Evening all,

Faye's Mam has a PC that I built last year, specs are as follows:
CPU: Intel Core 2 Quad Q8300 2.5GHz Socket 775 1333FSB 4MB L2 Cache
RAM: Corsair 4GB Kit (2x2GB) DDR2 667MHz/PC2-5300 Memory Non-ECC Unbuffered CL5 X2 (i.e. there is 8GB)
GFX: MSI 8400GS 512MB DDR2 DVI VGA Out PCI-E Graphics Card
Mobo: ASUS P5N-T Deluxe nForce 780i SLI Intel 775 DDR2 ATX MOTHERBOARD
HDD: Seagate 500GB 3.5" Barracuda SATA-III 6Gb/s Hard Drive - 7200RPM 16MB Cache
PSU: Sumvision 500W 20+4pin SATA 80mm Fan PSU
Optical drive: Something out of another computer, known to work
OS: Windows 7

I visited today and was told that a week or so ago "the screen stopped working". I thought it would be an easy fix (a cable must have come loose), however all cables seem fine. The power light comes on as does the HDD loading light, nothing appears on the screen whatsoever.
I don't have access to the machine now, but did reseat the RAM and GFX card. I noticed an odd whining, almost a fizzing from the PSU.

I'm looking at replacing the PSU as it didn't sound healthy, but is the above a typical system of a bust PSU? I don't want to order it, arrange to get down to Carmarthen and find that I need to buy something else...

Thanks very much,
Ben

I think it's unlikely to be that simple. If the PSU was shot, you wouldn't be getting any lights at all. Given you're getting power to the PSU (as you see the main power light come on) and the PSU is passing on some power (as you see HDD light come on as it spins up), it's not something like the PSU internal fuse having popped.

IMO, it's one of two things. Either the PSU is supplying power to the drive but not the main board (less likely) or the main board is shot (more likely). Swapping the PSU would at least confirm if the main board has gone kaput or not.

If you put the sound on, can you hear the machine booting into Windows?

If there's no display, my money's on either the motherboard or the graphics card.

If the machine boots into Windows, it's the graphics card. If if doesn't, it's probably the motherboard.

If the PSU's dodgy it could be shorting out the other components, particularly if the graphics card power requirement is towards the top end of the limits of the 12v rail on the PSU.

Does it beep when you turn it on?

One beep and everything on the motherboard is fine, more than one beep, that is the error code to say what is wrong.

1 beep would tend to indicate, that the video card is not working.

Thanks for your replies all,

The speakers aren't powered, just plugged in to the tower, I couldn't hear Windows start.
The green LED on the motherboard comes on and the CPU fan spins (not that that means the motherboard is getting the correct power).
I don't get any beeps whatsoever on boot.

My moneys on a duff PSU although it might be the ram.

Have you tried the machine with just 1 stick of ram and then using the other stick?

No, I didn't have time when I was there, and I won't be back for a few weeks, but I'll try it when I go down. Thanks very much

Sounds like the voltage regulators are shot on the motherboard (new mobo only cure) or the BIOS memory is weird-ed out.

Try unplugging PSU and clearing the BIOS by removing the battery, replace and fire up again.

If there are lights then the PSU is less likely to be the problem. Yes also try with just one RAM stick.