49uf680v flashing 3 times

[dynomoman]

Got an LG 49uf680v that's flashing 3 times. Power supply fault or mainboard?  Set runs approx. 5 minutes then I see verticle white lines on picture then set goes off. Standby light flashes red 3 times. Set won't come back on for about 1 hour. Heat cold does not seem to affect fault.