Well there are lots of detailed manuals on the web describing how to turn an AT(X) into a bench power supply. Here is a few:
I'm using an old "converted" 200W AT myself. It works great. It wasn't much of a conversion though. I just seperated the wires according to their colors, and soldered the AC power connection to be permanently ON. It provides a steady 5V (up to 20A) and 12V (up to 8A). It also has -5V and -12V should I need it some day. I also bought some banana sockets and a switch so when I get around to it I'll be making a nice panel for it. But for now I'm using it as is.
The newer ATX supplies generally requires a minimum load to function though (mine doesn't). So you'll need a 10 Ohm 10W power resistor attached to one of the 5V wires and ground. This can also be used to discharge the caps, however it is recommended to let it rest for a few days so the caps can discharge themselves.
If you need a cheap, steady, reliable power supply capable of more than a few amps, nothing beats an AT(X). The only drawback I can think of is the FAN. A bit annoying. I'm thinking of detaching it, but I'm afraid the damn thing will overheat if I do so...
What do you guys think? Would it be safe to detach the fan? The thing is: when using an AT(X) in a PC it functions as a vent for the entire PC + a PC draws more power than I'll ever do so perhaps it would be OK?
Agreed, a walkthrough would be awesome.. I got a couple power supplies I want to tear apart!
Just one question, does anyone know how to "Safely" ground a power supply? I know it often has alot of power in the capacitors and what not, I'd rather not tear it apart when it's "alive". Is there anyway to get all the power out without killing myself? :)
I never realized how many amp's were in these things until I looked.. my power supply has 14 amps coming from 5v.. how useful.. and scary! :)
Short the DC outputs with anything that will offer some resistance and can take a bit of current without smoking.
For example the 12V output: to short it with no more than half an Ampere, you would want to use a 24 Ohm resistor. Round that up to the nearest value you have in stock. Make sure the resistor is rated to take half an ampere or more. At 12V that would be about 6 Watt. That's a lot of power. Most resistors are rated at 1/2 or 1/4 Watt.
Maybe you can use some sort of power using device, like a light bulb, instead. I once used a piece of pencil core / "pencil lead" as a resitor to discharge a battery. A 20 mm piece would take 1 Ampere from a 3.7 V battery.