Hello, U3 power transistor gets too hot to touch a few seconds after turning on dac. U4 is OK. This problem appears and then disappears mysteriously, meaning the U3 transistor begins to work properly again and is not too hot to touch. This problem has appeared and then disappeared at least 12 times. Also, the blue power LED won't light when U3 is hot. I am very curious as to what the problem might be and would appreciate if you would advise me on this matter. I have had the unit for a little more than a year now and have been experiencing this problem for about 10 months. My TA10.1 power LED worked only for the first month after purchase. I've had the amp for a little over a year as well. Aside from these issues, I LOVE THESE COMPONENTS.