Weird startup-then immediate power-down behavior

Hey folks,

Essentially that is what started happening with my older system yesterday morning, much to my surprise. Not even enough time for the system to POST, I don’t think (at most about 3 seconds between hitting the power switch and having the system just mysteriously power down).

Anyway, when I pulled the power cord out of the back of the power supply, waited about 10 or 15 seconds, and put it back in, it started up fine. Same behavior this morning, same solution.

Anyone have an idea of why this might be happening?


Older rig: Athlon XP 2500+, 1GB PC2700 RAM, 128MB GeForce 6600GT, ASUS A7N8X Deluxe, Audigy 1 soundcard.

It sounds like the CPU is overheating and the system is shutting down to avoid damage.

Id guess one of two things is happening.

  1. The cooling unit for the CPU is dying. Maybe the fan is gummed up and doesn’t spin up some times.

  2. The thermal sensor for the CPU is going bad and giving false readings.

After one of these incidents, open your case and touch the heat-sink on the CPU. At worst, it should just be very warm. If it is really hot, like you can’t keep your finger on it for more then a few seconds, then it is not cooling properly.

It also would not hurt to dust out your case, maybe the cooling vents on the heat sink are just full of dust.

If your heatsink is cool, then the problem lies elsewhere.

It’s either what DeepT said, or your power supply is busted.

Yeah, what they said.
Your mobo has to receive a clean signal from your power supply in order to boot up completely.
I sometimes have a similar problem, probably because my power supply is a cheap generic.
Apart from the CPU heatsink, you can try blowing out the power supply also, since it tends to accumulate dust, and eventually it’ll overheat.

I have a crappy ASUS AMD motherboard which requires me to start with partially drained capacitors.

The best solution I have found is taking the hard power switch in back and flicking it on and off while hitting the power button on the front. If you catch it at just the right charge it will POST. Otherwise it just sits there with all of the lights on.

Have you gotten into an argument with chet lately?

Thanks for the replies.

I went ahead and used canned air to blow dust out of the CPU heatsink and fan, the main case fan, and the power supply. The CPU fan seems to be working still, so I suppose it may be the thermal paste business. Still, if it were in fact a question of the CPU overheating too quickly, why would doing a “true” power-down of the system (including the power supply by pulling its cord out) make the behavior different? It’s almost as if, when the PS or the mobo has some standby power, it “remembers” something that it forgets if it’s truly powered down.

I started it and hit Delete immediately to get to the BIOS so I could monitor its reported CPU temp. After just about 3 or 4 minutes it had climbed to 45 C. Does that sound like it’s too hot? I am in an upstairs room, but it’s been really cool today and it might be all of 75 Fahrenheit in here tops. I put a finger on the CPU heatsink and it just feels a little warm, not blisteringly hot at all–maybe it’s not pulling enough heat away from the CPU?

One thing, while the Q-Fan option in the BIOS was enabled, it didn’t appear to be connected right (at least as far as the BIOS was concerned). I wonder if that might be the problem. The reported CPU fan speed BTW was about 3150 RPM or so.

You could also have a short in your system, and the power supply is powering down when it detects the fault.

Wouldn’t that prevent the system from powering up and functioning at all? Because once I get it going, it seems to work fine (at least for web browsing and email, and downloading podcasts via iTunes).

If it keeps powering down randomly like that and your heatsink isn’t too hot (Or you have been watching the temp) then I would suggest it is the power-supply.

Id also try and re-seat all the connectors / cards to make sure they didn’t get loose. If you moved your computer it is possible a connector pulled a little loose and may be making intermittent contact.

You’re right. I misread your post and did not realize you had power for a whole 3 seconds before shutdown. Sorry for my misunderstanding.

Power supply would be my first guess.

Thanks for the replies. After shooting canned air into the thing the other day I also plugged it into a different surge protector, and since all that the original problem hasn’t reoccurred. Still, the rather high reported CPU temps (48 to 50 C with just browsing/email and such, no gaming) have me concerned, so I bought a new HSF and will see whether replacing the current one helps.

Bumpage to let everyone know that the problem came back, which is why I asked in another thread about another Antec PSU.

Wait, so your PSU and your hard disk are dying? How about simply getting a new system?

I’ve already got a newer rig–I just like having two is all. :-) Besides, my whole iTunes library is on this older one. Plus, this was the one I built myself from the ground up, so there’s a sentimental attachment.

But yeah, I am seriously considering moving my iTunes stuff to the new machine.