Does the radio display alway iluminate?

I was looking for the right power supply to tap in to on the fuse panel of my `04 Ranger. I have completed my work and now notice that when the key is on that the display area is lit on the radio even when it is turned off, and with the headlights out. The main reason that I ask is that I fried a CB power cord in the process of hooking up this power supply multiplier. I crossed the pos & neg when hooking into the panel. Am I being paranoid? Can someone run and and see if there's is lit up all the time.