Hi;
I am Armadillo from a small country; Welcome;
Break down the power supply into section, switching, pfc, backlight and the incoming section.
Take out fuse FI801 to break switching from PFC, at the same time check if the fuse is blown,
take out D1810 [supplying to backlight].
and then you check for shorts by measuring ohms,
Suggestion;
First you unplug, verify uplug and discharge all capacitors.
QP801 and QP802 and across Bridge rectifier BD801S Pin 1 and Pin 4; [PFC]
QM803 [Switching]
across CX803S; [Power incoming] and also cross Bridge rectifier BD801S Pin 2 and Pin 3
Q1813 to Q1816 [backlight]
identify the faulty section and troubleshoot from there.