failures on boot

Paul wrote:
John B. Smith wrote:

I had to look up PICO. And a Windows-running computer that small is
kinda fascinating. And for my purposes useless I think.

Our local cable company recently digitized and encrypted our signal,
bless their conniving little hearts. No way can I get my one remaining
programmable vcr to work off it. And the tv at work no longer works.
(thassa pun). However with one of those micro-baby computers I suppose
I could hook the tv up to it thru an HDMI port and enjoy a movie at
lunch? Without headphone and sub-titles I'd rather read a book.


Gawd. How awful. Everything must be hacked. Like peasants.

https://www.tivocommunity.com/commun...lecard.539683/

It's like shades of getting Netflix in Canada.

Paul

John B. Smith wrote:


Does't one other condition apply? If you switch the on/off switch on
the PSU to off, wouldn't you lose that +5VSB? The reason I don't power
down and try it myself is that switch is the main reason I'm thinking
of replacing my PSU. I think I explained in my first post that the
last time I switched the PSU off it was very cranky about getting
switched back on. So I suspected that flaky switch of causing a
momentary power drop during the boot. (though it never seems to bother
once Windows is up and running, so maybe that's not a great diagnosis)
I've been unplugging ac from the PSU if I wanted to mess around
inside. Thereby removing my ground cable to the pc at the same time.
Guess I better replace that telephone wire I used to have grounding
the chassis to the outlet plug screw that got torn off on my move. Or
butcher up another AC cable to provide a ground as you explained.

The motherboard seems to sense the difference between coming from
a "+5VSB off" state, versus a normal soft-off and soft-on with the
+5VSB flowing the whole time.

The machine I'm typing on, does a "double start" when AC power
is restored and I push the front button. And that doesn't make a lot
of sense, because it doesn't start up on its own when +5VSB is first
restored, to check the BIOS power loss policy setting. It comes
up in the soft-off state, then when I push the front button,
it does a "double start". (Fans come on for three seconds.
Fans go off for two seconds. Fans come on again and normal boot
continues. It did that from brand-new.)

The +5VSB rail only has 2 or 3 amps of output current capability,
and if the rail gets shorted, or if it's underpowered for the load,
if it winks out, the motherboard should shut off. As that voltage
runs the supervisory logic and momentary loss of +5VSB causes
the motherboard to de-assert PS-ON#.

Asus motherboards have a green LED powered directly from
+5VSB, which is used as a "safe to work" warning inside the
PC. You can't change out DIMMs or CPUs, unless the green LED
goes out. And that LED also functions as a PSU health monitor,
in the sense that if you start the PC, and you notice intensity
fluctuation in the LED, that tells you the PSU is sick or overloaded
on +5VSB. For example, some people have seen that LED flash,
which indicates the +5VSB is restarting over and over again.
If the Asus LED flashes, that means it's time for a new
PSU.

If you still see grumpy behavior, even though the +5VSB LED is
lit and not flashing or glitching, it could just be the BIOS
being a grouch.

For non-Asus motherboards, it's left to your imagination as to
what the +5VSB is doing. If you have access to "PSU extender cables"
at the computer store, you can cobble up any circuit you desire
on a PSU extender cable, without having to cut or deface your
PSU :-) If you do it that way, you won't be voiding the warranty on
the PSU or the motherboard.

When I did the "fake -5V" supply for my first PC, using a 7905
three terminal regulator, the PCB for that was fastened to a PSU
extender cable, making the solution modular and removable.

Paul

John B. Smith wrote:

If you switch the on/off switch on the PSU to off, wouldn't you lose
that +5VSB?

I didn't include mention of the PSU's own AC on-off switch because some
PSUs don't have that switch. I've found power cables to be more durable
(yank on the end, not the cable) than the typical rocker switch.
However it's done, there is +5VSB from the PSU as long as it is
connected to an A/C power source. I didn't cover an earthquake that has
a wall collapsed and cut the power cord, either.

The reason I don't power down and try it myself is that switch is the
main reason I'm thinking of replacing my PSU. I think I explained in
my first post that the last time I switched the PSU off it was very
cranky about getting switched back on. So I suspected that flaky
switch of causing a momentary power drop during the boot.

Or a dead CMOS battery. The CMOS is empty or corrupted and has to get
reloaded from the BIOS EEPROM. The CMOS table is what gets used for
settings on startup so the settings have to be in the CMOS table.

I've been unplugging ac from the PSU if I wanted to mess around
inside. Thereby removing my ground cable to the pc at the same time.

Wash hands. Have the new battery out of its packaging, cleaned, and on
hand. Remove the side panel. Disconnect from A/C power (*). Touch the
chassis first and either keep one hand on the chassis or use a grounding
strap/wire from wrist to chassis, and only touch the old battery to
slide it out and slide in the new one. Put the side panel back on,
reconnect to A/C power, and start testing for boot flakiness.

(*) Pull the power cord, flip the PSU on-off switch to Off, flip the
power strip or surge protector's power switch to Off to which the PSU's
cord is connected, or however you want to remove A/C power to the PSU.

A CMOS battery is a lot cheaper and a lot easier to replace than a PSU.