I've obtained a working computer power supply and I'd like to use it to power a car stereo system. The power supply provides 12 volt DC and 8 amps but I'm not sure what wires are used to switch the power supply on. I'm guessing the color coding is pretty much universal so I'm asking if anyone knows what I need to do to turn it on?

 

I've seen 2 different color wires used to turn computer power supplies on.
Green, and Grey. If you have these color wires, try tying each one to GND, and see if the power comes up. I've also modified the 12V on computer power supplies to put out 14V, instead of 12V. 14V is the normal "running" voltage in an automotive electrical system. This can also be used as a battery charger.

 

To keep it on you need a load on the 6v side, so use a tail light or something.. then you have about 5 amps on the 12v side. black is useualy common and black 12, yellow 6. sometimes its switched.

 

6V is not a common voltage for PC power supplies.

Here are some common voltages / wire colors:

3.3V ---- ORANGE
5.0V ---- RED
12V ----- YELLOW
-12V ---- BLUE
-5.0V --- WHITE
5.0V (standby) --- PURPLE
POWER-ON ---- GREEN (negative active, tie to GND to enable power)
GND ---- BLACK (for all supplies)

 

if you fri that one I got a whole box of them from dead pc if you want them 1 from a 286pc, 2 a AT system and 2 from a (pre P4)ATX sysem

 

Bob, thanks for the info. How do you bump up the 12v to 14v?

 

Bob, I just tried jumping the green to ground and all that happens is the cooling fan makes about one rotation then stops. RyanMiller mentioned that you need a load on a different voltage to keep it on. Does that sound right?

 

Most of the PC power supplies I have messed with don't need any external load to power up. The other possibility is it has some kind of remote "sense" that needs to be connected. Most supplies have small adjustments, but not enough to raise the 12V to 14V. I had to change some resistor values to get
the 12V to 14V, and I also disabled the other voltages (5V, 3.3V, etc.) to give me more current from the 12V. E-mail me the manufacturer, and model number of the power supply you have, and I'll try and find the schematic for it, to tell you where to go from here.....

 

Bruker, you will need a load on all sides of the supply to make it work. I suggest an old hard drive or similar. I've had the same problems you are having. Luckily I had an old MFM hdd (who remembers those?) that did the trick quite nicely.

 

Here is a site that may help. Has pinout information covering AT,ATX, and ATX-2 power supply types.

http://www.helpwithpcs.com/courses/p...nc-pinouts.htm

I have been using an old AT type to power some of my projects with good success, and it powers up without needing any artificial loads, but I also have heard that some MAY need them.
Dialtone

NOTE: Some Dell ATX power supplies DO NOT conform to the standard ATX pinouts on the motherboard connector, but still supply the standard voltages.

 

I actually had one of the old XT/AT power supplies that needed a load to run. It was the only one I ever saw.

 

I've always had to have some kind of marginal load on the PS to get them to come on when bench testing them. I use a junk CD-ROM drive for the task.