0.5 amp drain on the radio circuit

I have a 0.5 amp drain somewhere in the radio circuit these are the tests I have done
bench tested the radio 0.012 amps after power was hooked up and the radio was turned on the off.
Tested the radio circuit in the car with my meter replacing the radio fuse in the car
with radio in engine turned on the off and retained accessory power turned off I get just over 0.5 amps
same test with the radio completely disconnected and I still get just over 0.5 amps
with these tests I have determined that the aftermarket radio is not causing the problem so I need to know what else is hooked up to the radio fuse in my car