Help please it's driving me mad

timbo · #1 20th Nov 2007, 10:23

Ok here we go. Although there is power etc my computer won't start when I press the on button by itself and I have to unplug the DVD power supply at rear of DVD and plug it back in before it starts to boot. I have swapped power leads and tried various combinations but it's always the same. Checked the CMOS start sequence it's ok. Disconnected DVD completely, it still won't start, disconnected 2nd DVD drive too, it still won't start. It always needs the same DVD power plug to be in at the beginning and then disconnected and reconnected after pushing on button in order to start boot sequence.

I know I probably shouldn't do it because of spikes etc but it can't be rocket science for you experts out there to give me a clue - I'm only a simple semi-retired engineer who is fairly logical in his approach but unfortunately not one who deals with computer hardware.

In anticipation.

**philthomas** · #2 20th Nov 2007, 10:43

LOL .... how on earth did you work out that that sequence would help ??

It sounds to me like you have a faulty PSU ... how old is the PC ?

**serverguy** · #3 20th Nov 2007, 12:23

I agree it sounds like the PSU.

How old is it?

timbo · #4 20th Nov 2007, 16:25

Quote:

Originally Posted by philthomas

LOL .... how on earth did you work out that that sequence would help ??

It sounds to me like you have a faulty PSU ... how old is the PC ?

Thanks for your response the answer to your question is sheer luck really, I was looking for a bad connection to try and solve the problem and pulling and replacing plugs and sockets with the power on and hey presto a quick beep and up she boots (no lectures please). Anyway the computer is about 13 months old (aren't they all when things go wrong!!)

Any logic to why you think it's the PSU - there are 2 separate 4 pin outputs that provide power to bits and bobs each of which has several 4 pin parallel connectors and I have tried them all but each time it's the same. There is also a multi-pin connector that goes into the MB. The question is why sould it work when I've unplugged it with the power on and then plugged it in again, there is power to the MB as soon as I switch on in the first place as the fans work and a few LED's come on so how can it be the PSU? Don't mean to be a bore it's just the engineer in me trying to find a logical reason- or half of one at least.

**philthomas** · #5 20th Nov 2007, 17:06

From the symptoms you describe and the non starting, without you unplugging/replugging in the Molex connector, the most likely cause is the PSU. My guess would be that the PSU is dying and is behaving erraticly and somehow your actions seem to wake it up/kick start it into action.

There could of course be other reasons, like a faulty motherboard or CPU, but the PSU is relatively cheap and easy to replace and like most things, when it's a process of elimination, you need to try the cheapest things first. i.e. you wouldn't change the alternator before you checked the plugs

There are ways of testing the voltage outputs of PSU's, but you would need to test it under load and in the machine, using a Digital Multimeter. This website gives plenty of details, if you feel so inclined, but if it were me, I would just swap it out. If nothing else, it will eliminate it from the list :

http://www.informit.com/articles/art...1105&seqNum=12

timbo · #6 21st Nov 2007, 05:48

Thanks Phil - any advice on where to purchase a good one and minimum wattage I should go for.

**philthomas** · #7 21st Nov 2007, 06:27

Without knowing the system specs, it's a bit hard to say, but when you remove the old one, it should show the wattage on the case. I would add 100w to whatever is in there now and you should be fine.
Dont go for the cheapest, plumb for a medium priced unit.

Some manufacturers, however, fit non standard PSUs with non standard motherboard plugs, so you are hooked to them for any replacements, so before parting with your cash, make sure yours is a standard unit. If in doubt, it might be a good idea to find a local supplier, to compare and who will exchange it, if it's not right.

**serverguy** · #8 21st Nov 2007, 11:03

I would look for something of about 450W. This might be a bit overkill but they are so cheap now you may as well work a more powerful one less than max a lesser one out. Just my opinion.

timbo · #9 22nd Nov 2007, 11:58

Thanks guys current PSU is 400 Watts. Thinking of buying Trust 570W Pro Psu Dual Fan through Amazon for £26 + P&P. Your thoughts please.

**serverguy** · #10 22nd Nov 2007, 12:15

That PSU would be fine.

It is not the best on the market but seems OK value.

Don't expect a silent high quality PSU but I am sure it will be better than your old one.