'89 battery

Hey, I have an '89 Range Rover and lately the battery drains everytime I leave the engine off for a while. I heard of the CD changer problem so I cut the main wire and removed the fuse, but that didn't help.
Does anybody know if there was something I missed or if there is another reason it might be acting up?

Also, I'm not very automotive savvy and can't find the fuse box for the life of me. I was going to check all the fuses. Any help?