So, to replace the computer I went out a bought the cheapest computer I could find after twenty minutes of searching a Best Buy. I got an e-machine.
A few months later I replaced the e-machine, and gave the e-machine to my sister.
Years went by.
Turns out my sister never used the thing and it was just sitting in my mother's attic.
I decided that it would make a decent media center machine. So, I took it apart, cleaned it out real good, slapped in a DVD drive and a wireless card, presto - chango - new really cheap media center. Great for playing avi files on my TV.
Now, the problem. (Because there is always a problem...)
Behold! A crude diagram of the entertainment setup in my living room.
Ok, so here is what was happening:
There is a hum in the audio. Not a subtle hum, but not a loud one either, just a hum.
The hum was not present before the computer was added into the mix.
The hum is present when listening to all audio sources EXCEPT the computer.
The hum is only present when the computer is plugged in.
So, being the adventurous type that I am, I took it apart again.
No lose wires...
So, lets disconnect everything from the power supply and then plug the power supply back in.
The hum is still there...
However, I now also have an odd feeling in my forearm, which happens to be resting on the inside edge of the case...
OH! I know that feeling. That's electricity!
Ok, so ... my power supply is improperly grounded....? I guess? Electricity is flowing through the metal parts of my case? That doesn't seem right....
Ok, remove power supply from computer. Power supply is now not connected to anything.
Plug in power supply ... no hum. (If there had been I might have started looking for a priest to perform an exorcism....)
Ok, let's plug the power supply into something.
Connect DVD drive to power supply. Plug in power supply. Hum returns.
Well, I definitely know what's causing the problem.... but I'm not sure why...
So, I took the power supply apart, and relocated the family of bunnies which had been living in there.
Nothing looked wrong... apart from some really sloppy soldering.
I put on my "old man" glasses so I could look a little closer.
Well... I'll be, there is a ground wire going from the circuit board to the metallic exterior of the power supply (at least I assume it was supposed to be a ground wire...)
So I rewire this ground wire so that it connects to the ground coming from the exterior.
Re-assemble.
Cross fingers.
Plug in.
No hum....
Connect (expendable) CD Drive.
Still no hum....
Reconnect everything else.
Still no hum.....
Power on computer.
Computer runs fine.
Still no hum.....
So, that's my story. I'm not an electrician, but I understand the basics. I still have some questions though...
What exactly was the problem? (if I had a multimeter of some sort I could have tested to see if the case was actually hot... but I don't have one of those...)
Are power supplies normally "grounded" to the case like that?
Did I do something horribly wrong and/or dangerous?
