soft-power on now hard on

I have a PC with P6T "deluxe V2" mobo. Forby I turn it on at wall socket and I hear it come to life without pressing power button. Then when I shutdown from operating system, it does and screen goes blank, but the fans keep running.
I disconnected power button from mobo, methinks it were shorted, but it is still alive. I swapped power supply, and behaviour still the same. There is nothing in BIOS settings to influence this.
So, PC is still of use, but just a bit annoying. Egad, that of the zillions of transistors on that mobo, one fails for these basic functions.

wrote:
I have a PC with P6T "deluxe V2" mobo. Forby I turn it
on at wall socket and I hear it come to life without pressing
power button. Then when I shutdown from operating system,
it does and screen goes blank, but the fans keep running.
I disconnected power button from mobo, methinks it were
shorted, but it is still alive. I swapped power supply,
and behaviour still the same. There is nothing in BIOS
settings to influence this.

So, PC is still of use, but just a bit annoying. Egad,
that of the zillions of transistors on that mobo, one
fails for these basic functions.

There is actually a BIOS setting that affects power-on response.
But, this doesn't influence shutdown behavior, so having
this set incorrectly, cannot leave the fans running. So I'm not
going to repeat the irrelevant stuff that doesn't reproduce
your symptoms.

Power : APM configuration :
Restore on AC Power Loss [ Power OFF, Power ON, Last State ]

I'm guessing either power supply (control signal) failure,
something wrong with +5VSB voltage, or the driver that
drives PS_ON# from the motherboard side, is stuck driving
low. The cable could be accidentally shorted on the PS_ON#
signal, to ground. So there is a very specific section of
circuitry that can do this, and give all of your symptoms.

The front panel power supply button is "buffered". It is
a momentary contact switch, and it feeds into a logic
block. The symptoms don't directly necessarily follow
the state of the switch (crushed in the on state). It
depends on what the ATX spec says should happen if the
switch stays depressed too long. I think in the turning
on case, it may not actually turn on, until the button
is released. So the switch state could be edge sensitive
in effect, rather than level sensitive. Just because a
switch gets crushed, doesn't guarantee it stays jammed on.
If you want a computer to stay on forever, you ground
the PS_ON# signal with a shorting cable.

What is really weird about computers, is how often the
PS_ON# interface fails. It's a real puzzle as to why it
happens. On the power supply side, it doesn't use a
true logic circuit to look at the signal level on PS_ON#.
This is why, if the PS_ON# signal doesn't make a good logic
low (1.5V instead of 0.4V to 0.8V), the power supply
can be "half-on" and is then not capable of delivering
rated DC power. It won't give you your full amps
on +12V. Giving the impression the power supply has failed.
When in fact what is happening, is the motherboard logic
signal driver for PS_ON# is at fault.

So part of the debugging process, is looking at the
voltage on the PS_ON# signal. If isn't always possible,
to figure out what component drives PS_ON#, so it's pretty
difficult to compare the driving side signal, versus the
buffered copy sent across the ATX main power cable. Since a
failure in this circuit is so common, it almost deserves
a labeled monitor point on the motherboard (so you know
where to scope or use your meter).

Paul

On 4/7/15 10:25 AM, wrote:
I have a PC with P6T "deluxe V2" mobo. Forby I turn it on at wall socket and I hear it come to life without pressing power button. Then when I shutdown from operating system, it does and screen goes blank, but the fans keep running.

Try unplugging all USB devices.

If you got time, maybe you should pull the motherboard out of the
chassis for careful testing.

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BTW, google "asus p6t power problem".

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On 7/3/2015 10:25 PM, wrote:
I have a PC with P6T "deluxe V2" mobo. Forby I turn it on at wall socket and I hear it come to life without pressing power button. Then when I shutdown from operating system, it does and screen goes blank, but the fans keep running.
I disconnected power button from mobo, methinks it were shorted, but it is still alive. I swapped power supply, and behaviour still the same. There is nothing in BIOS settings to influence this.
So, PC is still of use, but just a bit annoying. Egad, that of the zillions of transistors on that mobo, one fails for these basic functions.


Check your power scheme. It's probably not turning off and simply
going to sleep or into hibernation. By "turn it on at the wall socket"
do you mean you are unplugging and plugging it in again? Have you tried
the power switch on the back of the power supply? Are you logging off?
What happens if you hold down the power switch until it shuts down? At
what point to you get that last part in your topic?

On Saturday, July 4, 2015 at 12:34:47 PM UTC+8, Mr. Man-wai Chang wrote:

Try unplugging all USB devices.

