MacBook Pro A1226 Backlight won't stay on

lcd screen had dead pixels replaced it. backlight did not work, put old screen in. still no backlight can see dim desktop , external monitor works fine.
replaced led driver board (often mistakenly identified "inverter") , cable, still no backlight. replaced mag-safe board, still no backlight. however, notice backlight flash on 1/2 second when awakened display sleep. (think same thing @ start-up, it's hard tell because of neutral background). it's possible flashing on before swapped parts , didn't notice.

have idea on what's going on?

 

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