Re: CPU or Motherboard

The message <441adf61$0$23290$db0fefd9@xxxxxxxxxxxxxx>
from Count de Monet <me@xxxxxxxxxxx> contains these words:

Got a PC in for repair.

Won't power up, nothing, no PSU fan, no CPU fan. My first thought - PSU.
Replaced with brand new on but nothing. Return to the old PSU tried the
green to black short trick and the old PSU fires up fine.

Next, removed the motherboard from case onto workbench (antistatic mat)
and connected the new PSU to motherboard with only the RAM installed,
nothing.

Swapped RAM for new module, same result, nothing.

This only leaves two possibilities, Motherboard or Athlon XP 2.6 CPU.
Which is the most likely to have failed? The CPU does not appear to have
overheated and the customer reports a few 'crashes' before total failure.

The motherboard is a MSI and the PC is a eMachines (yes I know)

If the PSU is by 'Bestec', connect it to the mains without any load
(safest thing to do) and measure the VSB line (purple wire). It's
_supposed_ to be 5 volt +/- half a volt maximum variation. I bet you'll
find it's higher than 6 volt!

I only wish I'd thought to do this simple test B4 replacing the
origional P4 MoBo with a new one. :-(

The replacement MoBo worked fine for the few hours it took to repair
install winXP and the subsequent windows updates and the usual anti
spyware installs et al follow up stuff.

When I set it up for a final checkout a couple or three weeks later,
when the customer finally deigned to call in and cough up for the
repair, I noticed a rather high standby power reading (over 12 watts,
creeping to 16) but, sadly, didn't take the hint to check the VSB until
after the board threw a wobbly and then started behaving just like the
origional board by not responding to the PS signal from the front panel
power button.

The reading I got, btw, was 6.33 volts. Not enough to immediately blow
the standby part of the chip, but enough to slowly "Cook it's Goose".
:-(

I had a spare 'Spare Mobo' so was able to replace that as well as the
PSU in time for my customer to witness the final phase of the repair
work.

I was able to reassure him that, having finally discovered the real
culprit for what had started off as mysterious stability issues which
had eventually culminated in a dead MoBo, he would be unlikely to suffer
any further (out of warranty) problems for at least another year.

The PSU's I use have lasted many years before the very few that have
failed did so in a graceful way (as opposed to Bestec's _DIS_graceful
way!).

With a company like eMachines, who have the ignorance (or gall)[1] to
put a label on the front 'boasting' 128MB (actually only 120MB or less,
after the inbuilt graphics has swiped 8 or more MB's worth) and winXP,
what can you expect?

[1] Probably gall. I suspect they wanted to avoid customers 'with a
clue' and hence not be troubled by people not easily fobbed off by their
tech support chimps.

HTH

--
Regards, John.

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