It seems to be the on/off switch.

Linda_rhodes, It seems to be a problem with the INTERNAL switch-mode-power-supply and not the "ON/OFF" switch. You should have electronics technician investigate the SMPS to determine why it is going into shutdown mode. "Smart" smps's will go to shutdown mode when they detect a "fault condition" with itself or another electronic circuit. It does this to prevent a catastrophic, nonrecoverable failure from occuring!! e.g. sparks, smoke, fire. If unit covered by warranty, USE it first! Whenever posting a problem, always mention the date of manufacture from rear of set. Although plasma screen sets are different from "cold-cathode-fluorescent-lamp" back-lit screen tv's and computer lcd monitors, both require white light to see images on the screen. As a technician, the first place I would start looking for problem would be on the smps printed circuit board, to find cause of shutdown. Linda, I would also do search on web to see if other owners are having same type failure mode occuring for same or similar model!!! Have you been to YOUTUBE yet? Try there for video's of useful repair info also, even though you won't do the repair. Please post back to this response after doing some research. I'm 12fixlouie on fixya. Bye for now.