My LG LED TV 42LB5610 goes on and off along with its sound

My LG LED TV 42LB5610 goes on and off along with its sound

My LG LED TV 42LB5610 goes on and off along with its sound every few seconds. I tried changing the motherboard of the TV set, changed the HDMI cable but ultimately it doesn't make any difference. The problem still persists.

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