Computer power supply cables... why can't you just use any of cable?

Thread Starter

photonfanatic

Joined Nov 9, 2017
7
I have a modular computer power supply, and I needed an additional cable to run and additional card. Well I didn't have an extra cable, but what I did have is an older power supply that seemed to have the same connectors. So I plugged it in, and lo and behold it worked fine. But after doing some reading, it seems that people generally say this is a mistake. They say that it could fry components if you don't use a cable that came with the power supply or one you bought from the OEM. What I'd like to do, is understand why. I'm something of a newb when it comes to electricity. But to my mind, if the cable fits, it should work just fine.

You've got a connector, pins, and wires that connect to those pins. That's it. How can this result in frying anything? To me the only possible way, would be if you plugged it into the wrong port on the PSU. Since the ports on the PSU may be different, you might plug in a cable that does fit into the port, into the wrong port. And thus, supply too much power to the device. The only problem with that is, many power supplies are labeled. They'll tell you which ports are meant to power what. Its often printed right there on the power supply next to the ports. So if you had a cable from another PSU that fits, and you saw that it plugs into the port for a graphics card on the PSU, what could be the harm in that?
 

dl324

Joined Mar 30, 2015
11,506
Welcome to AAC!
I plugged it in, and lo and behold it worked fine.
A picture would be helpful so we can be sure of what you're talking about. In general, if the connectors fit, you just need to worry about wire size and length.
But after doing some reading, it seems that people generally say this is a mistake. They say that it could fry components if you don't use a cable that came with the power supply or one you bought from the OEM.
They might not know what they're talking about...
 

spinnaker

Joined Oct 29, 2009
7,835
I have a modular computer power supply, and I needed an additional cable to run and additional card. Well I didn't have an extra cable, but what I did have is an older power supply that seemed to have the same connectors. So I plugged it in, and lo and behold it worked fine. But after doing some reading, it seems that people generally say this is a mistake. They say that it could fry components if you don't use a cable that came with the power supply or one you bought from the OEM. What I'd like to do, is understand why. I'm something of a newb when it comes to electricity. But to my mind, if the cable fits, it should work just fine.

You've got a connector, pins, and wires that connect to those pins. That's it. How can this result in frying anything? To me the only possible way, would be if you plugged it into the wrong port on the PSU. Since the ports on the PSU may be different, you might plug in a cable that does fit into the port, into the wrong port. And thus, supply too much power to the device. The only problem with that is, many power supplies are labeled. They'll tell you which ports are meant to power what. Its often printed right there on the power supply next to the ports. So if you had a cable from another PSU that fits, and you saw that it plugs into the port for a graphics card on the PSU, what could be the harm in that?

Yikes! Is there a question in there somewhere?:eek:
 

#12

Joined Nov 30, 2010
18,210
At low frequencies, any wire with enough diameter and enough length, connected to the right place...will work.
Mistakes happen when one or more wires are not at the right place, like when there is a cross-over inside the cable where you can't see it. If you can see all the wires, all the way, there is no reason for a problem.
 

Reloadron

Joined Jan 15, 2015
5,646
Over the years as the personal computer evolved the supporting power supplies also evolved. More lines were added to the PSU including power for PCI-E and additional power for the CPU on the motherboards. Years ago using Dell as an example the 20 pin main motherboard connector (predating the later 24 pin version) was not standard to the ATX Form Factor drawings so using a standard ATX Power supply would cook a Dell Motherboard, even the traditional color codes were not the same. Dell called it "propitiatory" but most called it a ripoff.

Unless you can name the connector you are talking about such as PCI-E I am not sure what you are asking? Also per #12 above are you asking about wire gauge for ampacity?

The wire color code scheme is pretty standard but not always.

Ron
 

Thread Starter

photonfanatic

Joined Nov 9, 2017
7
Looks like there are just too many variables to risk it. I can't believe a simple wire would be cause for so much concern. As for wire gauge for ampacity, I can't be sure. I would think that the wires would be close enough to the correct gauge, since we're only talking about devices that are what... a couple hundred watts at most? Anyway I think I've seen enough now to conclude that I should just buy the cables from the oem. Still seems like it should be fine though.

So maybe... if you had a cable that would fit into a different PSU, it just might fit into a port that supplies too much power? And you're now running too much power to a device that was never intended to accept that much. That really is the only thing I can think of that could "fry something" as people seem to like to say. Cause if it wasn't supplying enough power, then the device just simply wouldn't work, right? Power being too low wouldn't actually hurt anything would it?

