Repair of the dashboard backlight audi 100 c4

Good time of day. today I will tell you how to solve the problem of non-working illumination of the appliance on AUDI 100 \80, the problem appeared suddenly, the bulbs were changed, but there is no result. The instrument panel had to be removed and disassembled to view the board. Everything is done with your own hands, without having an education, but having the desire and hands.