Unbelievable, 'sod's law' - power supply blows

I've had assistance here lately with my Deskpro EN SFF 886. I had
been ignoring a sound like the hard drive switching itself on and off
for a little while now and tonight it sems the power supply has
blown. There was a small pop and a smell of burning and the green
light's out for good, with a fuse change in the plug doing nothing. I
can see a new supply will cost more than the machine, and there are no
used ones on ebay at the moment that fit. I will asks the
refurbishers to replace it but they are dodgy dealers who don't answer
emails and I don't expect to get anywhere.

I see there are 'no user-serviceable parts' inside these power
supplies - haven't they got a simple fuse in to replace? - and I've
heard rightly or wrongly that it's dangerous to open power supplies.
But, is is likely that the power supply blowing has taken anything out
with it? Like killing the motherboard? Because I've thought of
moving the hard drive, RAM, DVD rom drive and floppy drive to
something else, there being a few shops a short walk away that have
used and custom systems. What do you think? Should I be hopeful (I
will see if they have salvaged the same power supply first).

I was in the middle of giving the machine a new lease of life by
installing Linux Mint 2.2 (an Ubuntu derivative from only a few years
back that suited the spec very well), which looked good when viewing
the live CD and would get me round the problem of not being able to
use smooth fonts after much googling and experimentation, so I am
peeved after getting round a few problems with this machine that it
has blown. Worse, a cheque I've been waiting for for sixteen months
arrived this morning and is now probably earmarked for other things...
sigh.

Thanks in advance for any opinions, advice, suggestions, non-malicious
laughter, etc.

poachedeggs wrote:
I've had assistance here lately with my Deskpro EN SFF 886. I had
been ignoring a sound like the hard drive switching itself on and off
for a little while now and tonight it sems the power supply has
blown. There was a small pop and a smell of burning and the green
light's out for good, with a fuse change in the plug doing nothing. I
can see a new supply will cost more than the machine, and there are no
used ones on ebay at the moment that fit. I will asks the
refurbishers to replace it but they are dodgy dealers who don't answer
emails and I don't expect to get anywhere.

I see there are 'no user-serviceable parts' inside these power
supplies - haven't they got a simple fuse in to replace? - and I've
heard rightly or wrongly that it's dangerous to open power supplies.
But, is is likely that the power supply blowing has taken anything out
with it? Like killing the motherboard? Because I've thought of
moving the hard drive, RAM, DVD rom drive and floppy drive to
something else, there being a few shops a short walk away that have
used and custom systems. What do you think? Should I be hopeful (I
will see if they have salvaged the same power supply first).

I was in the middle of giving the machine a new lease of life by
installing Linux Mint 2.2 (an Ubuntu derivative from only a few years
back that suited the spec very well), which looked good when viewing
the live CD and would get me round the problem of not being able to
use smooth fonts after much googling and experimentation, so I am
peeved after getting round a few problems with this machine that it
has blown. Worse, a cheque I've been waiting for for sixteen months
arrived this morning and is now probably earmarked for other things...
sigh.

Thanks in advance for any opinions, advice, suggestions, non-malicious
laughter, etc.

The usual replacement for a power supply is another power supply. A few
years ago, I opened up a custom power supply and replaced its fan,
because Compaq (or a 3rd party parts house) would charge over $US100 for
one... Ben Myers

Hi!

There was a small pop and a smell of burning and the green
light's out for good, with a fuse change in the plug doing nothing.

In a word, "oops".

Changing the fuse won't fix it--you've probably lost one of the switching
transistors in the power supply.

It's probably time to start looking for another system.

I see there are 'no user-serviceable parts' inside these power
supplies - haven't they got a simple fuse in to replace?

Yes and no. I'm sure there is a protective fuse in the supply itself, or
something very similar in function. But the fuse isn't what will be wrong,
and replacing may only lead to more spectacular failures. You need to find
out why the fuse blew. Some of this will be obvious--burnt and obliterated
parts will show up. What caused those parts to fail may not be easy to find,
as the truly defective part may not have blown up.

