As a kid I played with batteries and wall bricks or wall warts or whatever you call them(transformers). I would not say you need an especially robust one. They come in different sizes based on the amount of voltage they output and the potential current they can supply. Basically if you are playing with a 9 volt battery and want to replace it with a transformer just look for one that says 9v DC output on it.
There are people who say things like its not the voltage that kills its the current but through the human body under normal conditions it takes a decent bit of voltage to induce enough current to really hurt you. Watch out for things with large capacitors and large voltages. If you want to take something like that a part let it sit for a long time for the capacitors to discharge. I worked at a TV repair shop in high school dismantling tube TVs for scrap components. The first step after opening was to use a large screwdriver to discharge the flyback transformer.
> Watch out for things with large capacitors and large voltages.
Oh man I have some retrocomputing equipment I really want to play with but I'm a little worried as there's a huge capacitor, some of the wires coming off the power supply manual are visibly old and to add to it, one of the first pages in the maintenance manual is a CPR guide.
I would not say you need an especially robust one. They come in different sizes based on the amount of voltage they output and the potential current they can supply.
They're also typically really cheap, which can be an advantage if you fry one. Or two. Or ten. Not that I'm speaking from experience or anything. :-)
Seriously though, if you have any kind of thrift store, surplus store, or something of that nature near you, you can often pick up random wall warts for next to nothing.
