Originally Posted by donv
I can tell you this about going the other way. I bought a Casio Keyboard at a yard sale for my grandaughter but it didn't have a power supply. I had an old one that was the right voltage, but the amperage was about 20% of what it required. After about an hour, it killed the keyboard. That was the verdict from the repair shop.
This is exactly true. I've built a couple of computers in my time and the power supplies you use tend to be more about power in Watts than current, same principle. You could fit a 1.5kw power supply to your bog standard beige box that you're using now (to give you an idea, most stock PCs that are not designed for performance or a small form factor come with 250-300w power supplies) and it would actually work better due to it being designed for performance+better cooling etc. However if you fit a power supply that is too low a current and you exceed that current then you actually do risk blowing components so yeah this is absolutely true.
Another interesting fact is that if you exceed the rated electricity for your plug sockets (in the UK it's 13A in other places it might be different) then the whole thing will set on fire! That's what fuses are for, although i'm sure you knew that already! That's another example of only drawing the current it needs right there. your plug sockets are rated for 13A but that's a huge amount of current that very few devices would ever need, how would they work if this wasn't true?
In short TS if you got bored, don't worry about the current output being too high, in fact make sure your power supply can give you a HIGHER current then you'll need!