Computer problem

psp83 · Oct 20, 2008, 12:12:52

Well the PC downstairs stopped working yesterday. I thought it was the PSU but the mobo has the green light on.

What could stop the PC powering up? pressing the button on the front doesn't do anything.

Motherboard dead?

Rik · Oct 20, 2008, 12:14:29

No beeps, Paul? If so, check for anything shorting the mobo to the case.

psp83 · Oct 20, 2008, 12:16:36

Quote from: Rik on Oct 20, 2008, 12:14:29
No beeps, Paul? If so, check for anything shorting the mobo to the case.

Nothing at all. everything seems dead except for that one green light on the mobo.

I took it all apart and put it back together. still the same.

Rik · Oct 20, 2008, 12:17:26

Is the PSU delivering power on all the rails?

psp83 · Oct 20, 2008, 12:19:27

dunno. not got a voltage checker, my one is broke.

Rik · Oct 20, 2008, 12:20:53

All you can do, then, is try a spare PSU if you have access to one. If it still won't work, it's probably the mobo.

psp83 · Oct 20, 2008, 12:24:32

well i was thinking about getting a package from novatech or something and turning the pc into a server as its quite old and i dont think i can get a mobo that will support the celeron cpu.

kinmel · Oct 20, 2008, 12:35:37

You can check if the power supply will jump start whilst disconnected from the motherboard by following this guide.

If the p/s fan doesn't spin up then the supply is duff, if it does start then follow this flowchart

Sebby · Oct 20, 2008, 19:02:28

Have you tried removing the power plug from the PSU and putting it back? Sometimes it "resets" things.

psp83 · Oct 20, 2008, 21:00:40

First thing i did, plus checked to see if power was going through the mains cable and it is.

LesD · Oct 20, 2008, 21:17:28

Quote from: kinmel on Oct 20, 2008, 12:35:37
You can check if the power supply will jump start whilst disconnected from the motherboard by following this guide.

If the p/s fan doesn't spin up then the supply is duff, if it does start then follow this flowchart

The guide is worth a

Alan so have one on me.

I have had a modicum of success on at least one occasion by giving the PSU fan a spin while pressing the PC's on button. Sometimes the back emf this creates can make a difference but if it does work the PSU is definitely on the way out.

psp83 · Oct 21, 2008, 15:28:16

is this voltage tester good enuff for computers?
http://cgi.ebay.co.uk/PRO-DIGITAL-MULTI-METER-VOLTAGE-VOLT-TESTER-TESTERS_W0QQitemZ110301761505QQcmdZViewItem?hash=item110301761505&_trkparms=72%3A1301|39%3A1|66%3A2|65%3A12|240%3A1318&_trksid=p3286.c0.m14

Rik · Oct 21, 2008, 15:36:19

Probably, Paul, but there's not a lot of information there.

psp83 · Oct 21, 2008, 15:37:52

what should i look for in a voltage tester for a pc?

Rik · Oct 21, 2008, 15:44:00

I'd want to know the accuracy for starters.

psp83 · Oct 21, 2008, 15:46:55

Doesn't say that on any i've seen, including amazon.

What should the voltage be anyways? i've forgot, been along time since something like this has happened.

Rik · Oct 21, 2008, 15:59:30

You really want good performance at low voltages. My Fluke gives a 40V scale with a resolution of 0.01V and an accuracy of +/- 0.9%, and a 4V scale with a resolution of 0.001V, same accuracy.

kinmel · Oct 21, 2008, 16:14:38

Quote from: psp83 on Oct 21, 2008, 15:37:52
what should i look for in a voltage tester for a pc?

I use one of these

Rik · Oct 21, 2008, 16:17:35

How do you find them, Alan? Are they sufficiently accurate to diagnose a fault, or simply adequate to test if something is working at all?

kinmel · Oct 21, 2008, 16:54:46

Quote from: Rik on Oct 21, 2008, 16:17:35
How do you find them, Alan? Are they sufficiently accurate to diagnose a fault, or simply adequate to test if something is working at all?

Works fine, just plug the P/S in and watch for the green lights.

They just pass or fail each rail.

You need much more serious kit if you want to start repairing/replacing board components though.

Is it worth all the effort though? Power supplies are cheap enough to just throw away these days

Rik · Oct 21, 2008, 16:57:17

So are a lot of computers, Alan.

kinmel · Oct 21, 2008, 17:12:19

Quote from: Rik on Oct 21, 2008, 16:57:17
So are a lot of computers, Alan.

Well as long as it's not an Apple replacement parts are cheap enough, but then you miss an opportunity to upgrade of course

Rik · Oct 21, 2008, 17:38:06

Real men don't eat quiche, eh?

psp83 · Oct 23, 2008, 18:58:59

I guess the mobo has died.

I've tried the jump start psu thingy and the fan started up.

The PSU tester also showed the +12v green light.

Sebby · Oct 23, 2008, 19:06:54

It does sound like it, Paul. Still, they seem to be fairly cheap these days.

Steve · Oct 23, 2008, 19:37:59

If PSU is ok , is the case power switch working?

Colin Burns · Oct 23, 2008, 20:05:56

probably the eaiest way to find out if it is would be to trace the switches cable back to the board and bridge the gap with a wire/paper click. to make it think the switch is there.

Steve · Oct 23, 2008, 20:11:04

Absolutely, I have used a screw driver in the past to bridge the gap

Glenn · Oct 23, 2008, 20:44:44

The fan runs off the 12v rail, most, if not all the motherboard run off the 5v rail, which then gets converted to 3.3v or less for the components.