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Could anyone tell me if and how i might verify whether or not a PCI-Express 6 pin power lead on a PC is outputting correct voltage(s) ?

A while back, I decided to try to refurbish a graphics card that had literally spent the winter outside (very corroded connectors, etc.etc.). When i foolishly inserted it into my daily use computer, nothing worked.

I pulled out the card, figuring it was dead. And inserted the previous working card. But to my horror, my stupidity and the refurbished card also appeared to me to have also killed off the motherboard, which afterwards only gave a beep-code of 3 long beeps.

(which later i tracked down to be Asus' "no display card detected")

The thing is, today, almost a year later; I replaced the motherboard with an identical one, only to have the same thing happen.

  1. I now know both the new motherboard and original graphics card both work perfectly. (And probably also the original motherboard as well)
  2. I'm writing this on on the very same PC and PSU, but using a non-aux powered Mini PCIe card
  3. So I'm thinking what might've happened is that only the PCIe power rail on the PSU is what got damaged.

So i'm wondering if anyone could tell me if, and how, i might be able to troubleshoot that (two 6pin PCIe rails) by using a (very basic) multimeter?. To verify whether or not it's actually the PSU that's partly 'blown'.

PCI-Express 6pin Aux power plug From https://www.tomshardware.co.uk/power-supply-specifications-atx-reference,review-32338-12.html

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  • \$\begingroup\$ Would it be as simple as putting the black probe into either pin 4 or pin 6, and the red probe into pin 1 and pin 3 (the yellow leads), while having the multimeter set at a range close to 12V ? forums.tomshardware.com/threads/… \$\endgroup\$ – DhP Jul 6 at 0:51
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Measure the voltage between a yellow lead (+12V) and black lead (GND). Yes, it's pretty much only that - black probe to black wire, red probe to yellow. Check each wire to make sure that they're all good.

That said, internal to the power supply, the groups of +12V tend to be tied together. It's unlikely that only one plug would be bad, but who knows?

Pin 5 has a special use. Its function is for the GPU card to detect that the power plug is connected, so it knows that it can exceed the 75W slot limit. The host plug only has this tied to GND.

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