Previously Emerald Saint <xp.student RemoveThis @comcast.net> wrote:
> When I turn power off the power goes OFF then ON then OFF then ON for about
> ten seconds before it stay completely off. The OFF/ON periods are about 1
> or 2 seconds. This problem happens for 'soft' OFF or 'hard' OFF. Also the
> problem can go away for many days of using the computer but it has recently
> returned and is happening very often now. I thought of a few ways to 'fix'
> the problem with a kludge, but I haven't tried anything yet because I would
> like to hear what people here have to say. I haven't done any meter
> measurements yet. Has anyone here ever seen a PC behave like that?
This sounds like a malfunction in either the PSU or the mainboard
power control circuit. It may, for example, be a bad 5Vsb (standby)
line that cause the control circuit on the mainboard to loose its
state and switch on again.
TAs this behaviour is very stressfull for the hardware, you should
fix it ASAP. One way to find the problem is to try with a different
PSU.
> I could cut the green wire in the power supply (PSU) wiring harness and
> connect it to one of the ground wires. That would tell the PSU to always
> stay turned on. Then I could use the toggle switch on the rear of the PSU
> to turn the PSU on or off. Maybe that defeats a safety feature that
> protects the MOBO or PSU when a short circuit happens. I don't know.
In principle this would work. Problem is that the switches on
the rear are not intended for frequent use and could die quickly.
The second problem is that indeed the PSU may not be designed
for this and may die or malfunction after some time. A well-designed
PSU should work with this though.
> Another question. The normal way to turn power on is to momentarily
> close circuit on the two wires on the front power button.
Correct.
> The MOBO
> tells the PSU to turn on (via the green wire) when it senses the
> closed circuit on the two pins. Possibly there is a window here
> where the MOBO determines if conditions are safe for applying power
> before it applies ground on the green wire.
No. The mainboard only determines whether it should switch on or
off. No additional checks, at leas none are required AFAIK.
> My kludge would amount
> to defeating that safety feature. Possibly all unsafe conditions
> are handled by the POWER GOOD signal totally independent of the
> kludge I'm talking about - in which case I don't need to worry. I
> don't know.
The power safetu featires (current/temperature//voltage) are, if
present, all done by the PSU itself. The mainboard is not involved
and the power-on signal is not intended to be used by any critical
safety feature.
> I would guess my problem is a MOBO problem not a power supply
> problem. But like I say, I haven't done any meter testing or wiring
> kludges yet.
Can be both, see above.
> I haven't seen this problem occur when I shut down by
> simply turning the PSU off with the switch on the back. Maybe it
> does happen but I have never seen it yet.
No, it cannot. The switch on the back is the equivalent of
pulling the plug: It disconnects the mains voltage physically.
Arno
>> Stay informed about: Power ON/OFF malfunction on P4P800-SE 
FAQ
Search
Profile
Private Messages
Log in/Register/Password
