[Tfug] power supplies & motherboards

[Bexley Hall]

Hi Erich,

> I have a vintage 2004 tower that had a power supply failure.
> At least I'm pretty sure it was the power supply: the smell
> of burnt components came from the power supply. The

The expression is:  "I smell amps" (and "amps" must be pronounced
with an Austrian accent!  :> )

> motherboard smells/shows no signs of damage.

<shrug> Doesn't mean anything.  You can toast a component
without it ever showing any outward signs of damage.

> Then I heard a rather disturbing thing in a conversation.
> Power supplies have been known to fail on some models
> of computers and take out the motherboard with them.
> 
>         So I have two questions:
> 
> 1) If a power supply fails, is there a chance that
> it will take out a motherboard?

"Chance"?  Of course!  Actual probability that it will depends
on the design of the motherboard and power supply and the
quality of the components used in each.

Having said that, you probably stand a decent chance of
the motherboard being OK.  If you have a spare power supply,
try it.  (pull as many "other" loads off of the supply
so you don't needlessly subject them to yet another
'dubious' set of circumstances).

Of course, finding the *right* power supply may be an
issue (e.g., they have changed over the years.  And, some
manufacturers have supplies that *look* like "normal"
power supplies but use non standard pinouts -- I got
screwed by a Dell PS one time...)

Even before a PS *noticably* fails, it can "misbehave"
in ways that damage or stress your MB (and anything
else connected to it!).  E.g., if a supply (a voltage)
has bad regulation, then those things on that supply
can be operating outside their intended operating
limits.  I would be more wary of this on newer processors
where you may be running at *2* volts (so, a given
deviation looks like a BIG deviation).

Regardless, I have no qualms about rescuing MB's
with bad caps, etc.  OTOH, if the MB starts behaving
"funny", I don't waste any time trying to diagnose the
"problem" as it can be damn near anything once it has
been operated in this funky set of circumstances.

> 2) If a motherboard is suspected to have failed.
> will it take out a power supply?

Again, possible but usually not.  Most catastrophic failures
manifest as shorts to the power supply -- and the PS is
usually protected against this.  Of course, there are all
sorts of exotic ways that a failure *could* occur that the
supply might not be prepared to handle but they aren't the
norm.

PS's are cheap.  If you just want to test a suspect motherboard,
get a small/cheap one and test *just* the motherboard (this
reduces the requirements that the PS must meet since it
doesn't *also* have to spin up disks, PCI cards, etc.)

Vintage 2004... speed?  You might be able to pick up a $20
special at WorldCare and save yourself the hassle of playing
with yours...