My HTPC is shutting itself down. I am not seeing any side-effects
when rebooting XP Pro, but one characteristic of these relatively
frequent shutdowns is that I cannot simply power up without first
toggling the power supply's own power switch (rear of computer) off/on
-- after which it starts up normally.
What would this PS on/off switch have to do with anything?
Windows XP Pro (Sp2)
Pentium 4 & VIA chipset mobo
ATI Radeon 9700 AIW
In article <1194269416.516072.201000@22g2000hsm.googlegroups. com>,
rarewolf says...
> My HTPC is shutting itself down. I am not seeing any side-effects
> when rebooting XP Pro, but one characteristic of these relatively
> frequent shutdowns is that I cannot simply power up without first
> toggling the power supply's own power switch (rear of computer) off/on
> -- after which it starts up normally.
>
> What would this PS on/off switch have to do with anything?
>
It'll completely kill power to the motherboard whereas the front panel
switch/Windows shutdown basically leaves the computer in a "standby"
state.
"rarewolf" <rarewolf@gmail.com> wrote in message
news:1194269416.516072.201000@22g2000hsm.googlegro ups.com...
> My HTPC is shutting itself down. I am not seeing any side-effects
> when rebooting XP Pro, but one characteristic of these relatively
> frequent shutdowns is that I cannot simply power up without first
> toggling the power supply's own power switch (rear of computer) off/on
> -- after which it starts up normally.
>
> What would this PS on/off switch have to do with anything?
>
> Windows XP Pro (Sp2)
> Pentium 4 & VIA chipset mobo
> ATI Radeon 9700 AIW
>
Just a guess but on your PS power switch may also function as a circuit
breaker reset switch. If so this is not good. I would not operate PC in this
condition until problem is identified. In extreme worst case scenario this
may possibly be a fire hazard.
Good Luck
pcbuilder98
rarewolf wrote:
> My HTPC is shutting itself down. I am not seeing any side-effects
> when rebooting XP Pro, but one characteristic of these relatively
> frequent shutdowns is that I cannot simply power up without first
> toggling the power supply's own power switch (rear of computer) off/on
> -- after which it starts up normally.
>
> What would this PS on/off switch have to do with anything?
>
> Windows XP Pro (Sp2)
> Pentium 4 & VIA chipset mobo
> ATI Radeon 9700 AIW
>
The Vcore regulator on a motherboard, may "latch off" if it detects an
overload. To clear the "latch off" condition, may require removing +5VSB
from the motherboard. When you flip the switch on the power supply, that
removes +5VSB. So a failure to POST, could be a protection feature flipping,
in the Vcore circuit (either for good reason, or not for a good reason).
A second possibility, is the power supply itself has a similar problem.
It detected an overload electronically (instead of by a fuse), and
in order to escape from the "latch off" state, you have to flip the switch
on the power supply to clear it.
I think there were some Antec supplies, that triggered a condition like
this with some motherboards. Using a replacement other than an Antec,
was the fix.
I don't know if there is much you can do in the way of debugging for
problems like this. For a designer, it would be relatively easy to
add a LED to a design, to indicate the design has detected a fault.
But in high volume electronics design, adding LEDs is a luxury they
cannot afford, even if it only adds $0.25 of cost for LED and driver.
computer shutting down 
Linear Mode
