Modify the atx power supply( -12V more than 0.8A)

[edi14_10]

Hi. I have a ATX power supply. i want to use the +5V, +12V, and -12V. usually the -12v is just 0.8A. I need more than this. maybe almost equal to the current of +12v(12A). Does anyone have any suggestion to modify the power supply so i can get this condition? thanks for the advise.

[marty.markoh]

Friend-this http://www.webx.dk/oz2cpu/radios/psu-pc1.htm  maybe help?! Or one in attach?

[pickit2]

Depends on your skill and the use you want to put the power supply to.
one way is to use two ATX power supplys, you need to remove the earth from the pcb
so you wire them as one unit.

with the earth removed you wire this.
-------------------------------------
psu-1 Black wire as -12 volt

psu-1 Yellow as common  zero volts
psu-2 Black as common with yellow from psu-1

psu-2 Yellow wire +12 Volt
for +5 Volt use Red wire from psu-2
-------------------------------------
other wires for psu-2 are as known with ref to common
the wires from psu-1 can be metered to show voltage.

[neelandan]

The waveform of the voltage at the rectifying diodes (of the computer power supply) is usually a square wave.  So if you can identify the two points where the +12 diodes connect you can connect two other diodes in reverse  and duplicate the filter arrangements to get your -12 V supply.

If the two diodes are in a single (double diode) package, you might need to use equivlently rated single diodes.