ep45-ds3l : No Power?

Last nite my EP45-DS3L suddenly would not boot - no power light,
no mobo led, nothing.

This followed a few losses of power due to a flaky surge
protector under the desk.

First thing that occurred to me was that the power supply had
bitten the big one.

But I swapped it out for a known good power supply and the
symptoms were the same: no sign of power.

That seems to suggest it's not the power supply.

Then I took an old power supply, plugged it in, and tried turning
it on - with no connections to a mobo. Fan sort of twitched,
and then nothing.

This led me to believe that the power supply somehow senses
something on the mobo that tells it whether it's safe to go or
not.

Am I on the right track?

If so, could there be something on the mobo like a fuse or a
circuit breaker that's blown/tripped?

Or is the mobo toast?

--
PeteCresswell

On Sat, 22 Aug 2009 09:22:33 -0400, "(PeteCresswell)" <x@y.Invalid>
wrote:

>Last nite my EP45-DS3L suddenly would not boot - no power light,
>no mobo led, nothing.
>
>This followed a few losses of power due to a flaky surge
>protector under the desk.
>
>First thing that occurred to me was that the power supply had
>bitten the big one.
>
>But I swapped it out for a known good power supply and the
>symptoms were the same: no sign of power.
>
>That seems to suggest it's not the power supply.
>
>Then I took an old power supply, plugged it in, and tried turning
>it on - with no connections to a mobo. Fan sort of twitched,
>and then nothing.

When you turn on the power supply using the switch that's on the power
supply, the only power that turns on is the standby power (5Vsb on the
ATX power connector).

>
>This led me to believe that the power supply somehow senses
>something on the mobo that tells it whether it's safe to go or
>not.

5Vsb powers control circuitry on the motherboard that allows the
motherboard to turn on the power supply (PS_ON on the ATX power
connector) when the power button on the front of the PC case is
depressed.

>
>Am I on the right track?

The sequence of events is:
1. Turning on power supply switch causes 5Vsb to go to +5 volts.
2. Pressing power button on case causes PS_ON to go from > +2.4 volts
down to < +0.8 volts, turning on full power to the motherboard and
drives.

>
>If so, could there be something on the mobo like a fuse or a
>circuit breaker that's blown/tripped?
>
>Or is the mobo toast?

Per andy:
>>Am I on the right track?
>
>The sequence of events is:
>1. Turning on power supply switch causes 5Vsb to go to +5 volts.
>2. Pressing power button on case causes PS_ON to go from > +2.4 volts
>down to < +0.8 volts, turning on full power to the motherboard and
>drives.

I *think* I'm at the bottom of it all now.

Seems like if there's a fault somewhere in the drives or other
devices it can prevent the mobo from telling the power supply to
turn on power to the mobo.

I didn't have the expertise to check for the +5 volts, but I got
it down to where if my data drive was connected the power supply
would not turn on when I pressed the case's Start button.

Disconnected the drive, mobo fired right up.

Took the problem drive to work, hooked it into my HP PC there...
HP booted up, but took a looooong time.... and the drive was not
visible, albeit spinning.
--
PeteCresswell