PC power-on troubles

T

Tom Del Rosso

Guest
The PSU and mobo are a couple of years old, but previously tested good.
They've been in storage, and I just put them in a new case.

5v standby is good. Power switch works and is in the right place. But when
I close the power switch, the power-on pin (of the ATX power connector)
stays high (4.4v).

The 5v standby line is 5v disconnected and 4.4v plugged in. That sounds
like too much of a load.

Hey! The fans just spun for an instant when I wasn't even touching it.

Now the fans spin for a second when I press power.

Maybe something is loose or shorted.

Will try without the video card and other connectors (like reset)
disconnected.


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"Tom Del Rosso" <td_03@verizon.net.invalid> wrote in message
news:jbb23h$lqr$1@dont-email.me...
The PSU and mobo are a couple of years old, but previously tested good.
They've been in storage, and I just put them in a new case.

5v standby is good. Power switch works and is in the right place. But
when I close the power switch, the power-on pin (of the ATX power
connector) stays high (4.4v).

The 5v standby line is 5v disconnected and 4.4v plugged in. That sounds
like too much of a load.

Hey! The fans just spun for an instant when I wasn't even touching it.

Now the fans spin for a second when I press power.

Maybe something is loose or shorted.

Will try without the video card and other connectors (like reset)
disconnected.
Click to expand...

By the sound of that, I'd download the user manual and re-check all the
front panel connectors.
 
Ian Field wrote:
"Tom Del Rosso" <td_03@verizon.net.invalid> wrote in message
news:jbb23h$lqr$1@dont-email.me...
The PSU and mobo are a couple of years old, but previously tested good.
They've been in storage, and I just put them in a new case.

5v standby is good. Power switch works and is in the right place. But
when I close the power switch, the power-on pin (of the ATX power
connector) stays high (4.4v).

The 5v standby line is 5v disconnected and 4.4v plugged in. That sounds
like too much of a load.

Hey! The fans just spun for an instant when I wasn't even touching it.

Now the fans spin for a second when I press power.

Maybe something is loose or shorted.

Will try without the video card and other connectors (like reset)
disconnected.


By the sound of that, I'd download the user manual and re-check all the
front panel connectors.


good idea. Check the voltage on the switch pin when you press the switch.
Click to expand...

The switch typically goes through a huge "glue chip" before reaching
the power on pin on the psu.

If you figger it out, post the result. I've got a mobo with the same
problem. The switch wire goes under a smt chip and can't be probed further.
In my case, forcing the psu to turn on doesn't help.
 
Tom Del Rosso wrote:
The PSU and mobo are a couple of years old, but previously tested good.
They've been in storage, and I just put them in a new case.

5v standby is good. Power switch works and is in the right place. But when
I close the power switch, the power-on pin (of the ATX power connector)
stays high (4.4v).

The 5v standby line is 5v disconnected and 4.4v plugged in. That sounds
like too much of a load.

Hey! The fans just spun for an instant when I wasn't even touching it.

Now the fans spin for a second when I press power.
Click to expand...
My experience under the conditions you describe would indicate the
power supply is failing. It could also be the MB, but the failing item
is most often capacitors that have lost some of the capacitance. If you
have a ESR meter, check the caps. My guess is you will find some bad
ones that are preventing the power from coming up fast enough.

Maybe something is loose or shorted.

Will try without the video card and other connectors (like reset)
disconnected.
Click to expand...
 
Ken wrote:
Tom Del Rosso wrote:
The PSU and mobo are a couple of years old, but previously tested good.
They've been in storage, and I just put them in a new case.

5v standby is good. Power switch works and is in the right place. But
when
I close the power switch, the power-on pin (of the ATX power connector)
stays high (4.4v).

The 5v standby line is 5v disconnected and 4.4v plugged in. That sounds
like too much of a load.

Hey! The fans just spun for an instant when I wasn't even touching it.

Now the fans spin for a second when I press power.

My experience under the conditions you describe would indicate the power
supply is failing. It could also be the MB, but the failing item is most
often capacitors that have lost some of the capacitance. If you have a
ESR meter, check the caps. My guess is you will find some bad ones that
are preventing the power from coming up fast enough.


Maybe something is loose or shorted.

Will try without the video card and other connectors (like reset)
disconnected.
Click to expand...
Also connect your POST board and look up
the codes (for YOUR BIOS) that the MB tosses at you.
http://www.computerhope.com/beep.htm
http://www.computerhope.com/issues/ch000607.htm

--Winston
 
On Fri, 2 Dec 2011 12:32:07 -0500, "Tom Del Rosso"
<td_03@verizon.net.invalid> put finger to keyboard and composed:

Now the fans spin for a second when I press power.

Maybe something is loose or shorted.
Click to expand...
Sounds like a short on one of the outputs. Should be easy enough to
locate with a multimeter.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
"Ian Field" <gangprobing.alien@ntlworld.com> wrote in
news:Gg8Cq.64832$3Y.58290@newsfe18.ams2:

"Tom Del Rosso" <td_03@verizon.net.invalid> wrote in message
news:jbb23h$lqr$1@dont-email.me...

The PSU and mobo are a couple of years old, but previously tested good.
They've been in storage, and I just put them in a new case.

5v standby is good. Power switch works and is in the right place. But
when I close the power switch, the power-on pin (of the ATX power
connector) stays high (4.4v).

The 5v standby line is 5v disconnected and 4.4v plugged in. That sounds
like too much of a load.

Hey! The fans just spun for an instant when I wasn't even touching it.

Now the fans spin for a second when I press power.

Maybe something is loose or shorted.

Will try without the video card and other connectors (like reset)
disconnected.


By the sound of that, I'd download the user manual and re-check all the
front panel connectors.
Click to expand...
I had a PC that would beep and not start up;replacing the CPU fan fixed it.
the old CPU fan still ran,but apparently drew too much current. I only
noticed it when I left the fan disconnected while checking other things,and
the PC started right up. a new fan from Skycraft,and no more problem.

--
Jim Yanik
jyanik
at
localnet
dot com
 
Skycraft in Florida ? Or are there more ?

Go figure, I go to Florida and think of Skycraft as a hot tourist
spot !

Anyway what I would like to know is if the fan will run if the
processor is bad. I got two dead boards here, on one the fans run and
on the other they don't. On the one on which they don't the PS has
been tested by substitution and continuity to the power switch has
been confirmed.

J
 
mike wrote:
If you figger it out, post the result. I've got a mobo with the same
problem. The switch wire goes under a smt chip and can't be probed
further. In my case, forcing the psu to turn on doesn't help.
Click to expand...
In this case, it's the caps in the PSU.


--

Reply in group, but if emailing add one more
zero, and remove the last word.
 
On Dec 2, 9:35 pm, Jim Yanik <jya...@abuse.gov> wrote:

I had a PC that would beep and not start up;replacing the CPU fan fixed it.
the old CPU fan still ran,but apparently drew too much current. I only
noticed it when I left the fan disconnected while checking other things,and
the PC started right up. a new fan from Skycraft,and no more problem.

--
Jim Yanik
jyanik
at
localnet
dot com
Click to expand...
I'm intrigued...seriously! Thanks, I may have had one like that and
never thought of the possibility!
 
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