Can ATX PSU blow the mainboard?

Can an overheating ATX PSU blow the mainboard if the PSU fails?

I may be mistaken but ISTR there's a possibility of a voltage surge when
the PSU goes.

On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote:

Can an overheating ATX PSU blow the mainboard if the PSU fails?

I may be mistaken but ISTR there's a possibility of a voltage surge when
the PSU goes.

A good one should not. But then even a good one that's been overheated
for too long may no longer be any good. And a bad one could do
anything.

So it's certainly possible. Get a new PSU and see if the machine comes
back up. If not, it's time to spend more money.

Cheers - Jaimie
--
The physics and scientific approach of Armageddon was criticized for its
poor adherence to the laws of physics. This has led NASA to show the
film as part of its management training program. Prospective managers
are asked to find as many inaccuracies in the movie as they can.

On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote:

Can an overheating ATX PSU blow the mainboard if the PSU fails?

I may be mistaken but ISTR there's a possibility of a voltage surge when
the PSU goes.

Apart from the well known infamous Bestec ATX psus used by eMachines
models harking back a decade ago, most ATX PSUs fail without damaging
the MoBo.

The usual failure mode when SMPSUs overheat is for the switching
transistors in the HT module to go short circuit and smash the safety
fuse to smithereens in a flash of light accompanied by a loud pop and
a trace of smoke.

When a PSU shuffles off its mortal coil with such drama, only a
single modest transient voltage spike appears on the voltage rails
(the very small ferrite transformer can only transfer a limited amount
of power due to such a _single_ terminal pulse of current) which is
incapable of causing damage. IOW, the kindest failure mode wrt the
load is that dramatic sudden fuse shattering failure of the switching
transistors in the HT module.

There are other types of failure involving sustained overvoltage but
these tend to be rare unless the manufacturer goes out of his way to
bypass/ignore the overload/overvoltage protection features built into
all the standard smpsu controller chips that made it possible to
manufacture ATX psus at all in large volumes at affordable prices.

If the ATX PSU in question went "BANG!", then it's most likely that
no harm has been done and a drop in replacement ATX PSU will get
things working again.
--
Regards, J B Good

In article , johnny-b-
says...

On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote:

Can an overheating ATX PSU blow the mainboard if the PSU fails?

.... (good stuff) trimmed.

If the ATX PSU in question went "BANG!", then it's most likely that
no harm has been done and a drop in replacement ATX PSU will get
things working again.

An acquaintance brought me a machine which had gone bang in this way
last year. I dropped in a cheap replacement PSU, and it seemed fine. I
left it running overnight. In the morning it was inert. Tested the PSU
- now dead. Tested a second PSU and dropped that in. Still inert.
Tested the second replacement PSU again - dead. This problem was
clearly out of my pay-grade, so sent it to a normally reliable repairer
I'd used before. They said they couldn't fix it - motherboard had gone
- and advised sending it back to the manufacturer (Carillon). They
replaced the motherboard, and also the hard disk, discarding the old
one, along with all my acquaintance's most precious data. Ex-
acquaintance now - he blamed me, and was very unpleasant. I guess I
could have backed up his data for him, but he hadn't, and wanted
everything on the cheap. People often won't pay for the time it takes
to do things properly, and then there's outrage when something goes
wrong (thankfully very rare so far).

Oddly, I've just told a valued customer (valued mainly because he's such
a nice bloke) that I'll do his repair for free now because it's taken so
long to find time to do it. And I realise I'm immediately taking more
precautions (e.g. imaging everything plus data snapshots) because it
won't cost him any more. I'm not cut out for this work...

--

Phil, London

Philip Herlihy wrote:
In article , johnny-b-
says...
On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote:

Can an overheating ATX PSU blow the mainboard if the PSU fails?

... (good stuff) trimmed.
If the ATX PSU in question went "BANG!", then it's most likely that
no harm has been done and a drop in replacement ATX PSU will get
things working again.

