I've got a cheap sony headunit that i'm trying to put in, when I plug in the power cord you can hear the cd player reacting and wanting to spit a cd out and such. But then when I go to turn the ignition to try it out to listen to cd's it dosn't show anything on the face plate. I found out that everytime I do this it blows the "ROOM" 7.5 fuse. I know that killing the fuse will not allow it to come on properly, but why is it killing the fuse everytime i turn the ignition over to try it out?

it's killing me, i need sound in my car

 

I believe the ROOM fuse should be a 10 and not 7.5?

 

on my fuse box cover it says "7.5 ROOM"