[Gllug] VGA problem??

[Alistair Mann]

Chris Bell wrote:
> Hello,
>    I have been asked to look at a laptop which appears to fire up, but
> nothing appears on either the internal or external screens. A comment from
> someone else that there appears to have been a rash of VGA failures recently
> seems to have stirred a distant memory of a virus which reset the chip gain
> to minimum. Am I correct? Nothing found on Google yet.

The Chernobyl virus attacked some BIOSes, but not VGA in particular, and
required a Win9X environment.

I've seen many flat screens fail where there is "nothing on screen" but,
on closer inspection, one /can/ see an image, but at 2 or 3% the
brightness of normal. That happens when the power to the screen is lost,
but the signal itself -- which is carried on a very small charge -- is 
not. Plugging power back in to the motherboard or replacing burnt out
components helps, and sometimes so can flexing the display in the manner
of Rolf Harris' wobble board -- as a temporary measure.

Similarly I've seen the signal ribbon work loose from the motherboard,
during which time the screen is 'bright' black.

That doesn't explain the lack of external display, but then again I have
seen laptops which refuse to generate an external display until after
the POST.

I saw a post elsewhere here about failed GPUs. All the machines I've 
seen with a failed GPU generate diagnostic beeps at POST, so I suspect 
something else is happening...

Good luck with it,
-- 
Alistair Mann
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