Re: Computer wont power up sometimes, runs fine

dzmcm@xxxxxxxxxxx wrote:

Not to me it doesn't. I'd be shocked if replacing your power supply
doesn't solve this problem. The system draws most current at
start-up. When cold, the power supply is least able to supply this
extra current. After warmed up for a while, the power supply might
be able to just supply enough current to keep the system running.
So startup problems are a classic (bad power supply) symptom.

Which is why I contacted OCZ support first. However, i'm not running
a monster rig. My videocard requires no additional power source. And
I have tested with minimal components. This is a 500w powersuply
and a great quality. It isn't some lightweight overated piece of crap
that manufacturers include with cheap cases.

Sure, but that doesnt exclude the possibility of a fault rather
than lack of capacity. A fault that gets it wrong at startup time,
decides that there is too much load on the supply when there isnt.

And it runs fine for days under heavy load
with no stability problems whatsoever.

Sure, but all that means is that the fault is in the overcurrent detection.

I'm not dismissing the possibility that it could be the powersupply.
It's just unlikly.

It is however even less likely that a motherboard
would produce those particular symptoms, particularly
taking days to boot again when it wont boot.

You sure its days and not just an hour or so unplugged ?

My theory is that there is a sensor that has gone bad (maybe a temp
sensor on the mobo) that is causing it to shut down for safety reasons.

That wouldnt produce that set of symptoms, only being a problem
at boot time, and taking days to boot again once it wont boot.

It may even be my cpu fan sensor.

Very unlikely given that it should be at the lowest temp at boot time.

I realy don't know though.

Yep, you clearly dont understand fault finding very well.

I've tried to find more information concerning the interaction
between the powersupply and motherboard with little success.

Yeah, it isnt very clearly spelt out, you really need to understand
how the power supply over current protection works.

I've also tried to find more in depth info on anything and everything
inside a powersupply. If anyone knows some good links I'd greatly
apreciate it. Afterall there are few pleasures greater than learning.

I'm not aware of any good source on that.

In any case, I do know that all my fans DO spin.
Including the chipset fan hidden behind the videocard.

All that means is that the power supply does come up initially and then
shuts down. Most likely because its decided that the load on power
supply is too high, and it does that due to a fault in the power supply.

I know that cpu fan failure will shutdown my system according
to my bios settings (assuming I have said setting enabled).

Yes, but the cpu temp should be at it lowest when it shuts down.

And wont take days to cool off either.

But there is no failure.

I'd like to test with a spare power supply,

Yeah, thats the only really viable test.

but I don't have any 20+4 pin spares (only 20 pin).

One approach is to buy another which you can return if it
doesnt fix the problem. Not ideal tho if its still under warranty.

If you bought it complete, didnt assemble it yourself,
you could just get the supplier to try a different power
supply, if its still under warranty.

And, like I said, I can get the powersupply running,
just not when it's triggered by the motherboard.

That doesnt eliminate the obvious possibility of
a fault in the over current detection circuitry.

I've even tested the power switch on the case.

A faulty power switch wouldnt see it power up for a very short time.

I would gladly purchase a new motherboard or powersupply (I don't mind
having spares). But my employment status just doesn't permit me to.

Guess you could just leave it on all the time when it does boot.

Could be a complete pain in the arse if you get many power glitches tho.


The short story is that its very unlikely for a faulty
motherboard to produce those particular symptoms.

Even bad caps are unlikely to with the motherboard.


.

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