Battery drain on 98 Chevy z71.

Battery drain on 98 Chevy z71. Disconnected alternator and pulled all fuses one at a time with test light connected in line with positive post of battery, and test light remains lite. The only one that makes it go off is the fuse under the hood that is marked BATT it is a 50 amp fuse. Where would I start looking for a short with this fuse?