Won't power on.

Chevron comes on only if unplugged and plugged back in. When screen bl tries to come on TV shuts down and power button has no effect.
Suspect bad string of LEDs but how do I isolate bad string when power won't stay on to read voltage?

Re: New Members - please post your introductions here

Hello everyone I’m Mike. Just wanted to mention I read the entire first page of this thread and the entire last page (was not expecting to be almost 1000 pages in between)
So here goes my first P.C. was a TI-99 then a 64. I’ve since seen and worked on so many different types of electronics that I’ve lost count.
This seems like a great community to learn and share knowledge for the benefit of all.
Thanks for all the great information that is available.