Mystery of the dead PC

  RichardChemist 09:48 24 Apr 2009

I have a Mesh Express TV PC:
Intel E6550 processor
XP media
Nvidia nforce networking controller
Belkin wireless G desktop card
500Gb HDD ST3500630AS
GForce8600GT graphics
Sound SAA713X

Yesterday, all was working fine in the morning. I manually put it to hibernate (auto hibernation stopped working some time ago)

When I went to wake it up later, the blue light on the main button was not flashing. I pressed it anyway, but nothing happened.

After some fiddling it started. But the wired network connection said the lead was unplugged. It was plugged in, and swapping for a known working cable/connection, still gave the same message.

I tried the wireless, which promptly said it was connected, but would not go through to the internet. ipconfig /all reported a wireless connection but nothing further. It would also not talk to the other computers on the network or even give me access to the router screen.

I turned it on and off a few times without problems, but did not achieve any internet connection.

This morning, I switched the PC on again, but nothing had changed. I turned it off again, and the screen announced Windows updates 5-7 being installed. I hoped that this might have fixed things and tried to switch it on again, but the PC remains resolutely dead, with no fans starting or disk activity

There is a green LED illuminated on the MoBo, so some power must be getting through.

Does anyone have any ideas, please?


  OTT_Buzzard 09:54 24 Apr 2009

PC remains resolutely dead, with no fans starting or disk activity

THere's not much that can cause this. Checking the power supply is step one, if all is well there then change the wall-socket you are using.

Other than that, sometimes fried CPU's can cause the symptoms you are seeing.

  rawprawn 09:56 24 Apr 2009

Can you get into Safe Mode and try a system restore?

  keef66 10:29 24 Apr 2009

tricky to get into safe mode if the pc won't start.

Something that has worked for me in the past is simply unplugging from the mains for a couple of minutes then reconnecting and trying again. No idea what this does but it has started our moribund desktop on a couple of occasions. Another long-shot but quick and cheap possibility is removing the cmos battery for a few mins.
Failing that, as OTT suggested, try installing a known working power supply.

If that makes no difference it looks like a mobo fault, and unless you can borrow one to swap in and out your components, it's an expensive business to diagnose

  rawprawn 11:48 24 Apr 2009

This is so true, I must try harder! ;))

  RichardChemist 13:21 24 Apr 2009

Thanks to all of you for your good advice.

I tried unplugging, but with no luck.

Using a meter, I checked that the power supply switch was working. I then removed the connector from the MoBo and shorted the green pin to earth. The power supply fan started up, and I measured all the right voltages in all the right places.

I have just taken out the battery, with no effect.

I guess that the time has come to bite the bullet and order a new MoBo.

Thanks again


  RichardChemist 12:43 02 May 2009

I bought the new motherboard, which has just arrived. I fitted it, but the PC is still dead. Does that mean it's the processor? I don't want to order another expensive item only to find that it's still not working. Is there anything else that I should look at first?



  OTT_Buzzard 13:17 02 May 2009

Before you go for a new processor, spend some more time working on your PSU - its far more likely to be the cause of your issues.

Note that you need to have your PSU plugged in to your mobo and the system powered up (as far as you can!) in order to test properly. Not sure if that is what you have already done, I don;t mean to 'teach you to suck eggs'.

The link below gives a fairly good guide on how to test.

click here

  RichardChemist 13:47 02 May 2009

Thanks for the thought.

My problem is that the power supply won't even spin up the fan because it doe snot seem to be getting any signal from the motherboard.

However, after disconnecting from the motherboard, I did short the green wire on the ATX plug to earth, which simulates the switch-on signal from the MoBo.

The fan then started to spin, and I was able to measure 3V, 5V and 12V on the appropriate wires. Of course, this does not guarantee that the PSU is not failing when I try to take a real load from it, but as there is absolutely no response at all when I pres the front panel button, Ifeel reasonably confident in not blaming the PSU.

Btw, I did check that the switch itself is working.


  OTT_Buzzard 13:58 02 May 2009

The fan then started to spin, and I was able to measure 3V, 5V and 12V on the appropriate wires

Was this done with the ATX connector plugged in to the mobo?

  OTT_Buzzard 14:01 02 May 2009

Sorry, that was a short sharp post!
A little more info:

Power supplies don't always give the same voltages when they are not under load. For an accurate reading the connectors have to be plugged in to the mobo. Its worth not only checking the ATX connector, but also the power supply to the CPU (it will be a 4, 6 or 8 pin connector, separate from the main ATX connector)

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