Shortlived PSUs

[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)

 

[Dave C.]

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)

Inexpensive power supplies are alarmingly unreliable. It's possible you've
just been unlucky. You should check your motherboard though to make sure it
is not grounding to the case anywhere. Like, maybe a standoff in the wrong
location, or a loose screw or something like that. -Dave

 

[JJ \(UK\)]

Inexpensive power supplies are alarmingly unreliable. It's possible you've
just been unlucky. You should check your motherboard though to make sure it
is not grounding to the case anywhere. Like, maybe a standoff in the wrong
location, or a loose screw or something like that. -Dave

Thanks, but, what's a standoff?

JJ (UK)

 

[Dave C.]

Thanks, but, what's a standoff?

JJ (UK)

It's the little post that sits between the case and the motherboard. There
needs to be several of them (usually about a half dozen) to hold the
motherboard in place. Usually, screws are used to fasten the motherboard to
the standoffs. However, you have to make sure that there are no standoffs
in areas where the motherboard does NOT fasten to them. In that case, they
can short out the motherboard. -Dave

 

[JJ \(UK\)]

It's the little post that sits between the case and the motherboard. There
needs to be several of them (usually about a half dozen) to hold the
motherboard in place. Usually, screws are used to fasten the motherboard to
the standoffs. However, you have to make sure that there are no standoffs
in areas where the motherboard does NOT fasten to them. In that case, they
can short out the motherboard. -Dave

I see. Thanks. Kind of puts a lie to the ATX 'standard' a bit though. At
least when shops claim that it's a straight swap!

I take it that this won't apply if there is a hole for the stand off but no
screw used. i.e. the motherboard isn't actually screwed in to a stand-off in
a certain location....

JJ (UK)

 

[spodosaurus]

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)

Count yourself lucky if the first failure didn't kill or seriously
damage components (which will fail soon enough). Don't buy cheap PSUs.
You didn't say what brand of PSU the second (400W) one was. I like Antec
PSUs, and that (or similar high quality and quiet) will go in any new
computer I build.

Cheers,

Ari

--
spammage trappage: replace fishies_ with yahoo

I'm going to die rather sooner than I'd like. I tried to protect my
neighbours from crime, and became the victim of it. To jump to the end
of the story, as a result of this I need a bone marrow transplant. Many
people around the world are waiting for a marrow transplant, too. Please
volunteer to be a marrow donor:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[spodosaurus]

I see. Thanks. Kind of puts a lie to the ATX 'standard' a bit though. At
least when shops claim that it's a straight swap!

I take it that this won't apply if there is a hole for the stand off but no
screw used. i.e. the motherboard isn't actually screwed in to a stand-off in
a certain location....

JJ (UK)

No. There are sometimes holes in the motherboard that are not meant for
standoffs. If the metal standoff touches the motherboard in a place
where it's not meant to, it can short to the case. Most standoffs can be
unscrewed from the case (sometimes requiring the use of pliers for
starting the twisting) and moved to different positions on the
motherboard plate.

Cheers,

Ari

--
spammage trappage: replace fishies_ with yahoo

I'm going to die rather sooner than I'd like. I tried to protect my
neighbours from crime, and became the victim of it. To jump to the end
of the story, as a result of this I need a bone marrow transplant. Many
people around the world are waiting for a marrow transplant, too. Please
volunteer to be a marrow donor:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[Dave C.]

I see. Thanks. Kind of puts a lie to the ATX 'standard' a bit though. At

least when shops claim that it's a straight swap!

I take it that this won't apply if there is a hole for the stand off but
no
screw used. i.e. the motherboard isn't actually screwed in to a stand-off
in
a certain location....

JJ (UK)

Well you don't necessarily need to use every mounting hole. I've seen some
ATX mainboards with nine mounting holes. That's definitely overkill. I've
also found it is not unusual to find a brand new ATX case with standoffs
pre-installed in areas that do NOT match some of your ATX mainboard mounting
holes. Thus, it would be easy to install a mainboard with an extra
standoff. -Dave

 

[Guest]

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.

I don't know if an electrolytic capacitor popped, but a screeching
coil can sound like a rip, although a coil wouldn't bang unless its
core cracked (and I doubt it would crack a second time).

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?!

What brands are those supplies, and, in case the brands are unknown,
what safety certifications and certification registration numbers do
they have? Any decent 400W supply should be able to run any
single-CPU system without too many disk drives in it, but the 3-4
turn-on attempts indicate your 400W supply may not be a 400W supply.


Good power supplies don't fail when overloaded, except from high
voltage surges on the AC side. A back surge can be caused only by
inductance, but the output filter capacitors should block any such
surge a motherboard can generate before the rest of the power supply
is hit.

 

[JJ \(UK\)]

"JJ \(UK\)" <[email protected]> wrote in message

What brands are those supplies, and, in case the brands are unknown,
what safety certifications and certification registration numbers do
they have?

The case is a Meridian ME09A. The PSU was supplied with it and already in
place. No idea about the certifications/registrations though.

JJ (UK)

 

[Zotin Khuma]

The case is a Meridian ME09A. The PSU was supplied with it and already in
place. No idea about the certifications/registrations though.

JJ (UK)

If I may jump in kind of late. Was the 'farty bang' you described an
explosive sound accompanied by a 'phfffft' sound ? That sounds very
much like a capacitor venting, probably the main filter capacitors. If
that's the case and it happened a second time (not necessarily with
the same sound), it could be there's something wrong with the power
you're feeding to it.

Do you use some kind of voltage regulator between your wall outlet and
the computer ? That, perhaps your UPS, could be malfunctioning and
supplying an abnormally high voltage.

Is it possible you're using a PSU for an American 110-volt system in
your 240-volt UK line ? Now pls don't feel insulted by that - I'm just
exploring theoretical possibilities ... . I had a few customers with
itchy fingers who played with the 115/230-volt switch in a
dual-standard product and blew their TVs, tape decks and computer
PSUs.

 

[Al Smith]

Well you don't necessarily need to use every mounting hole. I've seen some

ATX mainboards with nine mounting holes. That's definitely overkill. I've
also found it is not unusual to find a brand new ATX case with standoffs
pre-installed in areas that do NOT match some of your ATX mainboard mounting
holes. Thus, it would be easy to install a mainboard with an extra
standoff. -Dave

It's not a bad idea to use as many mounting holes as you can,
though, to reduce flex in the motherboard. Later, when you are
plugging and unplugging stuff, and it won't come off without lots
of grunting and sweating, you'll be glad to have the motherboard
as stiff as possible.

 

[JJ \(UK\)]

If I may jump in kind of late.

It's never too late!

Was the 'farty bang' you described an
explosive sound accompanied by a 'phfffft' sound ? That sounds very
much like a capacitor venting, probably the main filter capacitors. If
that's the case and it happened a second time (not necessarily with
the same sound), it could be there's something wrong with the power
you're feeding to it.

Do you use some kind of voltage regulator between your wall outlet and
the computer ? That, perhaps your UPS, could be malfunctioning and
supplying an abnormally high voltage.

No. There's no UPS, it's only my home PC for playing Thief Gold and the
like. It runs off a splitter with a few other devices (a zip drive, my PC
speakers, my wife's PC speakers, the monitor) which are all running just
fine.

I had a few customers with
itchy fingers who played with the 115/230-volt switch in a
dual-standard product and blew their TVs, tape decks and computer
PSUs.

Hehe, I can remember doing something like that with my guitar speaker when I
bought it at the age of 18...

JJ (UK)