Converting an old ATX PSU into a bench PSU

Electric Rain · Post by **Electric Rain** » Fri Sep 12, 2008 1:23 am

I'm sure you've all heard of it; some of you have probably already done it. Well, I'm having problems. It's a simple project, very simple... I'm not asking for help with the project itself. I think there's something wrong with my power supply. But maybe someone can enlighten me. See, the voltages are all off, and I was wondering if there was a way to either adjust them or something. I dunno... just look at my "chart" below...

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Red    =  5.8V     5.0V  (0.8V over)
Orange =  3.0V     3.3V  (0.3V under)
Yellow =  9.9V    12.0V  (2.1V under)
Brown  = -7.9V   -12.0V  (4.1V under)
Purple =  5.0V     5.0V  (SB)
Blue   = -5.0V   - 5.0V
White  = PWROK
Black  =  0.0V

Yeah, it's using some odd color coding, but it is in fact an ATX PSU. Anyway, the first number is what I'm getting with my multimeter (which I'm pretty sure is accurate), and the second number is what the voltage is actually supposed to be.

Can anyone make sense of this? Please?

kasar · Post by **kasar** » Fri Sep 12, 2008 4:14 am

mmm, you got undervoltage?

when I did that mod to my ATX PSU,all you need to do is bridge the green wire to a black wire, (It worked for all my atx suplies),
if that doesnÂ´t work, or you need more info, visit those sites

http://www.burningissues.net/how_to/power/theory.htm
http://www.wikihow.com/Convert-a-Comput ... wer-Supply

if you still having wrong V values ,maybe you are shorting wrong pins or something wrong, or maybe your atx suply is crapped.

kasar · Post by **kasar** » Fri Sep 12, 2008 4:30 am

Double post, srry

Electric Rain · Post by **Electric Rain** » Fri Sep 12, 2008 6:25 am

Yeah, green is shorted to ground and all of that. The sense wire also had to be tied to 3.3V (Sense wire is almost always brown, right? This thing is so odd, it was orange; the same color as the 3.3V lines!

)

I've done everything right... it's just not kicking out quite the voltage it's supposed to on most of the lines, and putting out a bit too much on the 5V line.

Rekarp · Post by **Rekarp** » Fri Sep 12, 2008 7:07 am

1. Its probably a cheap PSU
2. It is not under load

techknott · Post by **techknott** » Fri Sep 12, 2008 8:54 am

Try shunting each of the lines with a resistor(to ground) to simulate being under load.