Hello and sorry you're having problems. Did this issue occur after a storm or power outage? Have you also tested any voltages on the power board with a meter yet?
thought I'd reply before I click your rating. [good]. I know where I am now and looked up price of power board, £35 ish.
not sure I shld take the back off ! it was a bit of an expt as a tv and I think I'll go for a better quality one in view of your advice.