This morning I went to hit with my tennistutor. I've had the tennistutor for about 7 years now, and haven't had any problems with it. But, this morning after hitting with for only 30 minutes, it suddenly stopped functioning. I called sportstutor, maker of tennistutor, and suggested to bring the unit to thier facility. Sportstutor is only 15 minutes away from me, in beautiful, sunny Burbank, CA I arrived, and spoke with James. He checked out the unit, and diagnoised that the curcuit board panel had gone bad. He installed a new board, and I asked how much do I owe? He smiled and said "don't worry about it". Wow!!!! How is that?? Not too many companies would do that. Thanks sportstutor!!! I highly recommend tennistutor indeed.