AX Series: make custom wires

Hey guys,

I've already posted this in the language specific part of the forum, but noone ever answered.

Hope you guys can help me out.

Here's the translation:

"

Hello dear community,

unfortunately the number of pins on the side of the AX series psus isn't the same as the number of pins on the other end of the cables (hardware-side).

E.g. the ATX cable of the AX650,750 and 850 has got 28 pins on the psu and 24 pins on the other side of the cable. -> there are double wired pins.

Now if you're going to custom sleeve the whole power supply, you're getting into big trouble there (especially if you want to do it heatshrink-free).

That leads me to my question: is it possible to make some custom wiring for the whole power supply, where you only occupy 24 of the 28 pins on the power supply unit itself? I basically want to have a "1 pin <-> 1 pin" layout.

Would the power supply then still meet the ATX specifications?

I'm aware that you won't recommend me to do that even if it's possible, because the devices aren't meant to work that way. Additionaly I could always go out and buy the sleeved cable sets of Corsair, but I don't want them for two reasons:

- I couldn't adjust the length myself

- I don't like the look of the heatshrinks

I hope that anyone could possibly help me out with that problem.

Thank you very much in advance.

Best regards,

Furion92

"

That leads me to my question: is it possible to make some custom wiring for the whole power supply, where you only occupy 24 of the 28 pins on the power supply unit itself? I basically want to have a "1 pin <-> 1 pin" layout.

Would the power supply then still meet the ATX specifications?

What do you mean by "can not be changed".

-> I surely can change it, but it will fail.

??

Or do you mean, it's physically not possible?

I mean, I can take the original psu connectors from the power supply and take some electrical wire and build it myself.

When I take a look at the pinout diagram of the AX750/850, I find the double wired pins to be the ones where the description says for example "GNDs" or "+5Vs"... What does "s" stand for and what's making those connections (-> the voltages/potentials) different from the ones without the "s"?

http://server.sgservicegroup.de/MassGate-Server/TECH-FACTS/CorsairAX-24Pin-Belegung/AX750-850-24-Pin-Belegung.jpg

I believe the 's' stands for Sense, which is a signal sent back to the PS that allows it to improve the voltage regulation of the 3.3V, 5V, and 12V rail.

Which brings up a question. If a 24 pin extension cable (which will not have the extra 's' wires) is plugged into the regular 24 pin cable supplied with the AX PS, does that mean the sense function is not working, since there is no feedback supplied to the PS? The answer is obviously yes, so the real question is, what is the affect of that on the PS?

Not including those wires in a custom cable like you want to do would do the same thing.

I think you miss the point that the ATX cable itself has always !24 pins on the mobo side (unless it's an old one with 20 pins)... So whether you crimp the two wires coming from the power supply together into 1 pin on the 24pin ATX connector and then connect it to the motherboard, or you extend the double-wired pin with an extension cable before connecting it doesn't make any difference.

However it would make a difference if I just wouldn't connect that one pin to ANY of the other ATX pins.

Now the question that's left is: what function have the sense connections and how would it affect the power supply if they weren't connected to anything?

I was wrong about the 24 pin extension cable causing the voltage sense function to not work at all, it will still work with an extension cable, but not as intended.

Instead of the voltage sense function sensing at the load itself (mother board connector) which is the intent, it will be sensing only up to the connection with the extension cable. So while the sensing circuitry will still be functioning, it will not be applying the appropriate correction.

Poorly designed power supplies will connect the voltage sense wire(s) at the same point as the voltage rail output wires inside the PS, not at the end connector, so they will not detect voltage fluctuations at the load itself.

The 3.3V sense line has been part of the ATX spec since at least the ATX 2.0 specification. I imagine that modular power supply designs in particular that want to have excellent voltage regulation have added the sense lines to the other rails, as we see here. I wouldn't be surprised if the two extra pins on an eight pin PCI-E connector are used as sense lines, as they don't supply power. I wonder why sense lines aren't used on the four and eight pin CPU/mother board power cables.

Alright, so these sense lines are there to compensate the voltage drop?

That means that removing those signals would let the power supply think that there isn't any voltage on the motherboard connector and it would either shut off or increase the voltage until it (or the components) dies?

-> the only option (not the best though) for me is to connect the voltage lines with the sense lines inside the psu... the voltage regulation wouldn't be as efficient as before, but I could indeed only use 24 cables for the main atx power connection.

Sadly, I'd have to open the unit -> void the warranty

Any other suggestions?

PS: I don't know why the 8 pin EPS doesn't have that sense connection... doesn't make SENSE to me :P

Regarding what would happen if the 3.3V sense line was removed (or no signal to the sense circuitry), I thought I read in one of the ATX spec documents, that is considered a fault condition and the PS should be shutdown, but I can't find that now.

The added sense lines on the 5V and 12V rails are not part of the ATX spec, so the result of removing the sense signal on those rails is uncertain. If that would cause the regulation circuitry to malfunction, then the PS probably would be designed to shut down if that happened. This level of detail is usually not available to the public, so finding it is difficult.

How about this for keeping the sense lines intact without opening the PS. You must use the 10 and 18 pin connectors on the PS, of course. If you can find where the three sense wires come back into the PS on the 10 and 18 pin connectors, how about using a short "jumper wire" from the sense output pin to the sense input pin?

The ATX spec for the 3.3V sense wire said it only needs to carry 10ma (10 milli-amps, or 0.010A) and suggests using a 20 gauge wire. These jumper wires would be between the 10 and 18 pin connectors on the outside of the PS. You would have the three additional short wires between the two connectors, so a little more messy than normal, but that's all.

Personally, I would prefer to use the sense wires as they were designed, but I think this would work if you wanted to eliminate them running all the way to the 24 pin connector.

Alright,

thank you parsec, this thread can now be closed.