An acquaintance brought me a machine which had gone bang in this way
last year. I dropped in a cheap replacement PSU, and it seemed fine. I
left it running overnight. In the morning it was inert. Tested the PSU
- now dead. Tested a second PSU and dropped that in. Still inert.
Tested the second replacement PSU again - dead. This problem was
clearly out of my pay-grade, so sent it to a normally reliable repairer
I'd used before. They said they couldn't fix it - motherboard had gone
- and advised sending it back to the manufacturer (Carillon). They
replaced the motherboard, and also the hard disk, discarding the old
one, along with all my acquaintance's most precious data. Ex-
acquaintance now - he blamed me, and was very unpleasant. I guess I
could have backed up his data for him, but he hadn't, and wanted
everything on the cheap. People often won't pay for the time it takes
to do things properly, and then there's outrage when something goes
wrong (thankfully very rare so far).

Oddly, I've just told a valued customer (valued mainly because he's such
a nice bloke) that I'll do his repair for free now because it's taken so
long to find time to do it. And I realise I'm immediately taking more
precautions (e.g. imaging everything plus data snapshots) because it
won't cost him any more. I'm not cut out for this work...


If you plan to repair a lot of PCs, I recommend a couple things.

1) Everyone should have a multimeter, because you can
get a basic one for $20. And it allows checking
the voltages. So bang for buck, it's a good deal.

Measuring current flow, requires a breakout
cable of some sort - you need to be "in series"
when using one of those, to measure current flow.
Measuring all the rails would take all morning.

2) A second item, more expensive, is a DC clamp-on ammeter.
I can wrap the jaws of that, around wires of the same color
on the main ATX power cable, and make current measurements.
And see whether the load is normal or not. Or whether
the load is really too much for the replacement supply.
There are many AC clamp-on ammeters, but DC capable ones
are fewer in number. The DC ones use a Hall probe for
the measurement.

I got one like this, an Extech, before they got the ugly
color scheme. Mine is grey in color, throughout. For PC
work, the main range of value is the 40A DC range. The 400A
range is good for working on my car (detecting the starter
motor in the car drawing 150A peak current). The thing has
peak hold, so you can find the "worst" loading during
a session if you want. The Hall Probe has a tendency to
wander, so you have to zero it with the zero button on
the front.

http://www.drillspot.com/products/88...clamp_on_meter

It also has AC amps, and I use one of the AC ranges for
working on electric motors. Like the 10A on my 230V
central air conditioner compressor.

That particular meter, isn't sensitive enough to work with
small currents. But for the range a PC might draw,
you can do some service work with one. For example,
on my old AthlonXP system, when running Prime95, I
might see 16A on the +5V rail (because back then, the
processor used to run the switching converter off +5V.
Not all boards did that, but some brands preferred to
use +5V instead of +12V. This was before the ATX12V
cable became popular.

That one claims to have true RMS measurement capability
(probably up to around 50KHz or so), but when attempting
to measure the distorted waveform from a non-PFC power
supply, it does a poor job. I have to conclude it
really isn't True RMS. If you want to measure input power
to the PC with reasonable accuracy, a Kill-O-Watt meter
is good for that, and also, relatively cheap. That's one
tool I don't currently have in my collection - but if one
was sitting in the hardware store, I could not resist an
"impulse buy" if it was available.

Paul

"Jason" wrote in message
...
Can an overheating ATX PSU blow the mainboard if the PSU fails?

I may be mistaken but ISTR there's a possibility of a voltage surge when
the PSU goes.


If it's an Intel based system then it is unlikely but if it is an AMD based
system it could well take the board and processor out with it.
--

Cheers
Niel H

On Thu, 31 Oct 2013 12:35:14 -0400, Paul wrote:

Philip Herlihy wrote:
In article , johnny-b-
says...
On Wed, 30 Oct 2013 21:23:54 GMT, Jason wrote:

Can an overheating ATX PSU blow the mainboard if the PSU fails?

