We’ve received this iPhone 6s from Tanzania, East Africa and customer tried to replace LCD screen and unfortunately he damaged the LCD FPC connector and backlight filter on this iPhone6s. so we’ve replaced the LCD FPC connector and also replaced the backlight filter with new one and after that phone starts working without any issue.
Repairing a Dead iPhone 6s with Shorted Capacitor on PP_VCC_MAIN
iPhone 6S Backlight Circuit Repair – Coils, Diodes, Capacitor
iPhone 6S no backlight, no image solved after failed attempts by Another Technician .