Unexpected power off

[paul.brett]

Hello all,

My wife's Compaq Presario was the subject of a power cut (and possibly an accompanying power spike) this morning.

Since then, the damn thing seems to power itself off after being on for between 21-24 seconds. Not really enough time to even boot the OS.

The hard drive and CD-ROM have both been disconnected. The fault remains.

I can go into the CMOS setup menus by pressing F1, but as sure as clockwork, after about 21 seconds, the power goes off again.

Any idea what could be the fault? I suspect the power supply, but I wanted a second opinion.

Paul.

[NathanAllan]

Testing the power supply may prove fruitless, cause there's really no load when using a multimeter. So I have to agree, first step would be test the power supply by using a different one. Still use the multimeter, couldn't hurt. If there are fluctuation, that could be it.

There's also a chance that the power circuitry on the laptop has been damaged. Changing out the power supply will also give you a hint about that, too.

Nathan

[barythrin]

A lot of systems will do that if the CPU is getting too hot. Might check fans, or heatsink/CPU sensors. Also could be a battery issue I guess, old laptops used to have this overcharged bug where they won't turn on with the battery in (not the same as your issue but always worth a try removing whatever part you can from the equation and seeing if it still occurs).

[paul.brett]

The Presario is a desktop PC. I should have mentioned that first time around.

[barythrin]

Ok, then definitely check the heatsink and heatsink fan and make sure that's working. An overheating CPU will usually power the system off just as described.

[dongfeng]

It certainly sounds like a heat issue. Is the fan spinning in the PSU? In this case, try another PSU to see if the problem persists.

And buy a surgeproof plug strip!

[NathanAllan]

It sounded like a laptop, okay, now I know. Check out the heatsink on the PSU, I ha da problem that the thing had come loose and shut the computer down after about a minute. So Barythrin's right on.

Nathan

[Druid6900]

I just replaced the power supply in a Dell something or another where the house was hit by lightening. It was plugged into a surge suppressing power bar. Guess they don't expect a surge quite that large :)

Anyway, funny thing was that some of the supply voltages were good (like +5 and -12), but, the rest were MIA.

[paul.brett]

OK, so I bought and fitted a new power supply. Same problem. Approx 24 seconds in, the computer shuts down.

I'm going to try and re-apply the two heat sinks with new heat transfer compound next.

If that doesn't work, I'm going to get annoyed with the damn thing, and chuck it out the window.

Paul.

[paul.brett]

Unfortunately, the thermal compound has not worked either, so I'm going to have to buy a replacement PC, and strip this for parts.

FYI - In the setup screen, the CPU temperature shows as hovering around 15°C / 59°F.

Some proper diagnostics would have been nice. Thanks Compaq!

Paul.

[dongfeng]

Weird! In this case, you can only substitute spares one at a time to see what is up. My guess is the mainboard... so scavenge away!

Edit: Just a thought... why not try a BIOS update?

[Druid6900]

Weird! In this case, you can only substitute spares one at a time to see what is up. My guess is the mainboard... so scavenge away!

Edit: Just a thought... why not try a BIOS update?

In 24 seconds? Shutting down in the middle of a flash is never good.

Take out any cards it might have (except video and you might want to try a video card if it has built-in video), disconnect any devices, go down to one stick or pair of memory and try it again. If you get the same thing, swap out the memory that you just had in there and try.

[barythrin]

Yeah, it's a take each part out and try it or reseat everything you can scenario to actually fix it. Look for buldging capacitors around the CPU and they can cause bad voltages on the board. But, building a new one can sometimes be cheaper when time is worth money.