Display problem - where does the fault lie?

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A couple of weeks ago, my computer (with a 5-year old 250w unbranded PSU -
the rest of it is about 2 years old) stopped turning on when I pressed the
power button.  A bit of turning off/on the power at the plug eventually
persuaded it to turn on.  It did this a few times and hasn't been a problem
since.  At the time I thought, "PSU's on its way out..."

Today, the machine's been idling for a while, and I come to find it
semi-frozen - the display looks like it does when you hold a cellphone
that's in use right next to a monitor - and the cursor moves jumpily across
the screen when the mouse is moved.  Doesn't seem to accept any keyboard
input, won't "do anything" in response to mouse clicks.  I power off, power
on - display is corrupted right from the first screen (BIOS information,
POST).  Boots into Windows, runs normally but with corrupted display, and
then goes into that semi-frozen state again.

I tried another monitor, same thing.  I left it to cool down for a while,
same thing.  I throttled back the CPU, unplugged the hard discs etc - same

I then removed the graphics card (an NVIDIA GeForce FX5700 Ultra) and dusted
off the cooling fan, the AGP slot, and the card itself.  I also dusted the
CPU fan a bit, but it wasn't really dusty.

Following this, the display was almost normal when I booted up, and Windows
looked fine until I ran a game.  The opening cutscene was slightly
corrupted, the menu display very corrupted, and the in-game display was
utterly whacked out.  The PC ran fine after returning to Windows, but the
display never cleared up again, until I rebooted.  Then same thing - fine
until I ran a game, corrupt afterwards.

I'm a bit stumped now.  I'm not sure where the problem lies.  I'm assuming
it's not a driver fault because the display was whacky even before loading
Windows, and I don't have much experience with hardware problems.

Please help!


Re: Display problem - where does the fault lie?

On Wed, 14 Dec 2005 18:04:41 GMT, "Charles Tosh"

Quoted text here. Click to load it

You've been using a poor generic PSU that's unsuitable for
the system... at this point you may have worn out capacitors
and damaged several parts and to nail this down you will
have to try all parts isolated- easiest done with a 2nd
compatible system for parts substitutions.

First thing I'd do is get a better power supply and just try
the system.  Continuing to use this questionable one and
diagnosing parts acting up (possibly due to) with poor power
could leave the initial problem.

Inspect capacitors on the motherboard, and in the power
supply after having left it unplugged from AC  for several
minutes.  Take voltage readings of the power supply output,
at the connector to the motherboard with a multimeter, NOT
on the open PSU unless you are competent to do so.

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