I have run into the strangest computer problem I have ever encountered in all of my years messing around with computers. The computer is working — in all respects that I can see. I can go on net, run programs, read and write CDs, execute Windows functions etc. But the front case power LED stays on when the computer is shut down. The mother board is an ABIT IC7-G which I have used to assemble three computers, so it is a motherboard that I am very familiar with. I have another one in the laboratory at this moment, also working just fine, but with the power LED not exhibiting this strange behavior. Both machines are running Windows XP Pro with SP2 installed. I have checked and double checked — even comparing the plug wires with the one that is not misbehaving — and can not see where the two are different in any way. Thinking it might be power supply related I swapped out the Thermaltake Pure Power 420w that was in the case with a new Thermaltake Pure Power 480w, which just happens to be the power supply in the IC7-G system that is not misbehaving. Didn’t make any difference. I pulled it out of the case and assembled it on the bench, same result, the power LED stays on when the computer is shut down — not set to standby or hibernate, but a full shutdown. That means it is getting power somehow from the hibernate supply — but how? While on the bench, I stripped it down to only a graphics card and hard drive — with no difference.
Given the troubleshooting I have done, it is not the power supply, it is not a case short nor is it case related since when I assemble a computer on the bench I have a momentary ON switch on a short length of wire to turn the computer on and an LED on a similiarly short length of wire to monitor the status of the power.
The computer is definitely not in standby or hibernate mode. Neither moving the mouse nor pressing any combination of keys on the keyboard will cause it to come up. The only way to get it to turn on is to press the start switch after which it goes through a full bootup to come back on line. If I shut down the computer it goes through the normal sequence for shutdown and turns itself off. The power LED stays on as I have said, but there is another even more mystifying thing. It has two optical drives — a Benq CD/DVD reader and a K-Hypermedia 52x24x52 writer. Each of these drives has an activity LED that flashes green to show activity when the drive is in use. I hadn’t noticed before, but the K-Hypermedia LED glows orange when the system is powered down. The LED on the Benq is off when the machine is off. When the machine is turned on, both drive LEDs are off when the drives are not in use. In other words turning the computer off turns the LED on the K-Hypermedia on — to an orange state instead of the green it shows when in use.
As I mentioned above, I have another computer built on the same ABIT IC7G motherboard in the lab. They both have the same BIOS versions and both have the same two modules of OCZ Platinum series II memory. They differ only in the speed of the Intel Pentium 4 CPUs. I did a line by line compare of the BIOS settings in the two machines and they are set identically. I thought there was some remote possibility a BIOS setting (especially in the power management section) could be the explanation.
I have run out of troubleshooting ideas (for now) on this one. In all of my years of building and maintaining computers I have never encountered anything this inexplicable before. Just goes to show that there is always something new under the sun — where computers are concerned.
Any ideas. Here is your chance (and I would welcome it) to put me to shame in troubleshooting.
