Pioneer deh 236 install guide - Car Audio & Video

I got one of these off my sister, but i didnt have a plug for the back. cutting up an old atx psu plug does the job, but then i had to find which wires did what, so i took it all apart and looked at the bottom of the circuit board, the plug has 12pins, 4 on each side are for speakers and the center ones are Acc, Bup (back up? constant power), Gnd, B. Rem (amp/auto antena remote)
i connected the gnd to negative of a power supply, and on connecting the bup to positive,, it seems to just short the powersuply.
i dont see what went wrong.