power supply unit fryed?

[jacky]

Hello I'm wondering if anyone can help.
I know someone whose computer suddenly stopped working. There was nothing
when she switched it on. No fan sound from the power supply, no LED's it was
completely dead. She took it to PC world and they suggested it was the Power
Supply that had gone.
Now this is all well and good. But they tried another power supply unit and
they said that the computer blew this new unit and it would be very
expensive to repair the system
Is this possible and can anyone suggest a possible cause. I mean all the
components of a PC are all low voltage and it was working fine before. What
could have gone wrong with it to destroy a power unit?
I should point out that the day before it died. It refused to boot up
without any fan sounds but the owner fiddled with the cables at the back to
make sure they were all firmly attached and it started working again.
The power supply and motherboard are ATX types and I live in the UK where
the mains voltage is 240v.
Thanks.

 

[w_tom]

If PSU unit is destroyed, then PSU is defective by design.
Intel even says how big a wire must short all outputs together
and still a PSU cannot fail. If the new PSU was damaged by
computer, then run. The repairman does not even have basic
knowledge. Many repairmen only know to keep replacing
components until something works. Many repairmen don't even
know of other essential functions that are suppose to be
included in a power supply.

 

[JAD]

Here's the one thing that I can tell you with no doubt, There
definitely are things that can fail on a mainboard that can 'kill' a
power supply.
That being said, here are some speculations. Some older mainboards had
power circuit 'issues' involving a batch of bad capacitors. Without
going into the 'engineering' explanation of it, suffice it to say that
they leaked and bulged at the top. You could inspect the board for
this scenario. Good place to start would be around the power connector
for the power supply or around the CPU.

Try removing all the hardware except the video card - Powersupply(if
you can get one)
-cpu and -1 stick of memory and power up.
(or ask the techs if they did this already) if they did then the odds
are higher
that the mainboard is broken.

good luck

 

[Harry]

Hello I'm wondering if anyone can help.
I know someone whose computer suddenly stopped working. There was nothing
when she switched it on. No fan sound from the power supply, no LED's it was
completely dead. She took it to PC world and they suggested it was the Power
Supply that had gone.
Now this is all well and good. But they tried another power supply unit and
they said that the computer blew this new unit and it would be very
expensive to repair the system

I think that this is a way of them saying "lets replace the
motherboard and bits, cos we havent a clue!"

Unless they can give a proper reason why it will be expensive, I would
take it to an independant computer retailer. For a start PCWorld have
the unenviable reputation for being a bit thick when it comes to PCs.

Is this possible and can anyone suggest a possible cause. I mean all the
components of a PC are all low voltage and it was working fine before. What
could have gone wrong with it to destroy a power unit?

Power Supplys can fail for no reason at all. A quality Power Supply
will last for ages (I have been using a 300W supply for 3 years now)
but a cheap one might only last a few months.

I should point out that the day before it died. It refused to boot up
without any fan sounds but the owner fiddled with the cables at the back to
make sure they were all firmly attached and it started working again.

Could it just be a dodgy power lead from the mains socket to the PC?
Did they test the PC with the power lead from the PC or did they use
their own power lead.

If you have a spare power lead, or can borrow one from another PC,
then try that first.

 

[jacky]

I think that this is a way of them saying "lets replace the
motherboard and bits, cos we havent a clue!"

Unless they can give a proper reason why it will be expensive, I would
take it to an independant computer retailer. For a start PCWorld have
the unenviable reputation for being a bit thick when it comes to PCs.

Power Supplys can fail for no reason at all. A quality Power Supply
will last for ages (I have been using a 300W supply for 3 years now)
but a cheap one might only last a few months.
Could it just be a dodgy power lead from the mains socket to the PC?
Did they test the PC with the power lead from the PC or did they use
their own power lead.

If you have a spare power lead, or can borrow one from another PC,
then try that first.

Hello. They've bought a new computer and I've got this old one.
I'm in no particular hurry, but I'll buy a new power supply and try it
rather than throwing it away because if its cheap and easy to repair it can
be used again.
I suspect that the front power switch might be broken. Not the power switch
on the back, which is part of the power supply, but the motherboard power
switch. If that's not working then the whole computer won't switch on.
The hard drive is okay as I hooked it up as a slave in another system and
transferred some of the data.

