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How to test my PSU connector voltage with a multimeter

Last response: in Components
May 23, 2012 1:09:42 PM

Hey there,

I'm upgrading my 8800gt card (1 x 6-pin connector) to a gtx 560 (2 x 6-pin connector), so it's going to be drawing more power. My PSU is a 1000w unit which came with my dell t7400 workstation, so in theory should be no problem.

Before I connect the 560, I want to be sure that it's outputting the correct 12v voltage for the card from each 6-pin connector.

Here are diagrams of the connectors from my system user manual:

And here is a photo of the multimeter I have:

Having never used a multimeter or measured voltage, I could really use some advice please:

1. where should the red and black leads plug in?
2. what setting should I put the dial on?
3. what is the process for testing the voltage on the pins for those connectors?

The more detail the better, really don't want to fry anything or myself!

Thanks in advance :) 
a b ) Power supply
May 23, 2012 1:29:42 PM


This link gives the color codes for ATX power supplys

yellow wires for +12V (+-10%) (red lead on meter)

black wires for ground (black lead on meter)

set meter to DC voltage any range above 16V

if you have a spare 4, 6 or 8 pin pci express connector (intended for graphics cards) or
molex connector (connects to disks) connect meter leads to one of these connectors

but this can not guarantee a PSU works at a higher load than tested at
check 12v voltage current rating of power supply and current & future graphics card

If your PSU is a genuine 1000W it will work with almost any retail graphics card and probably two

Mike Barnes


Mike Barnes
May 23, 2012 3:18:12 PM

Ok thanks for that info Mike, sorry if I am being a bit dense, electrical testing isn't my speciality. I just had a couple more questions to clarify.

1. there are 3 slots on the multi-meter, which one is for the black lead and which is for the red?

2. so the dial should be on DCV 20? (per the photo of the meter)

3. do I put the black meter lead tip on a molex connector pin which is on the end of a black lead?

4. do I put the red meter lead tip on one of the 6-pin connectors (pins 1, 2, 3 in connectors P18 or P5) in the diagrams in my original post?

Related resources
a c 243 ) Power supply
May 23, 2012 3:30:08 PM

1. Black to common, Red to V,ohms,mA
2. Yes
3. Yes, or the black wire in the 6 pin connector
4. Yes
a b ) Power supply
May 23, 2012 3:41:30 PM

First, that's a very inexpensive meter so don't expect too much from it. Plug the black lead into the "comm" slot on the meter and the red into the one just above. Do not set the dial above 20VDC. Higher settings will affect the accuracy. When the supply is running with the connector not plugged into anything you may see a voltage higher than 12VDC. That's because there's no load. It's easy to access the connector pins when the connector isn't plugged in as you describe. I would also check the voltage under load by inserting the probes into the connector pin cavities from the rear. Just be careful not to slip and break something or touch something you shouldn't.
May 23, 2012 7:32:56 PM

Thanks v much for all your info folks, I think I have enough to give it a try now.