Help with Corsair AX860i to ASUS P9X79 LE

Kagetora

Honorable
May 16, 2013
25
0
10,530
Ugh. I need some help, because apparently I'm too stupid for this anymore. I am trying to get my 24-pin connector on my Corsair AX860i to power my ASUS P9X79 LE motherboard. I am having trouble figuring out pin 17.

A bit of background: the cables that come with the PSU are WAY to long, and drag all over on the CPU cooler and such, so I built a cable, cannibalizing the 14+10 pin Corsair PSU connector in the process. The cables been wrung out three times, and I copied the original cable pin-for-pin as I constructed the new one (removing a pin from the Corsair connector, wringing it out to the other end, then matching that wire from the new connector). The cable is right.

So, the problem. The Corsair cable ties pin 17 on the PSU (3.28V according to my DMM) to pin 24 on both the PSU and mobo (3.29V). Should be no problem. Pin 17 on the mobo is listed in the manual as "-5V," but more modern schematics list it as "NC" and that pin is empty on the mobo connector, that wire being doubled up with pin 24.

When I plug this cable into my PSU, and hit the self test button, I hear a click and the PSU won't power up. If, however, I remove pin 17 from the PSU connector (which is doubled to pin 24 at the other end), it self-tests fine, green light, fan whirring, gtg.

The original cable had (and still has, because I left the mobo connector on it when I cannibalized the PSU connector) the exact same connection, i.e. 17/24 PSU to 24 mobo. I didn't try self-testing the PSU with that one plugged in, but its the same connection.

What the hell am I doing wrong? Whats going on? Any help or insight would be appreciated. Thanks in advance.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Sure...there just isn't room in my case. I'm re-using an old case I customized some years ago, and the area around the PSU up at the top is super-cramped. Adding 2 feet of inflexible cable up there when I really only needed less than half that seemed like a bad option, when I have a ton of other cables running up there too. Plus, as I mentioned, the cable is heavy, and was trying to ride on the CPU heatsink/cooler (which seems a bit on the large size, but, hey...I guess thats how they make 'em these days.)

The other question is, why does it matter? The cables are identical except for length...
 

clutchc

Titan
Ambassador


Apparently not. The 20+4 connector/cable must not be internally wired the same as is the 14+10 cable. What make/model PSU did it come from?
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Hmmm. Let me explain better. My first post may have rambled a bit. I bought 22 pre-sleeved wires with the connectors in place, and another 2 of a longer length. Female-to-female, as the PSU and mobo require (and as the original cable is). I also bought a 24-pin connector. Then I put all 22 wires in the new connector, and took the two longer wires, cut them to length, ran them to a single connector, and put them in pin 24. Now, this connector, which goes to the mobo, is identical to the one that is on the original cable.

Then, one by one, I removed wires from the 14+10 pin Corsair connector, wrung it to the original mobo connector, then inserted the new wire/connector from the new mobo plug into it, duplicating the original cable one wire at a time. The doubled-up wires go to 17 and 24 on the PSU connector, just as they did on the original.

It really is an identical cable. There is no internal wiring on the 14+10...its just two plastic connectors, like a 20+4, only split at a different point. As I said, its been wrung out multiple times, and the PSU self-checks fine as long as I remove the pin 17 wire from the PSU connector. Its bizarre, as both pin 17 and 24 on the PSU DMM at 3.2x volts. Apparently I'm missing something or stupid.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Ugh. According to that diagram, I am talking about pins 13 and 20. NC and +3.3V. The 5th one up on the side with the plug retention rocker, and the one at the far end from that. And all the wires were black on the Corsair cable...not much help there.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Sorry. The pin guide in the ASUS manual only labels pin 1, and I thought it went up to 12, then crossed over to 13, not went back to the other end to start at 13. Thats where I got the 17 and 24 from. Its 13 and 20.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Ok, I just took the DMM and checked every single pin on the connector, according to the Wiki link diagram. Everything is correct...each 3.3 is 3.29, each 5 is 5.0, each 12 is 12.01, each COM is 0. The PWR_ON was 4.96V, the PS_ON was 4.50V. The cable is right...right up until I insert pin 20 back into the PSU connector. Then it stops working.

