Lightning damage! Couldn't track the fault, only that it appeared to be on the main board: part fried chip I think. I don't keep things any more as I tend towards hoarding and live in a small house with an unexpectedly enlarged family. I found similar main boards from differently labelled TVs but all with subtly different layouts (and codes) and prices just too large (for me) to warrant giving it a go.
Bad caps, I feel like Dr House trying to find Lupus, it's always suggested but never appears ... waiting for that one time to show up.
The whole board was trashed? The PSU on my previous TV failed (due to capacitor plague); I ordered a complete part replacement kit from eBay for like 10 bucks and swapped the bad caps using a wood burner as a soldering iron.
Did you check for broken/for parts listings for the same TV? At 4 years old, I'd expect a lot of 2nd-hand supply.