On 29 Mar 2008 19:33:09 GMT, chris <invalid@invalid.invalid>
wrote:

>My AMD64 desktop has been running happily for over a year. A couple of
>nights ago I was checking my e-mails when the screen froze. First
>reaction was it was a mouse failure, but nothing worked - keyboard did
>nothing, couldn't Alt-Tab through screens. Ctrl-Alt-Del didn't work. So
>power off. Power on: things start OK, but nothing on screen. Tried
>booting from DVD - no joy. Hoping it was only a graphics card (and not
>HD)

It is rare for a hard drive failure to keep a system from
POSTing at all, normally system will post and stop at
enumerating the drive, fail to find a viable boot device,
and/or you'd hear a clicking sound from the drive.

However if there were any doubt you can just unplug the
drive and the system should still display video if posting
and video card is working.




>...I was happy to buy a cheap card to test theory.
>Machine started up, I
>was able to log on, but then display froze again, and I couldn't get it
>goig again. So tried again the VGA connector on the M/B (even though M/B
>has no graphics built-in).

? ? How is there a vga connector on the board if the board
has no built in video? What motherboard make and model?

If possible you should try the old video card in another
system, I'm suspecting you might be having a progressive PSU
failure.



>Hadn't worked before, but this time I got a
>display; then as I watched the progress bar (this is running Linux) the
>display went off again, and the 'no video signal present' message
>appeared.
>
>I'm at a loss as to what to try next. I suppose the PSU could have gone
>faulty. Note that I had done absolutely nothing to the PC before this
>started. It's a MSI K9AGM, originally with Club3D Radeon X1600 VGA card,
>and NorthQ PSU - I wanted a quality PSU.

What exact model? NorthQ aren't good quality PSU, then the
situation is made worse when they lower the fan RPM which
increases temp, reduces life. This is a potential weak link
in your system - but we can't be sure yet it is the problem.
You might leave it unplugged for a few minutes, open and
inspect it (unless you have a valid warranty still and hope
to exchange it), and with it closed again measure the
voltage with a multimeter though this won't find all kinds
of faults.



>
>What's the best thing to try next? I can maybe get a colleague to test
>the VGA cards, but I don't have many options for swapping components.

Yes, have someone test your original video card. It could
be dead, and if failing it could have a lossy part that put
a strain on the PSU, or more likely the psu was failing and
put a strain on the video card... but odds are fair the
video card is ok provided it didn't have a fan failure and
no visible corruption on-screen like artifacts.

If you had a spare, good PSU that would be the next thing to
try - or if not, buy one from someplace with a good return
policy. If your old PSU just popped a capacitor it might be
repairable, but I mean by you or a friend, it isn't worth
having a shop do it... then it may need that quiet fan
swapped out for one moving more airflow.

I hate to lecture but PSU manufacturers don't like to make
noisey products, they do it to provide more cooling margin.
Better PSU still have to be derated to a lower output power
when used with low flow fans or aggressive fan control
circuits in the psu so it makes it all the more important to
pick one with a higher wattage rating than you otherwise
would or from a company that rates very conservatively. I
have not seen all NorthQ models but those I have seen online
are not rated conservatively, look like a typical $25 300W
PSU with a higher peak rating on the label.