As to the no-user-serviceable parts...well, the parts inside are serviceable
if you can find replacements and know how to solder without making a mess
and hurting yourself. You might actually stand a pretty fair chance of
getting parts like capacitors, diodes and maybe even the main switching
transistors. If you've lost a transformer, some coils, strange looking
unmarked parts that you have no idea what they are, or the controller IC is
fried...then you're probably out of luck. PC power supplies aren't
particularly easy to fix, mainly because service literature isn't usually
available in detailed enough form. Compaq most likely replaced these
supplies as a whole unit and I doubt they ever did any repairs on bad ones
that came back. If you have some experience, can find the controller IC
datasheet, don't mind spending a few bucks on the most likely to be bad
parts and can accept the fact that you might not be able to fix it...sure,
why not? Should you try to fix it, don't go plugging it into the computer to
test it. Rig up a dummy load that is made of things you won't feel bad about
if they get blown up!

There's not much to be afraid of in a dead PSU, so long as it isn't plugged
in. You can certainly look inside without hurting yourself. The only thing
to really be careful of are the (usually two) main filter capacitors in the
supply. They can hold a charge, although it should dissipate within a few
hours to a few days.

But, is is likely that the power supply blowing has taken anything out
with it? Like killing the motherboard? Because I've thought of
moving the hard drive, RAM, DVD rom drive and floppy drive to
something else, there being a few shops a short walk away that have
used and custom systems. What do you think?

PC power supplies are supposed to shut down (hopefully nonviolently!) in the
event of a fault. They have controllers inside that should see to this, if
they've been properly designed and specified. This doesn't always
happen--sometimes because the power supply was poorly designed, and
sometimes because the failure was so catastrophic that nothing would have
stopped other parts from being fried. In all likelihood, the remaining parts
you have are fine. I wouldn't be surprised if the system came right back to
life immediately with a replacement power supply.

William

I don't know dangerous this was, but a visitor just now says the pink
voltage switch on the psu isn't in the right position and then pointed
at my very long guitar nails. Could I have knocked it with them while
replacing the cord, we wonder in mild horror. In which case, maybe
the rest of the pc's fine? I've been looking at generic power
supplies, though their wattage is two or three times higher - are
these no good? Some are very affordable to me, ten quid. Is the odd
size of the Compaq EN SFF a factor or should a generic one fit?

Thanks for more feedback you two. (I've naively or otherwise asked in
a pc-building group about whether I can transplant everything into a
new case/psu too.)


On Dec 17, 12:30*am, "William R. Walsh"
m wrote:
Hi!

There was a small pop and a smell of burning and the green
light's out for good, with a fuse change in the plug doing nothing.

In a word, "oops".

Changing the fuse won't fix it--you've probably lost one of the switching
transistors in the power supply.

It's probably time to start looking for another system.

I see there are 'no user-serviceable parts' inside these power
supplies - haven't they got a simple fuse in to replace?

Yes and no. I'm sure there is a protective fuse in the supply itself, or
something very similar in function. But the fuse isn't what will be wrong,
and replacing may only lead to more spectacular failures. You need to find
out why the fuse blew. Some of this will be obvious--burnt and obliterated
parts will show up. What caused those parts to fail may not be easy to find,
as the truly defective part may not have blown up.

As to the no-user-serviceable parts...well, the parts inside are serviceable
if you can find replacements and know how to solder without making a mess
and hurting yourself. You might actually stand a pretty fair chance of
getting parts like capacitors, diodes and maybe even the main switching
transistors. If you've lost a transformer, some coils, strange looking
unmarked parts that you have no idea what they are, or the controller IC is
fried...then you're probably out of luck. PC power supplies aren't
particularly easy to fix, mainly because service literature isn't usually
available in detailed enough form. Compaq most likely replaced these
supplies as a whole unit and I doubt they ever did any repairs on bad ones
that came back. If you have some experience, can find the controller IC
datasheet, don't mind spending a few bucks on the most likely to be bad
parts and can accept the fact that you might not be able to fix it...sure,
why not? Should you try to fix it, don't go plugging it into the computer to
test it. Rig up a dummy load that is made of things you won't feel bad about
if they get blown up!

