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PC won't boot

By truman ·
Came home today to find my PC had shut down. When I try to power it on I get nothing. I press the power button and nothing happens. When I turn the power off then back on at the mains, then power the machine on the lights flicker, the fans run for about half a second, and I get a green light on the motherboard... nothing else though. Pressing the power button again has no result at all, though the light on the motherboard stays on, but powering off/on at the mains again will restart the same process as above.

I have not added any hardware, I've tried reseating all hardware, cables etc. Same result. I've removed all power leads to the HDD, CDRW, floppy drive. The machine still won't power on further than the half second.

Any ideas before I replace the power supply?

The PC is only one year old - Athlon 2000+, 256Mb of RAM, 60GB HDD. Running XP home edition.

No warning before any of this happened though the machine has been locking up for brief periods of late, generally only for a few seconds or so.

Many thanks.

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by TheChas In reply to PC won't boot

Might be the CPU.

Or, even the motherboard.

The green light on the motherboard informs you that the 5 volt "standby" power line from the power supply works.

If the power supply itself was dead, that would not be there.

On an ATX style system, when you press the power button:
A circuit on the motherboard sends a signal to the power supply to turn on full.
After the power supply turns on, the motherboard has a few seconds to send another signal to the power supply that all is well.

If the CPU is dead and loading down the on-board regulators, the "power good" signal will not be developed.

The same will happen if the power control circuit on the motherboard itself has failed.

Start by removing your modem and / or network card.

The above said about system power, it is not impossible that the power supply has a problem.
Since it is a lot cheaper and easier to change the power supply, that is as good a place as any to try next.

Next, swap in a different CPU.

If the system does not immediately power up with a new CPU, you may need to reset the CMOS.
AMD CPUs are notorious for not powering up if the CPU clock is set wrong in BIOS.
Depending on your system, you may need to both set the clear CMOS jumper and remove the CMOS battery to get a chance to boot up with a new CPU.

If that does not do it, you need to decide if you want to swap in a new motherboard.


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by dmiles In reply to PC won't boot

Have you expierenced a power surge of any type that could have caused this problem or the cpu may have over heated
You could try booting with a startup disk,but at this point you may go ahead and check the power supply power leads with a multi meter,if not available then you should try replacing the power supply

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by BbBucko In reply to PC won't boot

Resetting the CMOS/BIOS is the first thing I would try but tends to only sort out issues temporarily and is a good sign that your CMOS battery is on the way out - don't think that's your problem though, your machine does not sound old enough.

Power supply is a good candidate but I've had lots of trouble with faulty video cards of late causing exactly the same symptoms that you describe but you did not indicate whether or not you had an AGP card or a mobo with integrated video. (check if the heatsink on the vid card is caked in dust - biggest killer!)

If the BIOS does not find a working vid card then it says "what's the point of booting?"

I'd try swapping out the vid card first and then the RAM before swapping the Power Supply out. If you still have no joy then sadly it's probably the CPU and/or mobo.

Good Luck!

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by rbmccall1 In reply to PC won't boot

Before you spend any cash, remove the cpu & try to power up. The fans should come on. If that's the case, you may need to replace the cpu & mobo. I've had this problem twice with amd's because hey run hot.

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by RCOM In reply to PC won't boot

A year is just enough time for the cooling fan to slow down enough till it's not doing the job. The CPU overheats and fails. Often damaging the motherboard along the way. This is why I quit buying AMD CPUs. I don't want to start the which CPU is better aurgument so I'll leave it alone.

If it's not over a year or real close you may still be under warranty so check into that.

For troubleshooting and testing plug directly into a known good wall outlet.

As mentioned when the unit is plugged and the start and stop of the fan and 5 volt indicator light being on is normal.

Just in case you're lucky and the front button is out disconnecting the cable and jumper from the power button to the jumpers on the motherboard. Use a tip of a screwdriver to physically short the pins and see if the system starts.

Disconnect all but the mother board from the power supply. Reseat the CPU, RAM and video. Remove all other devices. And see if the system comes up.

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by bellucci In reply to PC won't boot

I've experienced a bad cd rom drive giving the same sympthoms, once replaced the computer booted up as normal.

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by lwalden In reply to PC won't boot

Sounds like the Sasser virus. I had a laptop with XP on it and it had the same exact symptoms. Luckily I had another pc and was able to get to the internet and print out instructions on taking care of this. I went to the microsoft web site and went from there. Good luck.

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by cliffg8 In reply to PC won't boot

I start by removing all interface cards and peripheral cables from the motherboard. If the computer boots, add the cables etc. back one at a time. Boot between each install. This will help find if some interface card failed. If the board doesn't boot or at least give you a beep code that there is no video card you have either a bad motherboard/ cpu or bad power supply. You can do a quick check of the power supply by checking if the hard drive spins up when power is turned on. You could still have a bad power supply even if the drive does power up. I have an interface card that plugs into a slot that will check the voltages and show the boot progress of the motherboard. Good luck.

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