 

[Peter Ives]

Hello I'm wondering if anyone can help.
I know someone whose computer suddenly stopped working. There was
nothing
when she switched it on. No fan sound from the power supply, no LED's it
was
completely dead. She took it to PC world and they suggested it was the
Power
Supply that had gone.
Now this is all well and good. But they tried another power supply unit and
they said that the computer blew this new unit and it would be very
expensive to repair the system
Is this possible and can anyone suggest a possible cause. I mean all the
components of a PC are all low voltage and it was working fine before. What
could have gone wrong with it to destroy a power unit?
I should point out that the day before it died. It refused to boot up
without any fan sounds but the owner fiddled with the cables at the back to
make sure they were all firmly attached and it started working again.
The power supply and motherboard are ATX types and I live in the UK
where
the mains voltage is 240v.
Thanks.

If you have the confidence you could test the power supply yourself.
It's reasonably simple to do and involves shorting 2 of the wires from
the ATX motherboard plug together. Are you up for it?

One other thing, when a power supply does blow (though there's no
indication from what you say that it blew as such, it may well have just
died) it doesn't necessarily mean that the motherboard and components
have gone up in smoke with it.

 

[w_tom]

Don't foolishly replace parts only because you like betting
on horses. Procedure to make a defective system functional is
so simple and too often not performed in repair shops. For
starters, a power supply system involves three sections: PSU,
motherboard controller circuit, and power switch. Which is
defective or how to identify the repairman who knows basic
electrical concepts? He starts with the so ubiquitous and so
inexpensive 3.5 digit multimeter. Problem identified in
seconds. Procedure to determine which (of three) is defective
is posted as: "I think my power supply is dead" in
alt.comp.hardware on 5 Feb 2004 at
http://www.tinyurl.com\2musa or in
alt.comp.hardware.pc-homebuilt entitled "Power Supply" on 5
Feb 2004 at http://tinyurl.com/32j4g .

New power supply? If buying one for $40, then PSU is
probably missing many internal functions that were even
defacto standard 30 years ago. Again, too many repairman
don't even know what those functions are - which is just one
reason why some motherboards can damage a power supply or a
PSU can damage disk drives.

A painfully simple concept. First identify reason for
failure or at least use numbers to have good reason why to
suspect something. IOW first collect data. Only after does
one fix the problem. Problems are solved the first time.
People learn the many functions that must even be performed by
a power supply. Read those two previous posts, get the meter,
and (if nothing else) learn how the system really works.
Don't waste time and money by shotgunning.

 

[w_tom]

Since you can say with "no doubt", then you can report what
on mainboard causes a PSU failure AND why it causes such
damage. If claiming something that even Intel does not say,
then engineering reasons better damn well be provided.
Reasons why a "batch of bad capacitors" on mainboard can kill
a power supply. Using engineering reasons, posted was:

If the new PSU was damaged by computer, then run. The
repairman does not even have basic knowledge.

Please explain, only in engineering terms, how a mainboard
can damage any properly designed power supply?

 

[w_tom]

Let's take your point one step further. If power supply
failure does damage motherboard and components, then PSU was
missing essential function that was standard even 30 years
ago. One required function is called overvoltage protection
(OVP). OVP may be missing on PSUs marketed only for lesser
computer repairmen. People who fix computers but don't even
know of basic functions required in properly designed power
supplies. How to sell the $70 PSU for $20 or $40? Forget to
include many essential functions and don't provide technical
specifications. One missing function required to protect
motherboard and components is OVP.

Many buy only on the one specification they understand -
price. Such supplies do not provide a long list of electronic
specifications. Why bother? They are not selling to people
with basic technical knowledge. Those $20 and $40 supplies
are being sold to those with a bean counter mentality. People
who repair only by swapping parts until something works.

A properly constructed power supply must not damage a
motherboard. A motherboard and components must not be damaged
even by a failed power supply. This was a defacto standard
long before the PC (and PC repairmen) even existed.

 

[DaveW]

It would pretty much have to be a bad motherboard.

 

[JAD]

right tom.....its never happened before I could I have been so
foolish to think a mainboard with a shorted power terminal, cause a
bit of metal had fallen down behind the plate and the PCB and took out
the 12v source.,,,I will not get into a long boring post using over
priced words....I did not say his circumstance fell into the same
category, just said there are thing that can go wrong and take out
the power supply. Not going to spit hairs between what a 'properly'
designed power supply is and what is not....and who has one and who
doesn't.