There's not much to be afraid of in a dead PSU, so long as it isn't plugged
in. You can certainly look inside without hurting yourself. The only thing
to really be careful of are the (usually two) main filter capacitors in the
supply. They can hold a charge, although it should dissipate within a few
hours to a few days.

But, is is likely that the power supply blowing has taken anything out
with it? *Like killing the motherboard? *Because I've thought of
moving the hard drive, RAM, DVD rom drive and floppy drive to
something else, there being a few shops a short walk away that have
used and custom systems. *What do you think?

PC power supplies are supposed to shut down (hopefully nonviolently!) in the
event of a fault. They have controllers inside that should see to this, if
they've been properly designed and specified. This doesn't always
happen--sometimes because the power supply was poorly designed, and
sometimes because the failure was so catastrophic that nothing would have
stopped other parts from being fried. In all likelihood, the remaining parts
you have are fine. I wouldn't be surprised if the system came right back to
life immediately with a replacement power supply.

William

poachedeggs wrote:
I don't know dangerous this was, but a visitor just now says the pink
voltage switch on the psu isn't in the right position and then pointed
at my very long guitar nails. Could I have knocked it with them while
replacing the cord, we wonder in mild horror. In which case, maybe
the rest of the pc's fine? I've been looking at generic power
supplies, though their wattage is two or three times higher - are
these no good? Some are very affordable to me, ten quid. Is the odd
size of the Compaq EN SFF a factor or should a generic one fit?

Thanks for more feedback you two. (I've naively or otherwise asked in
a pc-building group about whether I can transplant everything into a
new case/psu too.)


SNIP

Well, if the voltage setting was incorrect, then the PSU was receiving
220-240v when it was expecting 110-120v. That would burn it out for
sure, and with double the voltage, I do not hold much hope for the
motherboard either. The Compaq EN SFF uses a VERY much custom PSU.
Different shape and different power connector than the usual 20-pin ATX
PSU used with a Pentium 3... Ben Myers

On Dec 16, 8:17*pm, poachedeggs wrote:
I don't know dangerous this was, but a visitor just now says the pink
voltage switch on the psu isn't in the right position and then pointed
at my very long guitar nails. *Could I have knocked it with them while
replacing the cord, we wonder in mild horror. *

If a switch was in 220, then a 220 supply was only getting 120
volts. That would not harm the supply; would only cause a supply to
not power. 120 volts does not harm 220 volt electronics. However, if
the switch was changed when the supply was connected to AC mains, then
damage may result.

Switch is not easily changed by accident.

If smoke came out, a fuse will not correct the defect.

Hi!

Could I have knocked it with them while replacing
the cord, we wonder in mild horror. In which case,
maybe the rest of the pc's fine?

Such a mishap would be unlikely, but possible. The voltage selector
switches are generally not that easy to move. The number that is
visible should be the voltage that the supply is set to operate on.

If the supply was set to 110/120 volts and got 220/240, then the
results are usually impressive and the supply will be burnt.

Chances for survival are much better if the supply was set to 220/240
and got 110/120 volts, although I have seen one supply die from that
in a PS/2 Model 25 286 some years back.

I've been looking at generic power supplies, though
their wattage is two or three times higher - are
these no good?

If they're truly capable of the specified wattage, they'll be fine.
(See below.) However, the Compaq Deskpro SFF systems do not use a
standard ATX connector.

You might get it running if you can figure out the pinout and splice
wires, but the PSU you find probably won't fit in the case (unless you
get a small one, which can be done). It would have been much easier to
do this with the power supply working, although wire color can
sometimes give a hint.

Some are very affordable to me, ten quid.

You should look for something better. Let's see what a cheap power
supply looks like inside:

http://greyghost.mooo.com/psuthoughts/

(I've naively or otherwise asked in a pc-building
group about whether I can transplant everything
into a new case/psu too.)

