Samsung LE46M87BD Power cycling

[All Mod Cons]

Hi All,
I have a Samsung LE46M87BD. It powers on and works fine for about 5 minutes. Then it starts a cycle of powering off and powering back on again every 17 seconds.
I've checked the caps on the power board. They look ok but I replaced 2 x 2200uf 10v, 2 x 1000uf 25v and 1 x 1000uf 10v anyway.  Unfortunately after this I still have the same fault.

Could anyone please suggest what else could be wrong or a candidate for changing?
Thanks,