R50 display garbles from AC to DC
 

Hello all,
I am new to this forum, so please bear with me.
I have an R50 that works well when it plugged in, but if I disconnect the ac power, within 15 seconds the screen goes into vertical lines, then horizontal lines, then the system freezes. To resolve, I must hold the power button until unit shuts down, plug it in again, and then power up.
Any thoughts would be appreciated, thank you.