Dead Tablet - won't Boot

After leaving my device on the original charger overnight, the following morning my Samsung Galaxy Note 10.1 would not boot. The charger tests good and still charges my wife's tablet. Holding the power button down for 30 seconds, holding the power and volume buttons down for 30 seconds, and trying these combinations while touching/tapping the screen all have no effect. I opened the unit and unplugged the lithium battery for a minute and then reconnected it - still nothing. Does anyone have any suggestions before I ship this unit back for repair?