To clarify from my early "wrong pin number screw up," pins 13 and 20 on the PSU connector run to pin 13 on the mobo connector, just as the original Corsair cable did. They should both be +3.3V, but when I have 20 plugged in to the PSU connector, it fails self-test. Works fine with that pin out.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
I'm starting to wonder if I shouldn't just run 13 to 13 and leave 20 empty on both connectors. After all, its NC on the mobo, and there shouldn't be any need to double-up the 13 on the mobo to two 3.3V rails.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Hmmm...according to the Wiki article, 20 on the PSU is supposed to be "3.3V Sense." With the DMM, my PSU pin 20 is actually reading 3.28V, measured from the bare pin itself to case ground. Not sure if that is correct or not.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Right. I'm just wondering why I have 3.28V on the 3.3V Sense pin when measured from pin to ground. Is there actually supposed to be a voltage there, if it's just "sensing" the other 3.3V outputs? Could I just leave this wire disconnected entirely?
 

clutchc

Titan
Ambassador
Yes, there is actually voltage there the same way there's voltage at your voltmeter's probes when you test, even thought the voltage at the voltmeter does no useful work.
The pin marked NC should be left empty. No wire. Or at least not connected between PSU and MB.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Right. I got that pin 20 on the mobo is empty, "NC." Can I also leave pin 20 on the PSU, i.e. the 3.3V Sense rail, empty? Why does the PSU self-test fine if this pin is disconnected, but fail if it is connected? With the mobo connector plug just hanging in the air, unconnected? Am I missing something?
 

clutchc

Titan
Ambassador
I would leave the terminals for pin 20 wireless/pinless. Pin 13 would normally have 2 wires on it at the MB connector end; the 'real' 3.3V wire (org) and the 'remote sensing' 3.3V wire (brn). But I don't know how it connects inside the power supply itself. Does the original modular cable have 2 wires on pin 13 at both ends' connectors?

Since you are working with a modular connector with a plug on each end, I can't really help you there. But you seem to already know what works and what doesn't.
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
No, the original cable has the wires running from 13 and 20 on the PSU connector to 13 on the mobo connector. Both wires run into the same pin on 13 mobo. The 3.3V Sense wire is thinner, since supposedly it doesn't carry current.
 
G

Guest

Guest
I am having the exact same problem with the Gigabyte Z87X-OC. It will just not power up and I have the same issues with the clicking and green Light!
 
G

Guest

Guest
I am having the exact same problem with the Gigabyte Z87X-OC. It will just not power up and I have the same issues with the clicking and green Light!
 
G

Guest

Guest
I am having the exact same problem with the Gigabyte Z87X-OC. It will just not power up and I have the same issues with the clicking and green Light!
 

Kagetora

Honorable
May 16, 2013
25
0
10,530
Yeah, I don't think it is/was the PSU. Here's the saga:

So, the motherboard wouldn't even TRY to power up. Even if I shorted the PWR_ON pins on the board directly. Nothing...a brick. So I RMA's it back to Newegg, and started delving into the PSU, because I thought it was behaving oddly. I FINALLY managed to get someone alive on the line at Corsair, and he tested an 860i they had, and told me that it behaved differently than mine did, so I should probably RMA that as well. So I did.

When I got the mobo and PSU back, the PSU behaved EXACTLY like the one I had sent back...so I don't think there was anything actually wrong with it. I think the guy at Corsair just didn't actually understand what I was telling him to test. It was a real struggle on the phone with him, and I'm pretty sure we were not on the same page.

Anyway, I put the system back together bare-bones...just PSU, mobo, CPU, and 2 sticks of RAM. And it booted up fine! Woo hoo! Gave me two error LED's, of course...no VGA device or Boot Devices installed, which I expected because I hadn't plugged them in yet. So I did, and booted up again.

Still got the VGA error, and no output from the EVGA GeForce at all. Grabbed an old video card and installed it instead, worked fine. So I had to RMA the GPU back to Newegg as well. This is getting ridiculous.

But, at least the computer is working now, right? Even if I have to wait for the new GPU to show up so I can replace the old one I put in there? Wrong. So, I'm thinking I will load the OS, get all the updates done, get everything ready to go, so all I have to do is swap GPU's and fly. Now the BIOS can't find a hard drive anywhere...it doesn't recognize the Seagate 1TB I installed. ARE YOU KIDDING ME? So, I grab an old 80GB blank drive I had lying around, and it recognizes that FINE. At this point I am so pissed I drive over to Best Buy and just buy a new hard drive. It recognizes that one fine too...so I go ahead with my OS install, and have to RMA the original drive back to Newegg.

So, out of 6 major components (CPU, mobo, GPU, RAM, PSU, HD), FOUR OF THEM came to me DOA. F-ing ridiculous. Although I don't think there was anything actually wrong with the PSU...the guy at Corsair just wasn't very sharp.

Its all done, up and running now...almost 2 months after the first box from Newegg arrived. This is the last computer I build. For an extra $200, I could have had the EXACT same components put in a case and shipped to me from IBuyPower or CyberPowerPC. I know. I checked. I won't do this again, and I won't be ordering from Newegg again. Their RMA policies, where *I* had to pay to ship bad parts back, is ridiculous, and glacially slow. Eventually I complained enough that the GPU and HD were shipped back on THEIR dime, but I still had to pay for the mobo and PSU, and lost an incredible amount of time. Worthless.

In any event, I don't think it was the PSU, and yours is probably ok as well. As long as it passes Self-Test when you plug it into the wall and press the button (with nothing attached), it's most likely fine.