Power supply with positive and negative voltages 12 and 24v where to buy ?

Does it have to be switch mode?
You can always do that with two power supplies but leave one not grounded, ground the one with the minus side used as the 0.

How much current do you need on the -12? Perhaps an isolated DC-DC converte connected to the 24V main supply would work?

My mill has just one big 24V supply and then a bunch of DC-Converters for the other voltages:

photos.app.goo.gl/EqX6ExZZ1fR2yzEM7

To get -12V you would need to connect input negative to output positive. I don't know how much they like that, in general.
(I just checked my drawer and found that all three types I have use a common GND, so won't work)

However, ebay has lots of +/- 12V step-down converters, and you can always ignore the +12.

Every PC power supply should have a -12V, it is used for audio.

smc.collins wrote:

many many many new PSU's do not have the -12v rail

They do, is this new enough:
www.google.com/search?q=asus+rog+thor+12...ges&aqs=heirloom-srp..
It is an ATX standard, so till they move to the new 12V only standard, they will have -12V.

Reading this back it came to my attention i never mentioned that -12V rail on PC power supplies is very low current, usually 0.2 to 0.3A.
Sorry for the omission.
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I think i still have some very old AT power supplies, the ones with a mechanical toggling switch, pretty sure they also have -12V, but i would not bet on it.
Also have anything in between till the one i linked above and some more of those monstrosities, thinking of using two of those 1200W for welding, or 10 of them for plasma cutting!
At the very least, they are much, much more efficient, but expensive.