[SOLVED] Identify power rails with a multimeter

[leonsk29]

How can I identify the individual 12V power rails of a PSU with a multimeter? I read somewhere that you can do this my measuring resistance between the different 12V lines on the different connectors, but I have a PSU which says it has two 12V rails, and every time I measure resistance between every yellow cable the multimeter beeps and displays "0". Does that mean that the PSU really has a single 12V rail ? Please help. Thanks in advance.

PD: the PSU doesn't identify the individual rails by cable color nor its documentation.

PSU: Seasonic SS-350ET.

 

[refillable]

What are you going to do with the SS-350ET? Why do you need to know the rails?

I think the fact that it shows "0" is because that every PSU (with the exception of big, old ones) does not have 12V split into actual rails. They are only divided by their protection channels and that's why it's very hard to know which rail is which.

 

[DSzymborski]

As refillable notes, it's not actually a "true" multi-rail PSU. It was designed this way because there used to be a 240VA limit (20A) under ATX spec. You can see this because the PSU itself says it conforms to ATX 2.2 spec from 2005.

I hope this isn't a PSU you plan on pushing or anything. This was a fine PSU for light systems, but it's not 2020. The fact that it doesn't meet the 2007 ATX revision should be a big clue as to just how ancient this is by this point. And since it was for light purposes, they didn't use particularly good capacitors or anything.

 

[leonsk29]

As refillable notes, it's not actually a "true" multi-rail PSU. It was designed this way because there used to be a 240VA limit (20A) under ATX spec. You can see this because the PSU itself says it conforms to ATX 2.2 spec from 2005.

I hope this isn't a PSU you plan on pushing or anything. This was a fine PSU for light systems, but it's not 2020. The fact that it doesn't meet the 2007 ATX revision should be a big clue as to just how ancient this is by this point. And since it was for light purposes, they didn't use particularly good capacitors or anything.

Don't worry, it isn't powering any 2020 components either. And I have no problems with it, I just wanted to know the rail distribution and if it can be found using a multimeter measuring resistance like some people say.

 

[leonsk29]

As refillable notes, it's not actually a "true" multi-rail PSU. It was designed this way because there used to be a 240VA limit (20A) under ATX spec. You can see this because the PSU itself says it conforms to ATX 2.2 spec from 2005.

I hope this isn't a PSU you plan on pushing or anything. This was a fine PSU for light systems, but it's not 2020. The fact that it doesn't meet the 2007 ATX revision should be a big clue as to just how ancient this is by this point. And since it was for light purposes, they didn't use particularly good capacitors or anything.

I don't plan to push it or anything, and it isn't powering any state-of-the-art components, I just want to know if the rails can be identified with the resistance measuring like some people say.

 

[DSzymborski]

Don't worry, it isn't powering any 2020 components either. And I have no problems with it, I just wanted to know the rail distribution and if it can be found using a multimeter measuring resistance like some people say.

Just making sure! You wouldn't believe what some people do. Just this week we had a guy who asked a seemingly innocent question about semi-passive fans in PSUs and it turned out he was asking because he wanted to know if his PSU needed a fan because he wanted to take the fan out of the PSU and connect it to a light switch.

 

[USAFRet]

Just making sure! You wouldn't believe what some people do. Just this week we had a guy who asked a seemingly innocent question about semi-passive fans in PSUs and it turned out he was asking because he wanted to know if his PSU needed a fan because he wanted to take the fan out of the PSU and connect it to a light switch.

Or the guys wanting to power a car stereo, in their bedroom, from a computer PSU.
Hey, power is power, right?