Adding a second ATX Power supply to my PC

Well, after a long time pondering the constant crashing and other problems I’m been having with my PC over the last year, I decided to try and fix them and this one mod (although not too big) fixed all but the noise.

The main reason is that my video card sux too much juice, making the sound stutter and causing the memory and hard drives to lose data.

Warning!
Before you start hacking your prized PC apart, besides running the risk of killing you comp for ever, there is a small chance that you could kill yourself in the process. So if you’re not sure what you’re doing, don’t do it. I have been building and moding PC’s for 15 years.

My comp is a mish mash of old and new parts, (I’ve had the floppy drive for as long as I can remember). Put together as follows.

AMD 2800 XP Athlon
Abit KW7 main board
4 * 512mb pc2700 333 DDR Ram
1 * 70G HD
2 * 80G HD SATA Raid
1 * 40G HD (Linux)
1 GL DVD/CD Burner
ATI 9700 pro

Up until I began this project I was using a 300w PSU, and was having big problems with burning out main boards, I traced this to the fact that video card, along with the hard drives, was pushing the PSU to its limit.

Time for an upgrade! I looked around to find a suitable replacement in a single PSU, but found none within my price range, ($50) So I opted to buy 2 generic PSU’s from a guy on e-bay ($20 each). They are not the best, but the two gives me a total of 800W, and as it’s the first time I’ve done this, I guess it’s best not to waist too much cash on something I may just end up frying.

Before I go on, a few recommendations.

Remove all the cables from your computer and place you comp on a wooden or plastic table, not the floor or carpet to avoid static and dust. (Anti static mats and wrist straps should be used if you have them, when handling your PC’s special parts).

Thing’s you’ll need if you want to follow along.

2 ATX Power Supplies
1 x 20 pin Molex connector female
1 x 4 pin Molex connector female
Wire (Black, Green and Yellow)
12vdc Relay (4 or five pronged)
Soldering Iron
Solder and flux
Wire stripper
Cable Ties
Philips screw driver
Electrical tape and heat shrink tubing

Ok, let’s begin.

It was easy for me to start this project, as my pc was already stripped down. (Having blown the main board last month; until my new one gets here, I’m using an old Asus A7V8X-x.

I put this in an old 4/4 case (4 x 5 inch & 4 x 3.5 inch bays). Along with some old ram, hard drive and AGP card, just so I could see the layout and decide where the second PSU would go.

Open your case and take a good look inside. (Don’t touch anything unless you have to) Before you start tearing bits out, look to see where would be best to put your new power supply.

After playing about a bit and assessing the locations I decided on placing the PSU in the front of the case, under the 3.5” bays. Looking around the web, I have found most people who do this end up placing the new PSU here. It seems to be just about the only spot.

If like most you have decided to install you PSU in the front of your case under the drive bays, you now have to figure out how are you going to;
1 connect the power cable from the mains,
2 where to put all the extra cables
3 how to secure it in the case
4 what to do about all the hot air the PSU will produce
5 what you want to plug in to your new PSU

Note:
This spot is not designed to house anything other then a 2” speaker or an 80mm fan in nearly all cases.

Now that the location for my PSU was set, I found that the new PSU’s vents did not line up with the hole for the 80mm fan, no mater how I tried. Fortunately I had an older PSU that, upon closer inspection, I found to fit almost perfect. Allowing me to draw air in from the front and feed it out the right side of the case without mixing with the air in the case. This Older PSU I found to be dead, so I set about changing the cases about. (Not recommended if you spent a lot on your PSU. Try and find one that can take in air via a number of vents.

While I had the PSU open I soldered an old power cord (removed both ends) to the inside of the power connector. This I will use later to add a second power socket to the back of the case. Get a grown up to help you if you don’t know 100% what your doing. 110/240V can kill! (Not covered in this tutorial yet.)

Depending on your PSU, the air intake and outlets may differ from the one I’m using. You will have to mess about a bit until you can get it to line up so that it can use the hole (that’s in most cases) for the PSU’s fan to take in air through the front of your case.

Once you have aligned your PSU look and see if there are any ‘convenient’ mounting holes.

The case I’m using has a 80mm fan grill but the PSU, has only a large grill on its base, and the 80mm fan on the back (standard)

To over come having to drill holes in the case and PSU to mount it, I snipped out a couple on the small bars on the PSU and bent them so they would slide through the holes meant for the plastic fan mounts (often found in higher end PC cases).

This worked a lot better than I first expected. The PSU sits flush with the front of the inside of the pc’s case, and is secure enough not to require fixing further.

Not wanting Murphy’s Law to come in to play I decided to put a couple of screws in the only holes that did align.

Note:
After finishing this project I decided not to cut the hole in the side of my case, for 2 reasons; 1, I have enough holes in it already, and 2, the heat put out by the second PSU does not seem to increase the over all case temperature.

In-fact, I have noticed that after long hours of gaming, the case is about 5c cooler (±2c).

Now it’s time for a cup of tea while I think about how to wire the two PSU’s together.

To do this I made a set of cables that allows me to 1, switch out both PSU’s and the relay, without touching the main board, and 2, hide all the cables in the front and side (behind the drive bays) of the case. Making are flow a breeze (I know, lame pun).

To do this you need most of the other stuff listed at the start. Then just follow the diagram below:

Start by finding a spot for the relay.

I attached it to the back of the drive bays. A bit of a squeeze when the back of the case is put on, but it’s out of the way. Placing it here also helps hide all the wires.

The wires from 4 to 5 in the diagram should be made as short as possible, while 3 to 4 should be left longer in order to reach 2. (Make sense? Hope so...)

The connectors on the relay should be standard and can be connected with solder. I chose to use slide connectors and shrink tubing, no solder involved, and easily removed.

Make sure all other connections are soldered.

I’m sure you can figure the rest out from the diagram above.

By doing it in this way, I'm able to replace all parts if needed, without tearing my whole PC apart.

Once all the soldering is done, decided what you want to plug in to each of your PSU's.

I chose to plug my primary HD and SATA drives in to the main PSU, and my video card and cooling in to the second. I thought about this for awhile, and was a bit nervous about doing it this way, but it's been working fine.

Now, the only thing left is to plug it in turn it on and dive behind the sofa and hope for the best.

Chances are if your PC is pretty new, and you make sure you wire it right, everything should be working fine.

Here are some pictures I took after the project was completed. Next time I clean this beast out I'll take some closs-up's of the relay and adapter I made so that both ps' can be removed with out tearing the whole thing apart