Inverter Board

Hi everyone, its my first post here and i trying to get some help about a problem on the laptop of my mom.

She has an acer aspire 6920g ( 4-5 years old ) 2 weeks ago the screen was almost fully black(I could hardly see anything ) but if i connect another monitor to the laptop with a HDMI cable everything is fine. After some research on google, i found that the problem were comming from the inverter board, so i bought a new one and i installed it last week. The problem was solved but since this morning the problem is back. Does the problem is still the inverter board ? or maybe a cable linked to the inverter board ?

Sorry about my poor english.

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