I thought the unit was connected to a UPS, but it isn't. It's on a rather large surge protector that is behind our TV unit, so I thought it was a UPS. I don't own a voltmeter, but I will see if I can get my hands on one. Is there a list of problems that I can start to eliminate? I am pretty sure that it is not the hard drive. The rebooting continued after installation of a new hard drive. When the problem of rebooting started several months ago, I noticed that it happened a lot when we used NetFlix or Amazon. The unit would freeze or reboot. Then it started happening with TV shows, and has been rebooting more frequently. Now, we can't watch anything for more than a minute or two before it reboots.