24 pin Connector Empty Pin

TruisticHurdle1 · August 17, 2016

Have a corsair cx600m and EVGA 550G2 power supply and both have the empty(white) pin/connector in the same place. (Five slots up from right if clip is on right)

I am putting together a new build and my cablemod replacement cables have the white empty pin in the wrong place.

My PC wouldn't post and flickers on for 2 seconds and auto restarts. Weird clicking from power supply. Now board won't turn on. Did it fry my motherboard?????

mariushm · August 17, 2016

The empty pin used to have a wire giving the motherboard -5v , which was last used in ISA slots (the slots before PCI). The latest ATX power supply standards (every standard since sometime around 2012 or something like that) say that this voltage is no longer required to be supplied to motherboards and that motherboards shouldn't expect to be there anymore.

On one side of the pin you have ground and on the other side you have 5v. If the motherboard even connects that -5v pin in the connector to something, it's probably connected to ground. If that's the case and if you're unlucky and those guys screwed up and put one of the +5v wires in the empty place, then you probably shorted the 5v to ground (the +5v from the power supply makes a direct connection to ground pins through the motherboard), which would trigger the power supply's protections and prevent it from powering up.

The motherboard really shouldn't be screwed up if you sent +5v on that -5v pin... seriously doubt anything on the motherboard is used -5v these days.

TruisticHurdle1 · August 17, 2016

Here is what the Cabled 24 pin looks like. Maybe switched with a 3.3v?

mariushm · August 17, 2016

Yeah, that would correspond to a 3.3v rail. The motherboard should work with one of those 3.3v pins missing, it doesn't draw so much current on 3.3v that would require 4 x 3.3v wires.

Best thing you could do would be to grab a digital multimeter and measure what you have on every pin. Just plug that cable in the power supply, use a wire or a paper clip to connect PS_ON to GND (connecting the two tells the power supply to start up) , then put the multimeter on DC voltage and use the black probe on any GND contact and the red probe you can use to measure each contact.

Even a $2-3 multimeter would be enough for this.

As for extracting those contacts without specialized extraction tools (original molex ones are around $60) , I heard you can extract those contacts using regular staples (i think 1/4" ones). Basically the advice i was given was to take one of those bars of staples and break two pieces of two staples each (or maybe more, but try with two first), insert the two sets on both sides of the metal contact as far as possible and then pull on the wire and it should come out, Apparently, turns out the thickness of the regular staples is about the same as the thickness of the extraction tool on both sides.