Yikes! Is there a question in there somewhere?:eek:
Yes at the top of the second paragraph, also at the bottom of the second paragraph. Did you read it?
 
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spinnaker

Joined Oct 29, 2009
7,835
Looks like there are just too many variables to risk it. I can't believe a simple wire would be cause for so much concern. As for wire gauge for ampacity, I can't be sure. I would think that the wires would be close enough to the correct gauge, since we're only talking about devices that are what... a couple hundred watts at most? Anyway I think I've seen enough now to conclude that I should just buy the cables from the oem. Still seems like it should be fine though.

So maybe... if you had a cable that would fit into a different PSU, it just might fit into a port that supplies too much power? And you're now running too much power to a device that was never intended to accept that much. That really is the only thing I can think of that could "fry something" as people seem to like to say. Cause if it wasn't supplying enough power, then the device just simply wouldn't work, right? Power being too low wouldn't actually hurt anything would it?



Yes at the top of the second paragraph, also at the bottom of the second paragraph. Did you read it?
No I would rather read novels. ;)
 

kubeek

Joined Sep 20, 2005
5,732
From what i see connectors on modular power supplies are not standardized and I wouldnt risk swapping them even between different models of the same manufacturer unless i measured the voltages first.
 

Thread Starter

photonfanatic

Joined Nov 9, 2017
7
Just so I'm 100% clear on this, what would be the whole procedure? I'm imagining just measuring the voltage at the psu, on psu #1. Then just going over to psu #2, and measuring the voltage there too. If its the same voltage, I'm good to go. On each individual pin, where I'll be connecting the cable.
 

spinnaker

Joined Oct 29, 2009
7,835
Just so I'm 100% clear on this, what would be the whole procedure? I'm imagining just measuring the voltage at the psu, on psu #1. Then just going over to psu #2, and measuring the voltage there too. If its the same voltage, I'm good to go. On each individual pin, where I'll be connecting the cable.

In addition you can verify the voltages at the end of the connectors by looking online. The ends that plug into the system board and drives are standard connections. There are many resources online where you will find connection information.
 

Thread Starter

photonfanatic

Joined Nov 9, 2017
7
In addition you can verify the voltages at the end of the connectors by looking online. The ends that plug into the system board and drives are standard connections.
So it would be something like this:

Measure the voltages at on each pin, in both PSU's. Then, plug the cable into PSU1, and measure the voltages. Then, plug the cable into PSU 2, and measure the voltages. Record all results and compare, if the same, then I'm good to go and nothing bad can happen.

But what about amps?
 

tcmtech

Joined Nov 4, 2013
2,867
So it would be something like this:

Measure the voltages at on each pin, in both PSU's. Then, plug the cable into PSU1, and measure the voltages. Then, plug the cable into PSU 2, and measure the voltages. Record all results and compare, if the same, then I'm good to go and nothing bad can happen.

But what about amps?
Yes that would be correct.

Amp draw is dictated by the load attached to it so as long as all the combined loads do not exceed teh amp rating ether the power supply or the individual connectors you likely won't have any problems.

Like you, I've had to add more wiring and connectors to computer power supplies before to accommodate additional gear on older computers where buying a new power supply was not cost justifiable just because it had 1 - 2 more connectors or connectors of a newer design that the older supply did not have.

Hard drive, graphics card, and or fan add ons were the most common problem where I ran in to your same situation.
 
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spinnaker

Joined Oct 29, 2009
7,835
But what about amps?
You are not going to know that for sure till everything is powered up. Just inspect the wires and see how they compare in diameter as well as materials . Used. If they are close then you are likely good.

If the replacement has thicker conductors then you are good.
 

Thread Starter

photonfanatic

Joined Nov 9, 2017
7
You are not going to know that for sure till everything is powered up.
Yeah, about that... lol. I did that at the very beginning before I created this thread, and it all fired right up and worked fine. Even played demanding games on it, delivering a load to the video card. (gtx 1070)

The cables fit and I assumed everything was just standardized. They looked the exact same, and they fit, and the PSU's are nearly 9 years apart. Must be some kind of standard, right?

Apparently there isn't any standard and I was only sheer luck that my cables fit and worked, and didn't fry anything. Or is it? Seems like there must be something I'm missing here. Perhaps its like this: Most of the time, you'll be fine. But there is a small percentage chance that you will not be fine, and you will fry your components. Which has happened to people, so it made the rounds on the internet and now everyone says "Don't do it". Perhaps its something along those lines. So you should always check.

Anyway thanks to everyone in this thread, your help is much appreciated.
 
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