1A is enough for "modern" 3.5" drives, I don't know about 5 1/4, DD or really old drives

Thanks! That helps me a lot!

Most modernish drives also need only 5V. And modern ones need really only 500mA.

OK. Then I can look for a power supply of 5V AC.
But apparently that's not as common as 5V DC.
Thanks!

Wow wow, no AC!!!! Only DC!

Oh! That would be a huge mistake ...
THANKS!

Where did you get to that conclusion, that you need AC current? Almost everything that is low voltage is DC.

Bear in mind that the current supply of the power supply you're going to use can greatly exceed the needs of the device being powered. If you get a 2 Amp supply that puts out the correct voltage in the polarity you need, you're more than safe in most cases. You only risk letting the magic smoke out if the supply you use is at, or below the equipment's current draw, because that's basically overcrowding the power supply.
As far as AC and DC go, you almost never use AC. In the case of the Nintendo Entertainment System, its adapter puts out 10V AC, but only because the NES itself has a bridge rectifier inside it that converts it to DC.

Mister Xiado wrote on 2020-12-03, 11:15:

Bear in mind that the current supply of the power supply you're going to use can greatly exceed the needs of the device being powered. If you get a 2 Amp supply that puts out the correct voltage in the polarity you need, you're more than safe in most cases. You only risk letting the magic smoke out if the supply you use is at, or below the equipment's current draw, because that's basically overcrowding the power supply.
As far as AC and DC go, you almost never use AC. In the case of the Nintendo Entertainment System, its adapter puts out 10V AC, but only because the NES itself has a bridge rectifier inside it that converts it to DC.

So the NES power supply is basically a step down transformer? Why would they do that?

drosse1meyer wrote on 2020-12-03, 13:11:

So the NES power supply is basically a step down transformer? Why would they do that?

Yes, if you open an original NES AC adapter you can see that it is just a transformer. As Mister Xiado says, the rectifier and smoothing cap is in the little RF modulator metal box on the side of the console. From there the 7805 attached to the metal box is fed in order to generate the regulated 5V for the main PCB.

drosse1meyer wrote on 2020-12-03, 13:11:

Why would they do that?

Perhaps to fry people's Sega Master System/Genesis systems when they used the NES power brick with it? Or maybe it was cheaper for some reason.

Reality, cheaper and easier, even more practical. Because transformers heat, and it it not so good for other electronics. And a good quality transformer is robust and almost has infinite lifetime.

I wanted to use an adapter with output 5V 5A. I thought it would do.
And why I assumed 5v ac: the properties of the drive I wanted to use I saw : 5V, without further indication.
But that was a bad interpretation...