If you got time, maybe you should pull the motherboard out of the
chassis for careful testing.


I have tried unplugging stuff (disks and RAM too). I had one PC that would
do weird things if switched on with any USB device other than mouse.
I did remove the mobo to check for loose screws, but nothing extraneous,
just a lot of dust.

On Fri, 3 Jul 2015 19:25:17 -0700 (PDT), wrote:

I
have a PC with P6T "deluxe V2" mobo. Forby I turn it on at wall socket
and I hear it come to life without pressing power button. Then when I
shutdown from operating system, it does and screen goes blank, but the
fans keep running.
I disconnected power button from mobo, methinks it were shorted, but
it is still alive. I swapped power supply, and behaviour still the
same. There is nothing in BIOS settings to influence this.
So, PC is still of use, but just a bit annoying. Egad, that of the
zillions of transistors on that mobo, one fails for these basic
functions.

-
BIOS is: Computer, "come back to life" when plugging the Main House
Breaker into the wall in the garage.

Yea. If you've got good power supply units you're swapping, yea, then
you've got a messed up mainboard.

Yea. Sounds like the switch on the back to the PS is now your main
ON/OFF.

If you're not afraid, rewire the PS switch to the front of the case. I
wouldn't, but I don't usually turn off computers (BIOS is also set to
"wake computer" in the event of loss of main PWR that's restored).

By the way, one of mine, when turning the PWR off in the front, as
soon as I release it, the computer doesn't shut down but restarts
itself. Takes an inordinate time to overcome the MB logic (10 seconds
or so) for a proper shutdown. Annoying enough to either use the PS
switch or, sometimes, yank the whole damn PS plug.

Flasherly wrote:
On Fri, 3 Jul 2015 19:25:17 -0700 (PDT), wrote:

I
have a PC with P6T "deluxe V2" mobo. Forby I turn it on at wall socket
and I hear it come to life without pressing power button. Then when I
shutdown from operating system, it does and screen goes blank, but the
fans keep running.
I disconnected power button from mobo, methinks it were shorted, but
it is still alive. I swapped power supply, and behaviour still the
same. There is nothing in BIOS settings to influence this.
So, PC is still of use, but just a bit annoying. Egad, that of the
zillions of transistors on that mobo, one fails for these basic
functions.

-
BIOS is: Computer, "come back to life" when plugging the Main House
Breaker into the wall in the garage.

Yea. If you've got good power supply units you're swapping, yea, then
you've got a messed up mainboard.

Yea. Sounds like the switch on the back to the PS is now your main
ON/OFF.

If you're not afraid, rewire the PS switch to the front of the case.
Keep in mind you are talking about higher voltages here. You would want
to do this right (having a ground for instance).



I
wouldn't, but I don't usually turn off computers (BIOS is also set to
"wake computer" in the event of loss of main PWR that's restored).

By the way, one of mine, when turning the PWR off in the front, as
soon as I release it, the computer doesn't shut down but restarts
itself. Takes an inordinate time to overcome the MB logic (10 seconds
or so) for a proper shutdown. Annoying enough to either use the PS
switch or, sometimes, yank the whole damn PS plug.

On Sat, 04 Jul 2015 17:35:52 -0400, Bill
wrote:

Keep in mind you are talking about higher voltages here. You would want
to do this right (having a ground for instance).

heh - in my "jetsons," 1960 circa house...pre-groundwire days. Not
that I didn't burn out a modern pressure washer's unusually large
plug, within its accruement of electronics for serving ground
services, when cleaning the roof.

I'd probably approach it, though, to try and mimic whatever control
switch lead in the pwr supply is wired to, and duplicate that by a
similar switch, extending it to the front of the case for convenience.

Then, again, a MB going spastic about power, wouldn't take much more,
on me, for a reason to rebuild or try and swap it out for whatever's
populating it.

(Got something like that which happened last nite. A sound processing
unit's associated capacitors finally gave up the ghost and it's main
LCD display just cycles with light pulses. Being everything audio is
conveniently rendered to digital streams, and it's of course a
chip-based unit in/outputting red-laser S/PDIF, I can forgo most of
its processing/normalization modes, in a software counterpart from
computer programming applications, all except for switching back to
RCA jack phono transmission lines; A non-entity or -imposition in
practical terms for a makeship preamp, I was using it for. OTOH --
it's ton of miniscule soldering work with a package of 20 or 30
capacitors for "variously" replacing **** Engineering Behringer put
out by implementing the cheapest, crap capacitor brands, they could,
when they dropped that unit from $800US to $300, where it's sitting
prce/marketed now.)