I will try to assist you with this question.
The pop you heard was probably a scan IC on the Y buffer board or an FET on the Y sustain or z sustain boards.
All of these boards are board level repair,you need to replace the defective board in order to repair the tv set.
I'm not sure about your electronic or tv repair background,but if you have any,and some equipment(multimeter),you could try to fix this yourself.
The Y sustain board is the one to the left from power supply(from the back).
Check any fuse on this board-if any is open=replace the Y sustain.
Same thing for the Z sustain-the one far to the right from the back)
if no open fuse on any of the Y sustain or Z sustain-then some voltage readings will be necessary to diagnose the defective board.
-Vy,is a voltage on Y board-if is too low,disconnect the Y buffer and check again.I voltage comes back up(around-190V,see the exact value on the panel label),then replace the Y buffer.
If still to low,then replace the Y sustain.
It may seem confusing,but these are the steps for a complete diagnose!
Based on my experience with these LG/Zenith units, about 90% of the time is the Y sustain board.
The best way,is to get the part# XXXXX from the board itself,it is written on a label onto the board .
A good place to start looking for the part is ;
I hope this helps,
Thank you and have a great day!