I have 2 Ultras, bought them 2nd hand years ago, so I decided to change the batteries. To avoid having to restore all my presets etc I did it while they were on. Piece of cake. Just dont wear nylon sox or clothes, touch the chassis, and don't stick your fingers in the power supply, or touch any of the components with your fingers. The hardest part is getting the top off the unit....some of those screws are really tight....stripped one and had to drill it out.