I can tell that you came to take a look so I will give you your answer and trust you will do the right thing and rate me positively after reading it.
I`ll start by saying that the LED strips problem is very common for those LG of the LN serie and it certainly sounds like this now.
You were asking about the voltage that should be there ?
Take a look near the AC connector and you will see it printed on the board , one output runs at 100 and the other at 111 volts when working normally .
Now if you were to set your meter on those 75 volts pin and turn on the tv then while you see that flash on the screen those pins may peek at 150 + volts and then go back down to 75 volts , that's the control circuit shutting it down due to over voltage caused by opened LED`s
So to answer your question , your led strips need to be replaced .
Look at the link below for a set of 12 ;
If that answers your question please do not forget to rate by clicking on the 5-star icon at the top, then click on Submit so i get paid for my time helping you .
Also note that it will not close this post , you can come back here at any time if you have questions.