you can achieve this by turning the computer on at the wall and seeing if the CPU fan moves.

  SFP 18:52 08 Jul 2006

From one problem to another!

Inspired by DrScott I tried the 'CPU Fan twitch test' :) and it wasn't moving at all, so I've bought a new PSU and I've discovered the previous one must have died at the same time I changed my motherboard.

Having addded some RAM as well (fully pushed in so the clips are fully down) all that happens now is that I turn it on and the fans start spinning for a second or two and then it switches itself off.

Any ideas for the latest problem?

  DrScott 11:15 09 Jul 2006

Right, you need to check your CPU fan is properly seated - this new problem could be because the CPU is over heating and so the system is being shut down by the motherboard. Is the CPU fan spinning at all?!

Very happy to have been an inspiration - first time that's happened!!

  SFP 20:28 09 Jul 2006

Yes, the CPU fans works fine. I removed everything except the motherboard and the PSU. I got one long beep before it switched itself off. So, I added the RAM (but nothing else) and now get two quick beeps before it switches itself off. Having checked, this appears to mean 'POST/CMOS Error'.

What could that mean?

  LastChip 21:04 09 Jul 2006

If you're getting two short beeps, it's almost certainly a parity error.

The most common cause for this is RAM chips not seating properly. One cause is, you have not pushed the RAM into its slot hard enough. I know you said previously the clips had locked in, but please make sure you have this right. I can remember a thread that went into several pages and it ended up the RAM had not been pushed right home. It can be quite frightening how much pressure sometimes, you have to use to get it to seat properly.

Are you certain you are using the correct RAM? A parity error can also be caused by using parity memory in a motherboard that does not support it.

click here for a memory checker that will tell you exactly which memory your motherboard supports.

  SFP 17:59 10 Jul 2006

I'm certain it's the correct RAM, I referred to the motherboard manual before buying it. Having pushed as hard as I could to seat the RAM I now get a very odd beep code: two short beeps followed by four short beeps. Even the motherboard manufacturer's website doesn't list that as a valid code. The motherboard is a ASRock K7VT4A.

I'm starting to think I may just have to end up buying a new motherboard (my second in two weeks) - it's getting expensive, this troubleshooting!

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