Join Date: Feb 2013
Location: The Outer Limits....Don't trust any air I can't see ☺
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That part is a MIL light (malfuntion indicator LED ) it is there to display a diagnostic fault code for a repair technician the fault may or may not be on that board.
A service manual would be a lot of help note how many times the light blinks before it cycles , google what you see as to the power board blinking someone may know the code.
It may be a power board fault another board fault or a connection.or bad solder joint in the board when it heats up . Also look for bulging capacitors on the board if you haven't already.
Common power board faults are failed capacitors and errant or failed voltage regulators and cold solder joints. that would include all brands.
When your screen goes dark leave it on shine a flashlight into the screen it if you can still see the picture working then your backlight is out, since you already replaced the baclklight inverter board it could well be be a fault on the power board .There may be voltage output markings on the power board near the connectors those can be checked as well with a DVM.
The power board in addition to feeding the Tuner, Panel T-Con Board,Video and control panel boards has to also feed the back light inverter board . If one of the voltage rails feeding the inverter board fails you will see darkness
just as if the inverter board itself were bad .