Instead of a parallelogram mechanism here a chain drive ensures that the TV direction is kept unchanged when it moves up down.
The grey sprocket is stationary. The TV back is fixed to the other sprocket (in yellow).
Red springs equilibrate the mechanism. Positions of the spring pivots are the key factor. They should be defined during testing the mechanism to ensure that when spring force is increased, its lever arm for right revolution joint of the blue bar is reduced.