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Hello. I turned on my desktop the other day and it shut off and then I
noticed a puff of smoke and a bad smell. I thought the power supply burned
out even though it was only 3 months old. I went out and bought another one
exactly like the other one and installed it and the same thing happened. I
know now the smoke came off the motherboard. I saw it the second time. Do
you think that the motherboard problem has destroyed both power supplies? I
plugged them directly into the wall hoping to see the fan turn but nothing
happened. Should the fan turn when plugged straight into the wall and does
that mean that the power supplies are both shot now? Thanks.

Thomas

Thomas wrote:
> Hello. I turned on my desktop the other day and it shut off and then I
> noticed a puff of smoke and a bad smell. I thought the power supply burned
> out even though it was only 3 months old. I went out and bought another one
> exactly like the other one and installed it and the same thing happened. I
> know now the smoke came off the motherboard. I saw it the second time. Do
> you think that the motherboard problem has destroyed both power supplies? I
> plugged them directly into the wall hoping to see the fan turn but nothing
> happened. Should the fan turn when plugged straight into the wall and does
> that mean that the power supplies are both shot now? Thanks.
>
> Thomas
>
>

The power supply will not run, when it is sitting all by itself
on your table top. To run, you have to connect PS_ON# to COM,
on the main power connector. That is what the motherboard does,
when the motherboard wants the power supply to turn on. When
PS_ON# is connected to COM (ground), that causes all the
"soft power" voltages to operate, and the power supply fan
to spin.

The power supply does have a standby voltage, called +5VSB, and
that is a source of power for when the computer is sleeping.
It is present as long as the switch on the back is set to ON.
It also powers the circuit that handles switching on the rest
of the power supply. On an Asus motherboard, that is what makes
the green LED on the motherboard surface, to glow.

To test a power supply, you can use a gadget like this, as it
puts a small load on the supply, and connects PS_ON# to COM.
In addition to one of these, a multimeter (available at Radio Shack
or the hardware store), can be used to verify the voltages on the
main connector. That is to help assure you the supply is really
working. Check to see if the +3.3V, +5V, +12V, -12V, +5VSB, are
all operating properly or not.

http://www.startech.com/Product/Item...PSUTEST20&c=CA

Pinout for ATX is here. 24 pin and 20 pin types.

http://www.formfactors.org/developer...public_br2.pdf
http://www.formfactors.org/developer...X12V_1_3dg.pdf

Paul

"Paul" <> wrote in message news:fjl5cd$geg$...
> Thomas wrote:
>> Hello. I turned on my desktop the other day and it shut off and then I
>> noticed a puff of smoke and a bad smell. I thought the power supply
>> burned out even though it was only 3 months old. I went out and bought
>> another one exactly like the other one and installed it and the same
>> thing happened. I know now the smoke came off the motherboard. I saw it
>> the second time. Do you think that the motherboard problem has destroyed
>> both power supplies? I plugged them directly into the wall hoping to see
>> the fan turn but nothing happened. Should the fan turn when plugged
>> straight into the wall and does that mean that the power supplies are
>> both shot now? Thanks.
>>
>> Thomas
>
> The power supply will not run, when it is sitting all by itself
> on your table top. To run, you have to connect PS_ON# to COM,
> on the main power connector. That is what the motherboard does,
> when the motherboard wants the power supply to turn on. When
> PS_ON# is connected to COM (ground), that causes all the
> "soft power" voltages to operate, and the power supply fan
> to spin.
>
> The power supply does have a standby voltage, called +5VSB, and
> that is a source of power for when the computer is sleeping.
> It is present as long as the switch on the back is set to ON.
> It also powers the circuit that handles switching on the rest
> of the power supply. On an Asus motherboard, that is what makes
> the green LED on the motherboard surface, to glow.
>
> To test a power supply, you can use a gadget like this, as it
> puts a small load on the supply, and connects PS_ON# to COM.
> In addition to one of these, a multimeter (available at Radio Shack
> or the hardware store), can be used to verify the voltages on the
> main connector. That is to help assure you the supply is really
> working. Check to see if the +3.3V, +5V, +12V, -12V, +5VSB, are
> all operating properly or not.
>
> http://www.startech.com/Product/Item...PSUTEST20&c=CA
>
> Pinout for ATX is here. 24 pin and 20 pin types.
>
> http://www.formfactors.org/developer...public_br2.pdf
> http://www.formfactors.org/developer...X12V_1_3dg.pdf
>
> Paul

The fans do not run when the power supply is plugged into the wall. The
computer sends an ON signal to the power supply to get a visible ON
condition, otherwise you can not see the power supply operating.

I'm not sure the power supply is toast, but the magic smoke leaking from the
motherboard is never a good sign. Computers work by magic smoke, and yours
has leaked out so I do not hold much hope for it to work again.



"Thomas" <> wrote in message
news:Kno7j.6727$...
> Hello. I turned on my desktop the other day and it shut off and then I
> noticed a puff of smoke and a bad smell. I thought the power supply
> burned out even though it was only 3 months old. I went out and bought
> another one exactly like the other one and installed it and the same thing
> happened. I know now the smoke came off the motherboard. I saw it the
> second time. Do you think that the motherboard problem has destroyed both
> power supplies? I plugged them directly into the wall hoping to see the
> fan turn but nothing happened. Should the fan turn when plugged straight
> into the wall and does that mean that the power supplies are both shot
> now? Thanks.
>
> Thomas
>