Odd Power On Problem

[Jason]

This one has stumped myself and quite a few others including the
internal support team at my work place:

Shut down Windows turns off the machine (as it should).
Power button then does nothing! (Power is definately being supplied to
the board as standby light is on but fan doesn't spin, etc.).

Fix:
Either disconnecte absolutely every peripheral and then try and power
it on again

OR

Turn off the PSU, hold down the power button for 10 seconds then try
to power it on again.

I cannot for the life of me understand why this should be. The problem
started extremeely renadomly a few months back for no logical reason
i.e. no changes to hardware configuration or updates to the BIOS.
Motherboard is an ASUS Mini-ATX Socket A, A7S8X-MX (model number is
from memory so could be wrong) and their support department were
equally as stumped.

Has anyone come across this before? I'd almost say it's a BIOS setting
but I can't see anything regarding it o_O

Semi short term solution is of course, never power the thing off but I
intend to do some internal cleaning soon and I'm pretty sure
subjecting a heat sink to rapid cooling with a compressed air can
isn't the best idea in the world.

 

[JAD]

PSU problem

 

[Mike T.]

This one has stumped myself and quite a few others including the
internal support team at my work place:

Shut down Windows turns off the machine (as it should).
Power button then does nothing! (Power is definately being supplied to
the board as standby light is on but fan doesn't spin, etc.).

Fix:
Either disconnecte absolutely every peripheral and then try and power
it on again

OR

Turn off the PSU, hold down the power button for 10 seconds then try
to power it on again.

I cannot for the life of me understand why this should be. The problem
started extremeely renadomly a few months back for no logical reason
i.e. no changes to hardware configuration or updates to the BIOS.
Motherboard is an ASUS Mini-ATX Socket A, A7S8X-MX (model number is
from memory so could be wrong) and their support department were
equally as stumped.

Has anyone come across this before? I'd almost say it's a BIOS setting
but I can't see anything regarding it o_O

Semi short term solution is of course, never power the thing off but I
intend to do some internal cleaning soon and I'm pretty sure
subjecting a heat sink to rapid cooling with a compressed air can
isn't the best idea in the world.

You could try resetting CMOS by shorting the clear_cmos jumper. But I
suspect you have a power supply that is failing.

When you hit the power button on the front of the case, many things happen
before windows starts loading. ONE of those steps is, the power supply has
to send a Power_OK signal to the CPU through the mainboard. Before this
happens, the motherboard might appear to be on but not doing anything, as
the CPU is still waiting for power_ok.

Disconnecting all peripherals? Less load on power supply, DC voltages in
power supply ramp up faster, power_ok is sent to CPU before mainboard times
out (it won't wait forever).

Hold down power button for ten seconds and then try to power up again?
Here, you are delaying system startup a while, giving power supply time to
ramp up voltages so that CPU receives power_OK when it is expecting to.

At least that's my theory. I'd be surprised if replacing the power supply
with a good name-brand unit like fortron or seasonic or enermax would not
fix this problem. But clearing CMOS won't cost anything, and won't hurt
anything, so try that first. -Dave

 

[Jason]

Thanks for the suggestions from both of you. I'd..be surprised if it
was the PSU as it's a) relatively new and b) pretty beefy but I'll see
if I can get one on the weekend and give it a try.
As an aside, what Wattage have you got yourselves?

 

[JAD]

S12 600 Seasonic in my new rig. these next few you can't go wrong with. All
premium PSU's at a premium price (unfortunately)

Enermax Whisper II EG565P-VE
Antec TCII-550
SilverStone Zeus ST65ZF
Hiper Type-R Modular HPU-4B580 (this one is really different)
Enermax Coolergiant VH 600W

 

[Jason]

Thanks, as for prices, well if it needs to be done, it needs to be
done. Thank god I have a full time job.

 

[Mike T.]

Thanks for the suggestions from both of you. I'd..be surprised if it
was the PSU as it's a) relatively new and b) pretty beefy but I'll see
if I can get one on the weekend and give it a try.
As an aside, what Wattage have you got yourselves?

That shouldn't matter, as we aren't running your hardware. But last
couple of systems I built were a Seasonic 380 and an Enhance 460. If your
system is socket A, anything around ~400W or better should be more than
enough. ASSUMING a good brand. -Dave

 

[Rod Speed]

This one has stumped myself and quite a few others
including the internal support team at my work place:

Shut down Windows turns off the machine (as it should).
Power button then does nothing! (Power is definately being supplied to
the board as standby light is on but fan doesn't spin, etc.).

Fix:
Either disconnecte absolutely every peripheral
and then try and power it on again

Turn off the PSU, hold down the power button
for 10 seconds then try to power it on again.

I cannot for the life of me understand why this should be.

You've got a fault. Much more likely to be the power supply than the motherboard.

The problem started extremeely renadomly a few months back for no logical
reason i.e. no changes to hardware configuration or updates to the BIOS.

Thats what happens when a fault shows up.

Motherboard is an ASUS Mini-ATX Socket A, A7S8X-MX
(model number is from memory so could be wrong) and
their support department were equally as stumped.

Doesnt say much for their capabilitys.

Has anyone come across this before?

Yep, it isnt that uncommon a fault.

I'd almost say it's a BIOS setting

Nope, just a fault.

but I can't see anything regarding it o_O

Yeah, there's no setting that will produce that effect.

Semi short term solution is of course, never power the thing
off but I intend to do some internal cleaning soon and I'm
pretty sure subjecting a heat sink to rapid cooling with a
compressed air can isn't the best idea in the world.

Just leave it off and let it cool down before cleaning.

You should be able to work out whether the problem is with
the power supply or the motherboard by using a multimeter
and checking the POWER_GOOD and PS_ON# lines, grey
and green, but of you cant do that, its much more likely to
be the power supply than the motherboard. The fact that its
relatively new doesnt prove anything, those can have faults too.

 

[w_tom]

Thanks, as for prices, well if it needs to be done, it needs to be
done. Thank god I have a full time job.

No reason exists to suspect a power supply failure. Power supply
'system' is more than a power supply. This problem is more
symptomatic of the power supply controller. One does not just say "it
sounds like....". One does not do such wild speculation. First gets
facts - 'follow the evidence'.

A tool so ubiquitous as to be sold even in K-mart is a $20 3.5 digit
multimeter. In but a minute, a suspect is identified. Simply monitor
voltage on the green wire (from power supply to motherboard). When
powered off, this wire will measure more than 2 volts. When powered
on, this wire will measure less than 0.8 volts. Power supply should
always react as green wire commands.

If power supply does as controller orders (via green wire), then
inputs to controller are examined. Measure voltage on purple wire - a
special power supply only for that power supply controller. Voltage
must remain above 4.87 volts DC when computer is powered on or off.
If too low, then reason for failure has been identified. If OK, then
power supply is not defective; speculation was wrong.

Voltage on two power switch wires are measured where wires connect
to motherboard. Must be more than 2.4 volts when not pressed and near
zero volts when switch is pressed. If these inputs are correct, then
suspect the power supply controller hardware. An inspection of
electrolytic capacitors (that part of motherboard) might reveal reason
for the slow and getting worse failure.

'Follow the evidence' is why a digital meter is as important as a
screwdriver; why solving a problem occurs only after first identifying
the suspect. In this case, three possible suspects are verified or
accused.

 

[Rod Speed]

No reason exists to suspect a power supply failure.

MIndless pig ignorant silly stuff. Of course there is when
the system wont power on again after its been shut down
without unplugging the power supply from the wall etc.

<reams of your pig ignorant mindless shit flushed where it belongs>