I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

paulfoel writes:

I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

Need more info. On some like Compaq, a corrupted CMOS may result
in a totally dead PC.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

"paulfoel" wrote in message
ups.com...
I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?


Try resetting the bios...
there is usually a jumper new the battery.

Also...try the board with a minimal hardware configuration...
it's possible a component other than the mobo has failed.

If you find that the mobo is definately bad...you might as well replace
it...
repairs are rather impractical

philo wrote:

"paulfoel" wrote

I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

Try resetting the bios...
there is usually a jumper new the battery.

YES, a new battery will do no harm.

But you really need the mobo manual. Without 'resetting the CMOS' you're likely
to be wasting your time.


Graham

On 3 Sep, 10:19, "philo" wrote:
"paulfoel" wrote in message

ups.com...

I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

Try resetting the bios...
there is usually a jumper new the battery.

Also...try the board with a minimal hardware configuration...
it's possible a component other than the mobo has failed.

If you find that the mobo is definately bad...you might as well replace
it...
repairs are rather impractical

Good idea. Havent tried this....

On 3 Sep, 10:31, Eeyore
wrote:
philo wrote:
"paulfoel" wrote

I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

Try resetting the bios...
there is usually a jumper new the battery.

YES, a new battery will do no harm.

But you really need the mobo manual. Without 'resetting the CMOS' you're likely
to be wasting your time.

Graham

Still the same after resetting the CMOS...

On Sep 2, 7:05 pm, Sam Goldwasser wrote:
Need more info. On some like Compaq, a corrupted CMOS may result
in a totally dead PC.

I believe Sam meant corrupted BIOS - not CMOS. A corrupted BIOS
sometimes can still be restored - but only a few manufacturers
installed that option.

Just because power supply fans spins or LED illuminates does not
mean the power supply 'system' is working. Yes that subsystem that
can only be confirmed with a meter. Same applies to the battery.
Meter can measure that battery without removing a battery. Therefore
battery is only replaced when defective - no throwing money at
problems on speculation.

I have repaired motherboards. But it requires extensive electronics
knowledge. OP's original question implies woefully insufficient
technical knowledge. We repair things to learn. Using the meter will
provide more information - better replies here.. And if posting
numbers from that meter, then others can provide more meaningful
answers; reply with educational insights.

On Sun, 02 Sep 2007 08:22:48 -0700, paulfoel
wrote:

I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

You start by measuring the +5 volts standby power (5VSB at the ATX
power connector). Just because the LED is on does not necessarily mean
the the voltage is on spec.

If 5VSB is okay, then you measure PS_ON# while depressing the power
switch. PS_ON# should go low, turning on the power supply.

w_tom wrote:

On Sep 2, 7:05 pm, Sam Goldwasser wrote:
Need more info. On some like Compaq, a corrupted CMOS may result
in a totally dead PC.

I believe Sam meant corrupted BIOS - not CMOS. A corrupted BIOS
sometimes can still be restored - but only a few manufacturers
installed that option.

Just because power supply fans spins or LED illuminates does not
mean the power supply 'system' is working. Yes that subsystem that
can only be confirmed with a meter. Same applies to the battery.
Meter can measure that battery without removing a battery. Therefore
battery is only replaced when defective - no throwing money at
problems on speculation.

I have repaired motherboards. But it requires extensive electronics
knowledge. OP's original question implies woefully insufficient
technical knowledge. We repair things to learn. Using the meter will
provide more information - better replies here.. And if posting
numbers from that meter, then others can provide more meaningful
answers; reply with educational insights.


No, some motherboards would not boot with corrupt data stored in the
CMOS battery backed RAM in the RTC chip. Just swapping the battery
didn't fix it, the battery had to be removed and the holder shorted out
to completely discharge the FETS in the CMOS RAM.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"Michael A. Terrell" writes:

w_tom wrote:

On Sep 2, 7:05 pm, Sam Goldwasser wrote:
Need more info. On some like Compaq, a corrupted CMOS may result
in a totally dead PC.

I believe Sam meant corrupted BIOS - not CMOS. A corrupted BIOS
sometimes can still be restored - but only a few manufacturers
installed that option.

No, I do mean corrupted CMOS. A hard reset using the internal switch
(or contacts - I forget what it had) loaded defaults and restored
normal operation. It appeared totally dead before that.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

On Sep 4, 8:25 pm, Sam Goldwasser wrote:
No, I do mean corrupted CMOS. A hard reset using the internal switch
(or contacts - I forget what it had) loaded defaults and restored
normal operation. It appeared totally dead before that.

Sounds unique. BIOS will ususally perform a checksum or something
equivalent to confirm CMOS integrity. If CMOS is corrupted, then BIOS
would output an error message to the video controller. Of course, it
would not boot the OS. But the computer did boot and should display
an error message and / or associated beep code.

BIOS typically starts by performing simple concepts such as memory
checks, etc. CMOS is typically ignored until integrity of most basic
functions are first established.

Which reset are you referring? CMOS reset or computer reset?

On Sun, 02 Sep 2007 08:22:48 -0700, paulfoel
put finger to keyboard and composed:

I've got a mobo where the led comes on when the power supply is
connected but powering on does absolutely nothing. I've even tried
shorting the power button pins to rule out power button problem but
still nothing.