 

[w_tom]

Even Intel demands that a shorted power supply output not
damage the power supply. But then this was defacto standard
even 30 years ago - that well known even to those with minimal
basic knowledge. JAD has simply demonstrated what happens
when one without technical knowledge buys an inferior power
supply (typically only on price), and then suffers failure.
That inferior supply is proof enough that a mainboard can
damage the supply? Its called first learning how a PSU
works. If a shorted PSU is damaged, then failure is directly
traceable to the human.

Intel even states how big the shorting wire must be -
without any damage to supply. Who do we believe? Intel
requirements, or experience by JAD with inferior supplies that
even the technically competent would not buy?

A mainboard failure must not damage any power supply - which
is why JAD cannot provide an 'engineering explanation' that he
mentioned earlier.

 

[JAD]

anal much?

Even Intel demands that a shorted power supply output not
damage the power supply. But then this was defacto standard
even 30 years ago - that well known even to those with minimal
basic knowledge. JAD has simply demonstrated what happens
when one without technical knowledge buys an inferior power
supply (typically only on price), and then suffers failure.
That inferior supply is proof enough that a mainboard can
damage the supply? Its called first learning how a PSU
works. If a shorted PSU is damaged, then failure is directly
traceable to the human.

Intel even states how big the shorting wire must be -
without any damage to supply. Who do we believe? Intel
requirements, or experience by JAD with inferior supplies that
even the technically competent would not buy?

A mainboard failure must not damage any power supply - which
is why JAD cannot provide an 'engineering explanation' that he
mentioned earlier.

 

[Guest]

I know someone whose computer suddenly stopped working.
There was nothing when she switched it on. No fan sound
from the power supply, no LED's it was completely dead.
She took it to PC world and they suggested it was the Power
Supply that had gone. Now this is all well and good. But
they tried another power supply unit and they said that
the computer blew this new unit and it would be very
expensive to repair the system
Is this possible and can anyone suggest a possible cause.
I mean all the components of a PC are all low voltage and
it was working fine before. What could have gone wrong with
it to destroy a power unit? I should point out that the day
before it died. It refused to boot up without any fan sounds
but the owner fiddled with the cables at the back to make
sure they were all firmly attached and it started working again.

My guess is that playing with the cables did nothing and that the
computer was marginal but finally gave out because of bad electrolytic
capacitors, especially on the part of the motherboard that takes +5V
or +12V from the power supply and converts it down to the CPU core
voltage. But any technician who's even barely competent could have
tested those capacitors and the regulator, although here in the U.S.
the vast majority of people who work on computers for a living aren't
competent.

The most likely reason those power supplies failed was because they
were badly built in the first place, and all supplies are claimed to
be protected against shorts, overloads, and excessive voltage, whether
they really are or not. What are the brands of both supplies? I hope
neither was a Q-tec, Deer (many brands), or Powmax. PC World UK is
rather famous for selling junk.

 

[w_tom]

Insulting others is common among those who did not even
learn basic technical knowledge - learn how electricity
works. JAD thinks a shorted motherboard capacitor will
destroy power supplies - in direct contradiction even to Intel
specifications. Too many who 'replace parts until something
works' actually consider themselves computer 'experts'. JAD
is typically of the "vast majority of people who work on
computers for a living aren't competent". JAD should spend
more time reading and learning; less time posting and
insulting others.

 

[JAD]

tom yada yada yada shall we all cut and paste your long winded
(always correct -never practical -hardly diplomatic) posts.... frankly
your approach to troubleshooting would have me spending hours of time
finding out the obvious. proving which component is responsible within
the PSU, yahoo! that's never been the number one thing on my clients
mind. it serves no purpose when you have countless useable PSU's
about, to plug in and move on. On top of that, most people aren't here
to get an A+ in one component of a computer system.

Some people feel its a compliment to be anal. insulting others is ok
when you hide them in intellectual jargon, eh?

Never said a cap would do anything.... but you read into whatever you
like...
No boot do to a suspected power problem + older board = further
inspection of a known common problem that would prevent a BOOT.


OP<<<<I should point out that the day before it died. It refused to
boot up
without any fan sounds but the owner fiddled with the cables at the
back to
make sure they were all firmly attached and it started working again.



<<<That being said, here are some speculations. Some older mainboards
had
power circuit 'issues' involving a batch of bad capacitors. Without
going into the 'engineering' explanation of it, suffice it to say that
they leaked and bulged at the top. You could inspect the board for
this scenario. Good place to start would be around the power connector
for the power supply or around the CPU.>>>>

Where do you get a CAP will blow your PSU out of this?????????

Take a Midol..