HP Pavilion 7800 CTO

Hi,

I am trying to debug an apparent power supply/motherboard problem
on my sister-in-law's HP Pavilion 7800 CTO machine. Orginally, she
was having problems where the machine would not power on when she
hit the switch. I looked inside and without really doing anything it
started to work again for about a month. Then it has the same problem
so I tried replacing the power supply. That worked for a short period
of time (a couple of days) but then it just died hard and now there is
nothing that can be done to boot it.

The current situation is that when I hit the switch, the fan on the power
supply does a very quick whirl and nothing happens. Subsequent pulses
of the fan do nothing either. I took a volt-meter and looked at the
20 pin power connector on the board while playing with the switch. At
the start, the 5VSB signal is 5V so I know that there is power to the
switch. I also see that the P_ON signal is high, which I understand is
pulled up by a resistor in the supply. When I hit the switch, I see that
the P_ON signal pulls low and stays low as should be. The P_OK
signal is not okay, though, just 0V. It looks like the supply does not
like something on the board - maybe a short? What other things would
be worth looking at here? Or does it just mean a bad motherboard that
I should replace? Sounds from another thread like that could end up
an O/S headache.

Thanks,
Tim

"TPM" <> a écrit dans le message de news:
aKCdnYgqrur-...
> Hi,
>
> I am trying to debug an apparent power supply/motherboard problem
> on my sister-in-law's HP Pavilion 7800 CTO machine. Orginally, she
> was having problems where the machine would not power on when she
> hit the switch. I looked inside and without really doing anything
> it
> started to work again for about a month. Then it has the same
> problem
> so I tried replacing the power supply. That worked for a short
> period
> of time (a couple of days) but then it just died hard and now there
> is
> nothing that can be done to boot it.
>
> The current situation is that when I hit the switch, the fan on the
> power
> supply does a very quick whirl and nothing happens. Subsequent
> pulses
> of the fan do nothing either. I took a volt-meter and looked at the
> 20 pin power connector on the board while playing with the switch.
> At
> the start, the 5VSB signal is 5V so I know that there is power to
> the
> switch. I also see that the P_ON signal is high, which I understand
> is
> pulled up by a resistor in the supply. When I hit the switch, I see
> that
> the P_ON signal pulls low and stays low as should be. The P_OK
> signal is not okay, though, just 0V. It looks like the supply does
> not
> like something on the board - maybe a short? What other things
> would
> be worth looking at here? Or does it just mean a bad motherboard
> that
> I should replace? Sounds from another thread like that could end up
> an O/S headache.
>
> Thanks,
> Tim
>

Tried removing and putting back every parts on the motherboard. For
example, on my desktop computer, once, it didn't want to boot up, I
removed and replace the memory and it worked back.

Deko

"Deko" <> wrote in message
news:FRflf.7375$...
> "TPM" <> a écrit dans le message de news:
> aKCdnYgqrur-...
>> Hi,
>>
>> I am trying to debug an apparent power supply/motherboard problem
>> on my sister-in-law's HP Pavilion 7800 CTO machine. Orginally, she
>> was having problems where the machine would not power on when she
>> hit the switch. I looked inside and without really doing anything it
>> started to work again for about a month. Then it has the same problem
>> so I tried replacing the power supply. That worked for a short period
>> of time (a couple of days) but then it just died hard and now there is
>> nothing that can be done to boot it.
>>
>> The current situation is that when I hit the switch, the fan on the power
>> supply does a very quick whirl and nothing happens. Subsequent pulses
>> of the fan do nothing either. I took a volt-meter and looked at the
>> 20 pin power connector on the board while playing with the switch. At
>> the start, the 5VSB signal is 5V so I know that there is power to the
>> switch. I also see that the P_ON signal is high, which I understand is
>> pulled up by a resistor in the supply. When I hit the switch, I see that
>> the P_ON signal pulls low and stays low as should be. The P_OK
>> signal is not okay, though, just 0V. It looks like the supply does not
>> like something on the board - maybe a short? What other things would
>> be worth looking at here? Or does it just mean a bad motherboard that
>> I should replace? Sounds from another thread like that could end up
>> an O/S headache.
>>
>> Thanks,
>> Tim
>>
>
> Tried removing and putting back every parts on the motherboard. For
> example, on my desktop computer, once, it didn't want to boot up, I
> removed and replace the memory and it worked back.
>
> Deko
>

Thanks for the advice. I have actually tried that and it does not seem to
have helped but I will play with it a bit more.

Tim