Bpt old tv intercom screen black/white

[yanir]

Hello
I have bpt old screen intercom in my common dipartment and i see black screen, but i can talk and open the gate via buttons

Evrey body know how i fix the davice
Circuit diagram ,parts and What could be the fault?

 

[sparkymarka]

Is it a multi user system ? If so First step ask other people in block does it work ? If so then it narrows it down to your unit ….if not then I would be looking at the power supply or the camera module