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I demoted my older desktop computer to a server a short while back and it has always had some sort of problem with powering on after a complete power loss.

For instance, right now it's powered on and running fine. If I power it off, I can easily power it back on without any problems.

However, if I power it off, and then disconnect the power chord, then reconnect and attempt to power it on, anything short of a prayer and a miracle will not make it power on, and I have to keep trying for what seems like ages to get it to power on.

One thing that seems to increase its chance to power on is to disconnect everything except the power chord. USB cables (even for mouse and keyboard), monitor cable, network cable, etc. everything has to go.

Also, the longer I just let the machine sit there, connected to power, but powered off, with nothing else connected, seems to increase the chance of it powering on.

What likely items in the machine can be the problem? I'm assuming it's a problem with the power unit, that it can't manage to deliver enough juice to the rest of the system when everything is connected and probably drawing minute quantities of power from it, but what about the fact that it seems to be easier to power it on the morning after I reconnect the power to it than the same evening? Is there something in there that needs to recharge?

This machine is usually left on 24/7 for home server purposes so it hasn't niggled me all that much, but a couple of nights ago there was a big thunderstorm in the area so I disconnected everything, and I had to reconnect it one day and power it on the next day to get it back in order.

Has anyone else seen this kind of behaviour? I'm loath to begin replacing elements in it since the problem doesn't come up all that often, and I'd hate to start replacing the power unit only to find out that this is a typical problem with the thingamajig connected to whatsitsname on the motherboard.

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"disconnect the power chord" - rock and roll to the rescue! –  Josh Comley Nov 19 '09 at 14:12
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7 Answers 7

up vote 7 down vote accepted

Your power supply is more than likely the culprit here, it is probably not letting go of the power that is stored in the capacitors.I do not know the exact science behind why this works, but I do know that if you clear the power it will work. To do this you will need to power off the machine, then unplug it, then press the power button a few times to clear the stored power, plug it back in, and then try to power it on. That should solve the problem.

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I will try that the next time this crops up, I'll let the machine be for the time being, thought I'd just post here to see if someone had a "Ah, you need to wiggle that ..." sort of solution, and I'll definitely try what you said. Thanks. –  Lasse V. Karlsen Jul 17 '09 at 14:26
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If this does not work, you could have a leaky capacitor on the Motherboard. I have also experienced this. The problem would be intermittent as well. –  Molex Jul 17 '09 at 14:30
    
I think this is more common for cheaper Power Supplies. –  Brad Gilbert Jul 17 '09 at 21:34
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I suspect that the culprit here is either going to be the power supply or the motherboard.

If you have other PCs in the house, I would try borrowing a power supply from one of them and hooking it up to the problem PC. You don't even have to fully install it in the machine, just get it close enough so the wires can be plugged in.

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Unfortunately I don't have any machines with a compatible power supply handy. I'll see if I can scrounge one from an old machine at work though. –  Lasse V. Karlsen Jul 17 '09 at 15:06
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It's the power supply. If it's loaded too heavily on startup, and if the capacitors are bad, then it won't easily start up - it'll start, but then think there's a problem because it can't keep itself in regulation, so it'll shut down.

Replace the power supply. If you open up the old one you're very likely to find bulging or leaking capacitors.

-Adam

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I would think that this is a power unit beginning to go bad.

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As you and everyone has mentioned, I would get that power supply swapped out. You said it runs 24/7 and it is older. That is probaly one of the most common parts that needed to be replaced on older systems still in use. Try and dig up a used one out of an older computer.

If you buy a new one, you might want to consider one that is rated at least a 80+ power efficiency rating since you are running a 24/7 computer.

I usually find older power supplies that have died full of dust and sometimes other random office supplies in them. haha. Computers that are not kept clean die faster.

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While I completely agree with everyone who suggests dodgy power supply as the most likely culprit, a possible alternative, with a much cheaper fix, is flat CMOS battery - occasionally this can cause random weirdness on startup. Worth checking before going for more expensive fixes...

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What everyone else said, but I also found that IBM 6221/6223 servers had this quirk- when HyperThreading was enabled in the BIOS. Turn hyperthreading off, and we no longer had to pull the power cord in order to get it to reboot unattended.

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