I'm having the same issue. I have been powering it off of a 5v 2.5amp wall charger and it has issues staying on for longer than 30 minutes. I have tried using a plain usb to computer to power it with no better results. A weird thing that happens to mine is the switch does nothing after the 30 minutes. Switching it on and off does nothing; I have to un-plug then re-plug it in.
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RE: Power dock turning off after 30 minutes