Hello, the mosfet when they get short have the bad habit of taking the components they have in the gatr, both the resistors, transistor diodes and the IC driver even, it would not hurt to combine the tl431 and the opto, also check that no there are shorts in the secondary as bad electrolytic
I leave the diagram for you to study from a safe download from I repair
https://www.yoreparo.com/tv/televisores/lcd/led/manuales/5925543/noblex-24lc827h-chassis-ue7m
luck and regards
Tobias Tv MDQ