Is it safe, or maybe I should I say "logical", to take an AC adaptor and splice the wires, reconnect them and solder together with a USB cable to power a device?
I had an old gameboy advance sp laying around and had an idea (sometimes my ideas are good, but most of the time they are not so good), well I cut the ac adaptor wire about half way and then took a usb cable, cut it and then soldered the wires together. Not knowing which wires should be connected to the corresponding wire, I took a guess and matched most of the color coded wires together. There were some that didn't match up so I just guessed and prayed.
The original plan was to be able to use it as a transfer cable, but like I said sometimes my ideas aren't so good. It turned out, it actually charged the gameboy. To my surprise, nothing bad happened, it charged the gameboy just fine, no smoke came out from anything, no sparks either. But that brings me back to my original question; is it safe? Would the watts or amperage be an issue with the original charger being 100V-120V?