Panasonic th42pa20A

Tv won't turn on standby red light flashes and when TV is on it switches of and light flashes it then NOTHING and you hear another click and then the red light flashes again 12 blinks no picture or sound,replaced ps board,still 12 blinks any ideas?
I change the PS and still I'm having the same problem
Can anybody help me with the next step I have to take?
I download the service manual for this TV but it does not shows the problem