Panasonic Stereo Trouble

In my 1990 Nissan D21 Pickup, the Panasonic stereo model: CQ-RX200U stopped turning on. All fuses are intact. When I test for power getting to the radio through the battery lead and power lead, there is enough power (~11v) getting to the stereo w/o it connected but after plugging the stereo in the battery lead only gives 1v. Why is this happening and how do I fix it?