Ongoing threads about Power Supplies has inspired me to copy and post this:
The following is from the FAQ, electronics repair group, I think....
4.16) Making a bench power supply from a PC power supply The power supply from a long obsolete PC can be the basis for a low cost unit useful for a variety of design and troubleshooting applications. The typical 200 W PC power supply will provide +5 V at 20 A, +12 at 8 A, and low current -5 V and -12 V outputs.However, these are not that well filtered - at least not where low noise analog circuits are concerned. They are fine for digital and power circuits as is. For analog work, additional post regulation (e.g., LM317s) and filtering may be needed.
- Typical (but not always) color codes for PC power supplies: Red: +5, Yellow: +12, Black: Gnd (Probably case as well). White: -5, Blue: -12, Orange: Power_good (output). (Some newer supplies may have a +3.3 output as well which may be green).
- PC power supplies (as well as most other switchers) need a minimum load on +5 and possibly on +12 as well. An amp (e.g., 5 ohms on +5) should be enough.
I use an old dual beam auto headlight. It adds a touch of class as well to an otherwise totally boring setup :-). You can also use auto tail light bulbs or suitable power resistors or old disk drives you don't really care about (you know, those boat anchors).
- There are no sense lines. There is a 'Power_Good' line which is an output from the power supply to the mainboard and can be ignored unless you want to connect it to an indicator to let you know all the outputs are within specs (it may need a pullup and I don't know its drive capability).
- Pinout for the standard PC and clone connector (some companies like Compaq do NOT use this type of connector, however.). Black (Gnd) wires together for the P8 and P9 connectors when installed to mainboard. J8: Pin 1 = Power_Good J9: Pin 1 = Gnd Pin 2 = +5 Pin 2 = Gnd Pin 3 = +12 Pin 3 = -5 Pin 4 = -12 Pin 4 = +5 Pin 5 = Gnd Pin 5 = +5 Pin 6 = Gnd Pin 6 = +5 Note: for an XT only, J8-Pin 1 is Gnd, J8-Pin 2 is no connect.
- The peripheral connectors are: Pin 1: +12, Pin 2 and 3: Gnd, Pin 4 =