Per the AG-1980P user manual (page 4) if dew is sensed the display should flash the letter "d" but that assumes things are working normally.
This old thread discusses some possibilities.
Do you see any indication of the display?
You should be concerned about the caps in the deck, Symptoms include dim display and picture issues such as "barber pole" like noise.
The FSM documents some diagnostics that can be run in service mode.