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Premium Member
8,743 Posts
Discussion Starter · #1 ·
How to use two Power supplies on one computer.
Difficulty rating Moderate

Ok let me start off by stating that many of us have old power supplies laying around our house. This guide will give you step by step directions to use that spare power supply unit [PSU]. Why would you want to have two PSUs anyways? There are many reasons to have multiple PSUs for your computer. One reason is to take the load off of the PSU that supplies power to your Proceesor, thus allowing for better stability for overclocking. Another reason is so that you can power up other 12volt items without your computer examples being Peltiers, Cold cathode lightuing, external fans, and so on. One more reason is that if you have a generic PSU and need power for your new high end graphics card, you can dedicate a spare PSU to run only that item. Over all there are many reasons to have some extra power on tap, I am just going to help you get that power really cheap

1 Spare Power Supply
2 Male pins [ need to fit the 20pin PSU molex]
1 piece of 16 guage wire 2-3 inches [5-8cm]

Optional supplies
1 Single Pole Single Throw switch(SPST) "Push On-Push Off"
1 4pin fan or light "for testing purposes"

Tools Needed
Wire cutters [needle nose pliers work as well]
Wire crimpers [needle nose pliers work as well]
Pin insertion tool [needle nose pliers work as well]
(If you couldnt tell all i used was Needle nose Pliers)

Ok now on to the Fun part, Modding the PSU

Step: 1 Cutting the wire

Ok now take your little piece of wire and strip the ends off.
Your wire should look like mine in the picture below.

Step: 2 Making your Jumper

Take your Male pins and with your needle nose pliers crimp them onto the wires on both ends so that you can just bend it around so that the pins can touch each other.

Step: 3 Jumping the PSU

Here is the tricky part, We need to find the Pins that the Motherboard uses to turn on the PSU. On most PSUs the wire that turns it on is Green wich needs to connect with a ground Black. I have created a image that shows what all the different wires do on the 20 pin connector, and have pointed out the Power on [PS_ON#]and the closest ground [COM]. We will use our jumper to connect them together.
Below is the image showing where the pins are located, the clip is on the right in my picture.

STEP: 4 Connect the dots

Ok so all you have to do is this, with the clip to your right count 4 pins up and place your jumper in the 4th hole on the right side. Refer to image above for pin locations.

Then go ahead and take the other end of the wire and conect it to the fifth hole, Right above the one you just inserted, it should look like the image below. Refer to image above for Pin locations.

Thats it now plug in your fan and turn it on to make sure it works.

Alternative Steps
Installing a on off switch to turn on your PSU.

From step 2 instead of creating a jumper do the following. Take a Single Pole Single throw(SPST) "Push on Push Off" switch, And install wires to the switches posts. And on the ends of the two wires install the Pins. Then follow step 4 above to insert your switch into your PSU. Should look something like the image below.

Now that that is done you can mount your switch anywhere you would like it to be on your case.

If you are having trouble with any of these steps please PM me and i will be happy to help you..

If anyone has any suggestions for this guide please let me know and i will try to add it as soon as possible.


Premium Member
8,743 Posts
Discussion Starter · #12 ·

Originally Posted by tw33k2514
heres a good question does it work the same for 24 pin PSU's?
havent messed with the 24 pin PSU yet, so when i get one i guess i will have to figure that one out... but you may be able to find a diagram, and just find the power on and the ground, and the rest is the same..

Not positive but i think that the 24pin molex is identicle in molex shape it just has 4 more pins so if you follow the pin order you should be able to match them up..
20 pim molex has two different sockets in the actual connector, some are perfect squares and some are D shaped squares, that way you cant plug it in backwards...But im guessing not too many people have a 24pin PSU laying around

Premium Member
8,743 Posts
Discussion Starter · #17 ·

Originally Posted by digitalphreak
Provide a few ideas on where or how to mount your second PSU. Other than that its very comprehensive. I might give it a try since I have an extra HDD and DVD-ROM Id like to run.

Let me know if you hit any hickups during your install..
I measured the PSU its almost exactly the size of two 5.25 drive bays, if you could let me know if it fits
im at work right now, that would be awesome, but ventalation could be an issue. but i could prolly Draw up some mounting ideas, maybe even side exhuasting, but if you have a big case, then you could just place it on the bottome next to your RES and Pump..The drive bays sounds like an option. my new old case looks like i could fit 3 PSUs in just the space at the top of the case, along with BIX3 and a pump

But thats in the next guide...
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