Brown burn marks on the board would indicate a problem area that should be checked.
This would be a whole lot easier if you can Google your TV make and model number, and
see if you can find a free schematic of your TV.
You read 320VDC, so I assume you have a VOM (Volt Ohm Meter) (Also sometimes called a DMM, Digital Multi-Meter)
My initial thought concerning your problem is a big electrolytic cap (or capacitors), or an open-circuit power semiconductor.
It could be anything with the information you've supplied so far. Hope you have the patience to troubleshoot this (which may take a while).
So you'll be disappointed if you expect this to be a quick repair.
We can listen to your symptoms, and offer advice on which component or circuit area to check next, until we isolate the problem.
We'll try to help if you've got the patience to work with us.