Shortlived PSUs...NOT

[JJ \(UK\)]

Hi

The other week I powered on my PC but within a second of doing so it made a
loud, kind of 'farty bang', noise and cut out. A test with a
known-to-be-working power cable just produced a similar noise when attaching
it to the power input on the PC.

So I used this as an excuse to buy a new case with a 400w PSU.

Nice.

That is until after about the 3rd or 4th power up at which point it also
lost power - albeit without the dramatic sound effect from before.

So the question is, is it possible that one of the components is causing a
short circuit or 'back surge' (I'm no electrician so this might be complete
nonsense) thus blowing out the PSU? Bear in mind that I'd have been using
completely new power cables as supplied with the PSU that came in the case
so a cabling fault seems unlikely. Or have I just been incredibly unlucky?!

Regards and thanks in advance

JJ (UK)

So anyway, I took the darn thing back to the shop where they proved that
it's not the PSU that's the problem (by attaching a known-to-be-working PSU
to the motherboard with the same result).

They suggested I disconnect all the PCI cards apart from the Video card
(although I don't see why not that one as well - at least long enough to
prove the point) but it's made no long term difference.

All that happens is that as I release the power button there is a brief show
of power then nothing.

Something's shorting out somewhere I guess...any ideas?

JJ (UK)

 

[SteveH]

So anyway, I took the darn thing back to the shop where they proved that
it's not the PSU that's the problem (by attaching a known-to-be-working
PSU
to the motherboard with the same result).

They suggested I disconnect all the PCI cards apart from the Video card
(although I don't see why not that one as well - at least long enough to
prove the point) but it's made no long term difference.

All that happens is that as I release the power button there is a brief
show
of power then nothing.

Something's shorting out somewhere I guess...any ideas?

JJ (UK)

I think its probably safe to say that when your PSU blew, it took the
motherboard (at least) with it.

SteveH

 

[JJ \(UK\)]

I think its probably safe to say that when your PSU blew, it took the
motherboard (at least) with it.

Perhaps, but the motherboard was working fine for a few reboots after I
rehoused it in the new case...

JJ (UK)

 

[SteveH]

Perhaps, but the motherboard was working fine for a few reboots after I
rehoused it in the new case...

JJ (UK)

See if the board will power up out of the case. If it does, then you likely
had a short somewhere under the board.

SteveH

 

[JJ \(UK\)]

See if the board will power up out of the case. If it does, then you likely
had a short somewhere under the board.

OK, it's a plan. Now if I can juuuuust get the kids out of the house for
long enough...

JJ (UK)

 

[w_tom]

The power supply 'system' is three components - power
supply, motherboard controller, and power switch. Which is
the problem? The shop should have been able to answer that in
but a minute using the 3.5 digit multimeter. Is motherboard
power supply controller bad? Meter could have answered in but
a minute.

Procedure confirms integrity of the power supply system.
Once all three 'system' components are verified, then move on
to other suspects.
"Computer doesnt start at all" in alt.comp.hardware on 10
Jan 2004 at
http://tinyurl.com/2t69q and
"I think my power supply is dead" in alt.comp.hardware on 5
Feb 2004 at
http://www.tinyurl.com/2musa
Voltages should measure in the upper 3/4rd limits in chart.

Without specific numbers, then we don't have any idea where
to begin fixing. The shop had a right idea. Once PSU
'system' is verified, then remove everything - including video
card. The computer should consist only of CPU, motherboard,
power supply, power switch, and speaker. No Ram. No
keyboard, etc. If only these parts work, then speaker should
beep an error code.

Don't spin wheels. This strip down test tells us nothing
and may not even be necessary until after meter has been
obtained and reports numbers. This is undeniably the fastest,
cheapest, and most effective procedure to - the fundamental
point - find the reason for failure. Don't worry about fixing
anything until failure is first identified - to solve problems
faster.

Final point - if power supply caused motherboard failure,
then the power supply is 100% defective when purchased. Power
supplies must fail and still not damage any other computer
component. They failed to learn of basic power supplies
functions. They buy power supplies only on price. Supplies
that are missing functions required even 30 years ago.
Functions that protect all other computer components from a
failing power supply. Any computer assembler that does not
know this - walk away quickly.

Also rather embarrassing that your computer shop did not use
a multimeter to report, up front, what was and was not
working. Swapping in a power supply required more labor, put
your motherboard at increased risk, and still told us little
about where to look for the failure.

 

[SteveH]

Don't spin wheels. This strip down test tells us nothing
and may not even be necessary until after meter has been
obtained and reports numbers. This is undeniably the fastest,
cheapest, and most effective procedure to - the fundamental
point - find the reason for failure. Don't worry about fixing
anything until failure is first identified - to solve problems
faster.

The 'strip down test' could prove plenty. It's possible that the o/p
accidentally put a mobo standoff in the wrong place and is causing a short
somewhere under the mobo, which should be immediately obvious on removal of
the mobo, and may not be revealed by use of your 3.5 digit meter.
It could be that the system is not starting because the CPU fan tacho isn't
working (or the plug is in the wrong header on the mobo), thereby
trigggering the system overheat protection which many mobos have (I didn't
see you reccommend checking this).
BTW, still top posting I see.

SteveH