Unscrew all screws holding outer cover.

Lift cover to expose whole back of the panel and backlight board.

Unscrew the cover and lift it. Inspect circuit board for corrosion and treat it with the contact cleaning spray. Remember about the tape connector as it can have corrosion on its contacts.

Also remove corrosion from the panel shielding. It usually spreads from the outer sides as marked on the picture. Corrosion can spread to connectors and circuit board. Make sure you removed all of it. You can use high gradation sandpaper, but do not do it over the display.