While I make a mental note of the solution, I also continue on my rigid diagnostics until I have a confirmation. More times then not I could have gone with my instinct instead. There is value in having a solid reason for your action other then "My gut tells me its this..."
Take the issue with one of our Library systems. It's a Dell Optiplex GX260, which is a good workhorse of a computer. It has great accessibility of the innards where I can get my meat hooks inside with ease. This particular machine is used to create flyer's and pamphlets. It uses an easy to use graphics program, with a Color printer and a SCSI card hooking it into a CD-ROM changer (Yes, this system has been around quite some time). The CD-ROM changer is actually decommissioned as we are using a CD emulator to hold the various graphics libraries.
The issue? The system will not post or boot. Posting is what you first see when you start a computer, usually a logo for the manufacture or something that says Bios or Set-up or CMOS or whatever. This is followed by the Operating system (OS) displaying as it loads. A colorful logo screen that says Windows, or MAC or a penguin (don't ask).
Diagnostically there are some lights on the front of the system. When they are different colors it is a clue as to whats going on. In this case the light was green, which was no help.
The computer gets power and the power reaches the mother board and the other devices, yet the system does not post: bad power supply, or bad power cord. I grab a cord from the huge pile any IT person has and viola! It starts up fine! EASY fix, I cut the old cord and put the system back. Bad news, next time it did not start up. Two bad power cords is unlikely.
So I haul the system back to my table and IT WORKS! I shut it down and try it again, It works. Okay... I head back to the desk plug it in and no work... I plug it into a different wall socket. IT WORKS... once.. I plug it into a different wall socket. IT WORKS.. once...
I pull out the multi-meter and check the power. It's all per specification. I haul it back to my desk plug it in and NO POST.
Okay this has got to be the power supply. Its pooched. So I order a new one and wait.
A few days later it arrives and I swap it out then try to fire it up. No Post No Boot. WTF??!!
This time no cable or socket will let it start. Bad New power supply? Meter says its fine.
Then the depression hits. I fixed a computer from partial functionality to no functionality. I'm just thinking I am too close to the problem. So I talk to the other tech's and they are perplexed as well. oh joy...
Time to work on something else. I slunk down in my chair and begin updating our intranet wiki page. I get the code setup in notepad then goto the different pages edit and move on. Then as I turned my head and looked at the misbehaving PC, sudden inspiration took ahold of me.
I yanked the power cord, pulled the SCSI card, plugged the system in and hit the power button.
IT Started up perfectly. I did a shut down then restarted three more times. No problem at all.
Now I'm a mixture of happy and stupid...
All computers have a power supply, these are all rated at certain wattage's. You really want as much wattage as you can reasonably get, unless your Dell... Dell has a habit of using just enough wattage to get by without issue. SCSI cards use a good bit of power, just enough to brown out the system. Think of it as the proverbial straw during camel torture.
Why did I feel dumb? When I worked for Dell the bigger flat panel monitors started to arrive. This prompted people to buy them and install them only to find the wide aspect would look "funny", this was due to the older graphics not being able to handle that aspect ratio. (the old graphic cards could only display the more square picture and stretched to fill the HD size picture).
The solution? Get a new graphics card! The problem, that old power supply cannot pump the needed power. Final answer, return the Monitor and Graphics card to Dell. Seeing as how returns are hated, I started firring off missives to anyone who cared showing them that you cannot just send out any old graphics card to any old PC.