Is it dead? Can I do anything with it or is it new mobo time?

When you say that "powering on does absolutely nothing", do you mean
that there is no sound from the power supply, eg no kick from the fan?

If so, then looking for problems in the CMOS RAM or flash BIOS EEPROM
would be pointless. Both these devices require a functional CPU to
read them.

AFAICT, you haven't proved that your PSU is good, so the first thing
I'd do is disconnect all its loads, connect a disposable load such an
old hard drive, and then short PS_ON (pin 14, green) to any ground pin
(black).

See http://pinouts.ru/Power/atxpower_pinout.shtml

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Tue, 04 Sep 2007 20:59:10 -0700, w_tom put finger
to keyboard and composed:

On Sep 4, 8:25 pm, Sam Goldwasser wrote:
No, I do mean corrupted CMOS. A hard reset using the internal switch
(or contacts - I forget what it had) loaded defaults and restored
normal operation. It appeared totally dead before that.

Sounds unique. BIOS will ususally perform a checksum or something
equivalent to confirm CMOS integrity. If CMOS is corrupted, then BIOS
would output an error message to the video controller. Of course, it
would not boot the OS. But the computer did boot and should display
an error message and / or associated beep code.

BIOS typically starts by performing simple concepts such as memory
checks, etc. CMOS is typically ignored until integrity of most basic
functions are first established.

Which reset are you referring? CMOS reset or computer reset?

The "extended" CMOS RAM (bytes 65 and above) typically store chipset
register settings, memory timings, etc. I can see two ways in which
the CMOS RAM checksum could be valid but the register settings may not
be.

One is after a BIOS flash upgrade. Since the functions of the extended
CMOS RAM addresses are not defined by any standard, different BIOS
vendors and different BIOS versions from the same vendor may assign a
particular chipset register to a new location. If the updated BIOS
tries to use the old data, then this could have unpredictable results.

A second scenario could involve excessively aggressive memory timings
or CPU voltage/FSB settings. Overclockers would probably encounter
this from time to time.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

When you say that "powering on does absolutely nothing", do you mean
that there is no sound from the power supply, eg no kick from the fan?

If so, then looking for problems in the CMOS RAM or flash BIOS EEPROM
would be pointless. Both these devices require a functional CPU to
read them.


Correct.


AFAICT, you haven't proved that your PSU is good, so the first thing
I'd do is disconnect all its loads, connect a disposable load such an
old hard drive, and then short PS_ON (pin 14, green) to any ground pin
(black).


New PSU which passes this test.

On Sep 6, 4:53 am, paulfoel wrote:
New PSU which passes this test.

Franc's 'short the green wire' test can identify a bad power supply
but cannot identify a good one. That power supply could even boot a
system but still be defective. A defect that may cause other strange
crashes or problems months later. Again, this is where the multimeter
is so useful. First, the original power supply is confirmed good or
bad without disconnecting anything. Second, the entire power supply
'system' is verified. Third, if a new supply is installed, then that
supply is confirmed by the meter. Even a defective power supply might
boot a computer. But only a good power supply will report correct
numbers on a meter when under load and in seconds.

On Thu, 06 Sep 2007 01:53:46 -0700, paulfoel
put finger to keyboard and composed:

When you say that "powering on does absolutely nothing", do you mean
that there is no sound from the power supply, eg no kick from the fan?

If so, then looking for problems in the CMOS RAM or flash BIOS EEPROM
would be pointless. Both these devices require a functional CPU to
read them.


Correct.


AFAICT, you haven't proved that your PSU is good, so the first thing
I'd do is disconnect all its loads, connect a disposable load such an
old hard drive, and then short PS_ON (pin 14, green) to any ground pin
(black).


New PSU which passes this test.

I'd connect only the motherboard, no cards or peripherals, to the PSU.
If the PSU still won't fire up, then I'd check the motherboard for
shorts at each of the incoming rails. Otherwise you could monitor the
PS_ON pin with a multimeter while you press and release the power
button. It should switch from +5V to 0V and stay there. If PS_ON is at
0V and the PSU is not up and running, then I'd suspect that an
overload condition has shut it down.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:
On Thu, 06 Sep 2007 01:53:46 -0700, paulfoel
put finger to keyboard and composed:

When you say that "powering on does absolutely nothing", do you mean
that there is no sound from the power supply, eg no kick from the fan?

If so, then looking for problems in the CMOS RAM or flash BIOS EEPROM
would be pointless. Both these devices require a functional CPU to
read them.

Correct.


AFAICT, you haven't proved that your PSU is good, so the first thing
I'd do is disconnect all its loads, connect a disposable load such an
old hard drive, and then short PS_ON (pin 14, green) to any ground pin
(black).

New PSU which passes this test.

I'd connect only the motherboard, no cards or peripherals, to the PSU.
If the PSU still won't fire up, then I'd check the motherboard for
shorts at each of the incoming rails. Otherwise you could monitor the
PS_ON pin with a multimeter while you press and release the power
button. It should switch from +5V to 0V and stay there. If PS_ON is at
0V and the PSU is not up and running, then I'd suspect that an
overload condition has shut it down.

- Franc Zabkar
Also, no memory...or a known good, single stick....

jak