I wish I would have wrote the model down posterity, but at one point I worked a trading company and a number of the users had ISDN at home. There were two 'different' modems, and I say different because only the model number on them notified you of it.
One had a plug that output DC power. One had a plug that output AC power.
They were the same size wall wart. Same size barrel. But if you plugged the AC adapter in to the DC modem it would make a noise like you curled the modem up into a ball and let the magic smoke out.
The scenario you describe, where I'm looking for a power supply among a set of devices, to power another device, that is less likely to turn up a winner. But chances are non-zero enough that I do wander around looking for other options when a power supply is missing.
Really it should be a manufacture requirement that the barrel port on the device have a waterproof hard to destroy sticker, or case moulding that lists it's requirements. As the years have gone by I've seen way too many devices with a plug hole and no idea what it thirsts for, leading to deep searches on the net for the product. Also the wall warts themselves are commonly made by some other group, so once separated there is little to no visible pairing identification other than looking for output/input power on both devices.
A quick Amazon order, snip the wire off the old, splice it to the new and a little soldering/heatshrink later and we're back in business. Plug it in and... nothing. Turns out, the original power supply had it's polarity reversed. So then I opened the fridge and swapped the connections on the backside of the socket because it was less fuck-about than re-splicing the wire. Fortunately a few confused minutes of reversed polarity didn't damage anything (not that there's really anything to damage, it's a peltier plate and a fan)
Genuinely, why? The standards make things easier. Why go out of your way to not use them?
Doesn't that make it a heater, instead of doing nothing?
Probably the best connector we've got for things that need it, but I'm glad we have USB-PD power now
When you see a barrel connector all the following things are true:
1) no voltage can be inferred
2) no amperage can be inferred
3) Not even the polarity can be inferred
You must check the device and the wart for all that information.
Oh, man, that reminds me of how I found out that MicroLogix PLCs[0] come in AC flavors and DC flavors. So the MicroLogix 1400 I had lying around here used an AC adapter, and you screwed the stripped wires into the holes that used screw retainers. Easy-peasy, just make sure the adapter's not plugged in in you wire it up. The boss orders me another MicroLogix 1400 for long-forgotten reasons, and to get it bootstrapped, I decided to use the adapter from the other 1400.
I already gave away the plot in the first sentence, and you can guess what happened next.
[0] https://en.wikipedia.org/wiki/Programmable_logic_controller