... (good stuff) trimmed.
If the ATX PSU in question went "BANG!", then it's most likely that
no harm has been done and a drop in replacement ATX PSU will get
things working again.

An acquaintance brought me a machine which had gone bang in this way
last year. I dropped in a cheap replacement PSU, and it seemed fine. I
left it running overnight. In the morning it was inert. Tested the PSU
- now dead. Tested a second PSU and dropped that in. Still inert.
Tested the second replacement PSU again - dead. This problem was
clearly out of my pay-grade, so sent it to a normally reliable repairer
I'd used before. They said they couldn't fix it - motherboard had gone
- and advised sending it back to the manufacturer (Carillon). They
replaced the motherboard, and also the hard disk, discarding the old
one, along with all my acquaintance's most precious data. Ex-
acquaintance now - he blamed me, and was very unpleasant. I guess I
could have backed up his data for him, but he hadn't, and wanted
everything on the cheap. People often won't pay for the time it takes
to do things properly, and then there's outrage when something goes
wrong (thankfully very rare so far).

Oddly, I've just told a valued customer (valued mainly because he's such
a nice bloke) that I'll do his repair for free now because it's taken so
long to find time to do it. And I realise I'm immediately taking more
precautions (e.g. imaging everything plus data snapshots) because it
won't cost him any more. I'm not cut out for this work...


If you plan to repair a lot of PCs, I recommend a couple things.

1) Everyone should have a multimeter, because you can
get a basic one for $20. And it allows checking
the voltages. So bang for buck, it's a good deal.

+1 but it can't indicate high ripple and switching noise of course.


Measuring current flow, requires a breakout
cable of some sort - you need to be "in series"
when using one of those, to measure current flow.
Measuring all the rails would take all morning.

2) A second item, more expensive, is a DC clamp-on ammeter.
I can wrap the jaws of that, around wires of the same color
on the main ATX power cable, and make current measurements.
And see whether the load is normal or not. Or whether
the load is really too much for the replacement supply.
There are many AC clamp-on ammeters, but DC capable ones
are fewer in number. The DC ones use a Hall probe for
the measurement.

I got one like this, an Extech, before they got the ugly
color scheme. Mine is grey in color, throughout. For PC
work, the main range of value is the 40A DC range. The 400A
range is good for working on my car (detecting the starter
motor in the car drawing 150A peak current). The thing has
peak hold, so you can find the "worst" loading during
a session if you want. The Hall Probe has a tendency to
wander, so you have to zero it with the zero button on
the front.

I acquired a similar unit with 1200 and 200 A DC ranges. Despite the
high ranges, its saving grace for this sort of work was the fact that
it had a 4 digit display so could resolve to 0.1A.

The need for a zeroing button is an inherent feature of these DC
clamp meters. I just had a swift look at mine and it was showing
-127.4 A reading until I zeroed it. Even then I had to re-zero it
another 3 or 4 times before it stabilised.

This is something to watch out for when taking readings since you
have to double check the zeroing every few minutes to be sure your
reading is still valid if you need the accuracy to ascertain the total
DC power consumption to get a reasonably good idea of the PSU's
efficiency (when you've got a trustworthy AC watt meter to check the
mains input power).


http://www.drillspot.com/products/88...clamp_on_meter

It also has AC amps, and I use one of the AC ranges for
working on electric motors. Like the 10A on my 230V
central air conditioner compressor.

That particular meter, isn't sensitive enough to work with
small currents. But for the range a PC might draw,
you can do some service work with one. For example,
on my old AthlonXP system, when running Prime95, I
might see 16A on the +5V rail (because back then, the
processor used to run the switching converter off +5V.
Not all boards did that, but some brands preferred to
use +5V instead of +12V. This was before the ATX12V
cable became popular.

