ACA power supply 19.5V, mystery third wire

[aspringv]

So I needed a new power supply for my old ACA build, and fished out this whopper from the Junk box. 19.5V at 11A? Sure! Should be fine.

On stripping the wire though, a mystery third, low gauge, wire was revealed...

This seems to have been connected to the +19.5 contact at the plug end. But on checking the PSU, it seems to sit at 18.2V potential.

Any ideas, what's it for?

 

[MAAC0]

I have disassembled a similar PSU before. From what I found on the Internet I Believe it's a identification wire of some sort in order to prevent other charges to work. On the Laptop in question, on the connector end the wire was floating inside the laptop.
Hacking a Dell power adapter — final (not really) | My Not-So-Boring Life

 

[aspringv]

Thanks!

The brick seems to work fine with it unattached and with no load... I guess the proof will be with a load on it.

 

[mpmarino]

I had a laptop (toshiba I think) where there was a center pin as normal. but the barrel portion had an inner and outer. The outer part of the barrel was 0v, and the inner part of the barrel was the same potential as the center pin.

From what I could tell, the battery charger power feed, and the laptop power feed were two separate circuits.

 

[mt490]

It's a signal wire for the connected device to identify it. Typically a 1-wire memory device is connected at the other end that stores information about the power supply.

The power supplies typically don't do anything, but eventually if it ever comes a day where we need to use USB-PD supplies (at 20V 5A) our lives might get a bit more complicated.

 

[aspringv]

Thanks for the answers everyone!

 

[aspringv]

...And definitely works fine. I accidentally left it on for a whole day... Stress test (accidentally) achieved and all good!