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