That one claims to have true RMS measurement capability
(probably up to around 50KHz or so), but when attempting
to measure the distorted waveform from a non-PFC power
supply, it does a poor job. I have to conclude it
really isn't True RMS. If you want to measure input power
to the PC with reasonable accuracy, a Kill-O-Watt meter
is good for that, and also, relatively cheap. That's one
tool I don't currently have in my collection - but if one
was sitting in the hardware store, I could not resist an
"impulse buy" if it was available.


Yep, the good ol' trustworthy Kill-A-Watt can be really useful to
check for unusually high (fault) loadings. I've got a couple of the
European versions and I'm quite impressed at their accuracy (compared
to some very early "Consumption Meters" I had the misfortune to buy
about 8 or 9 years ago). I have a MetraWatt analogue watt meter which
I bought a couple of decades ago which I use as the benchmark of
accuracy by which to assess these 'New Fangled' digital watt meters.

I'd certainly recommend you buy yourself an AC watt meter since this
can often provide all the information you need to assess what's going
on with a non-booting / no video display system. It's also handy to
avoid MoBo burnout when testing a box full of 2nd user CPUs for
shorted chips. :-)

--
Regards, J B Good

Niel Humphreys wrote:
"Jason" wrote in message
...
Can an overheating ATX PSU blow the mainboard if the PSU fails?

I may be mistaken but ISTR there's a possibility of a voltage surge when
the PSU goes.


If it's an Intel based system then it is unlikely but if it is an AMD based
system it could well take the board and processor out with it.

I have to ask, what makes one more "prone" than the other ?

I haven't any first-hand experience with the problematic
Bestec, but I understand that one, damages a computer
because the +5V output goes to around +8V and damages
all the hardware in the system that uses +5V.

In the case of a "voltage surge", as proposed, the processor
has a switching converter (VCore) located around the
CPU socket. The switching converter provides conversion
and a degree of isolation, between +12V coming into it,
and the approximately +1V feeding the core of the processor.
And that is proposed as a protection mechanism for the
processor - the existence of another power conversion
stage. A few of the motherboard subsystems are like that,
having onboard regulation which can provide some
protection. The motherboard could still blow out,
if a voltage shoots high enough, but it doesn't
really matter what brand of CPU when that happens.
You will likely get to reuse your CPU and RAM,
as they're not directly exposed.

It would be nice to know a proposed mechanism for
this difference between Intel and AMD systems.

Paul

"Paul" wrote in message
...
Niel Humphreys wrote:
"Jason" wrote in message
...
Can an overheating ATX PSU blow the mainboard if the PSU fails?

I may be mistaken but ISTR there's a possibility of a voltage surge when
the PSU goes.


If it's an Intel based system then it is unlikely but if it is an AMD
based system it could well take the board and processor out with it.

I have to ask, what makes one more "prone" than the other ?


It would be nice to know a proposed mechanism for
this difference between Intel and AMD systems.


Intel CPUs have built in heat/voltage protection, AMD processors do not
which is why AMDs tend to be cheaper.

For instance, when the cooling protection fails on an Intel CPU it just
slows down and grinds to a halt until it cools down then works fine again.
With AMD they just fry and usually take the motherboard with them. The same
for voltage spikes etc.

--

Cheers
Niel H

On Fri, 01 Nov 2013 08:31:24 +0000, Niel Humphreys wrote:

It would be nice to know a proposed mechanism for this difference
between Intel and AMD systems.


Intel CPUs have built in heat/voltage protection, AMD processors do not
which is why AMDs tend to be cheaper.

For instance, when the cooling protection fails on an Intel CPU it just
slows down and grinds to a halt until it cools down then works fine
again. With AMD they just fry and usually take the motherboard with
them. The same for voltage spikes etc.

That might have been true about 10 years ago but not now. All AMD CPUs
since the Athlon64 have on-die thermal protection.

--
Tony
'09 FJR1300, '87 TW200,
89 TW200, '07 Street Triple OMF#24