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Making your own "+4" connector in a 20+4 setup

Last response: in Components
July 16, 2009 5:22:31 AM

Hi tomshardware people,

My PSU recently died on my desktop PC, and I had a friend who had an old PSU that he let me have to replace it with.

The only issue is that the new PSU that I got has a 20 pin motherboard power connector, but my mobo has a 24 pin connection on it. My PC works fine with the 20 pin connector plugged into the 24 pin slot with 4 empty pins leftover, however, this is unsafe; drawing too much power through the 20 pins can cause them to melt/ burn out. I really do not want this to happen, but I also really do not want to have to buy a new PSU just for the +4 connector.

To remedy this problem I am considering removing the "+4" plug from the old PSU's "20 + 4" connection.

Next, I plan on cutting the end off an extra serial ATA power connector and taking it's wires, then splicing them to the "+4" plug from the broken PSU. The reason why I am thinking of using the Serial ATA power is because it has 5 wires: +3.3v, ground, +5v, ground, and +12v.

The last 4 pins of the 24 pin mobo power connector are:
+3.3v, ground, +5v, +12v

As you can see, the wires in a SATA power connector and the wires of the +4 portion of the "20+4" connector are the same voltage with the exception that SATA has an extra ground wire.

Now here are my questions:

Do you think it would be safe to splice the SATA power wires into the +4 connector's wires to effectively create my own 20+4 connector? I plan on connecting them using those splicing caps from the hardware store and some electrical tape.

What could go wrong? Is it unsafe / dangerous / likely to cause a fire?

Also, what should I do with the extra ground wire from the SATA power connection? Should I splice both ground wires from the SATA end to the one ground wire on the +4 connector?

Is there anything I didn't think of? Any unforeseen issues with rails or anything else?

And lastly, does anybody have any suggestions for a better way of doing this, a better connector to cut/splice with, an easier way, or any advice at all? Im tight on money so Im really trying to avoid buying another PSU. Im a DIY cheapo.

I'm not an electrical engineer, but I have a CompTIA A+ cert. and plenty of experience with fixing computers and other various electronics.


OKIA PSU, 500W MAX output
(+5v & +3.3v combined load 230W)
(+5v, +12v & +3.3v Combined Load 422W)

AMD Athlon X2 6000
4 GB DDR2 800
GeForce 9800 GTX+ (1GB VRAM)
300 GB 7200 RPM SATA HDD
Super WriteMaster DVD-RW/CD-RW

3 Casefans + Heatsync

More about : making connector setup

a b ) Power supply
July 16, 2009 5:50:00 AM

I think you will be creating more of a practical safety hazard splicing wires than the one you believe you would be fixing.
July 16, 2009 6:09:46 AM

Considering your setup, you don't need the extra 4 pins. Far higher powered systems run off of 24 pins just fine (more than double the power though just 20% more pins). You're fine as it is, and you would probably cause more problems than you would fix by attempting to do what you are suggesting.
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a c 144 ) Power supply
July 16, 2009 6:37:52 AM

I vote with cjl. If it is working fine, check the connector by touch. If it feels no more than warm, leave it alone.

The extra wires were added because motherboards started drawing more power. The 4 pin EPS plug for the CPU had been added, but the video card was still powered from the motherboard. Now, the two items drawing the most power have dedicated power plugs. A "typical" computer does not really need the 4 extra pins any more.

Based on your system specs, your motherboard is not going to need more than 4 or 5 amps at 5 volts (motherboard logic), 6 amps at 3.3 volts (memory), and 2 or 3 amps at 12 volts. The motherboard itself will use very little 12 volt power.

I was in the same situation early this year. The 7 year old household computer died. I kept the case, drives, and the old 400 watt Antec power supply (20 pin main power plug). I replaced the motherboard with a G43 (integrated graphics) and an E5200 CPU. Main power plug runs completely cool to the touch.

Don't worry about the missing pins. You are likely to cause more problems that you are solving.
July 16, 2009 7:48:11 AM

if it works don't try to fix it, your solution will likely cause more problems than it helps
a b ) Power supply
July 16, 2009 4:41:25 PM

Concur with previous post.
If you opt to do it - You MUST use the same Rail as the 20 Pin uses (Not a problem with single rail PSU). As you know you can parallel to batteries that have the same voltage rating (ie 9 V) not so with PSU's With batteries if the voltages are sligthly differnent on battery will source current thru the other battery until ther voltages are identical. Power supplies will never equalize.

You would need to (With all Power supply connections disconnected) measure the +12 V pins on the 20/24 pin to each other. will find that they are shorted on the mother board. Measure the +12 V on the PSU 20 pin connector to the +12V pin on the connector that you plan on using - If it's a short - OK

Could be all wet
July 16, 2009 9:56:39 PM

Thanks for the advice everybody. I wont be making any changes to my rig.

I'm really glad I asked you guys before going in and "fixing" it, I just had a feeling I may be making a huge mistake.