I don't think it will work...the fullsize Deskpro parts might make the
transition because they are more or less ATX shaped. The Deskpro SFF
parts are engineered to work in just one case--the Deskpro SFF case.
They're not a standard shape or size.

If you want to build a computer at a low cost, I would recommend
looking at an inexpensive case and something like the motherboards I
reviewed in the links below if you don't need lots and lots of
computing power:

http://greyghost.mooo.com/intelatom/
http://greyghost.mooo.com/d201gly2/

The current generation of the Intel D945GCLF2 board is the D945GCLF2,
which has an improved processor. I bought one recently. I still need
to review it.

William

William R. Walsh wrote:
Hi!

Could I have knocked it with them while replacing
the cord, we wonder in mild horror. In which case,
maybe the rest of the pc's fine?

Such a mishap would be unlikely, but possible. The voltage selector
switches are generally not that easy to move. The number that is
visible should be the voltage that the supply is set to operate on.

If the supply was set to 110/120 volts and got 220/240, then the
results are usually impressive and the supply will be burnt.

Chances for survival are much better if the supply was set to 220/240
and got 110/120 volts, although I have seen one supply die from that
in a PS/2 Model 25 286 some years back.

I've been looking at generic power supplies, though
their wattage is two or three times higher - are
these no good?

If they're truly capable of the specified wattage, they'll be fine.
(See below.) However, the Compaq Deskpro SFF systems do not use a
standard ATX connector.

You might get it running if you can figure out the pinout and splice
wires, but the PSU you find probably won't fit in the case (unless you
get a small one, which can be done). It would have been much easier to
do this with the power supply working, although wire color can
sometimes give a hint.

Some are very affordable to me, ten quid.

You should look for something better. Let's see what a cheap power
supply looks like inside:

http://greyghost.mooo.com/psuthoughts/

(I've naively or otherwise asked in a pc-building
group about whether I can transplant everything
into a new case/psu too.)

I don't think it will work...the fullsize Deskpro parts might make the
transition because they are more or less ATX shaped. The Deskpro SFF
parts are engineered to work in just one case--the Deskpro SFF case.
They're not a standard shape or size.

If you want to build a computer at a low cost, I would recommend
looking at an inexpensive case and something like the motherboards I
reviewed in the links below if you don't need lots and lots of
computing power:

http://greyghost.mooo.com/intelatom/
http://greyghost.mooo.com/d201gly2/

The current generation of the Intel D945GCLF2 board is the D945GCLF2,
which has an improved processor. I bought one recently. I still need
to review it.

William

Surprise! Some of the desktop models of the Compaq Socket 370 DeskPros
use a custom 24-pin power supply, a forerunner of the newer 24-pinners,
no doubt. Standard ATX size, though.

If someone is really in love with a Compaq DeskPro desktop case, I
suppose another motherboard could be put inside, along with another
power supply and a rewiring of the leads to the front panel (on-off
switch, power LED, HDD LED). It's not a bad looking case, but beige has
fallen out of favor lately... Ben Myers

Hi!

Surprise! Some of the desktop models of the Compaq
Socket 370 DeskPros use a custom 24-pin power supply,
a forerunner of the newer 24-pinners, no doubt.

I wasn't sure, but I figured something like that might be happening.
Still, I'd have to think (and maybe one of these days I'll find out)
that a person inclined to take the time could rearrange the pins in a
standard ATX supply to make it work. Compaq couldn't have been too
creative with the voltages.

If someone is really in love with a Compaq DeskPro
desktop case

It's a nice case...they actually used fairly decent steel for it. The
SFF Deskpro systems are not quite as sturdy, but they'll do. I see
things getting cheaper (thinner metal) into the Evo D500 and D510 SFF
boxen, up to the later "HPaq" models where they became almost totally
generic.

I got a Compaq Presario S4020WM tower that came to me with a blown
Bestec PSU and motherboard. It seemed like too nice of a case to throw
away, so I slapped a Biostar P4M900-M4 motherboard and a Socket 478
Northwoods P4 into it along with a working power supply. It needed
some wiring adaptation for the power LED, HDD LED and the power button
to be functional.

William