5 : T h e o r y o f O p e r a t i o n
CHRISTIE INC. -
CHRISTIE INC. - 35/70 Service/PM Manual
July, 1997
Figure 5.1: 35/70 Electronic Projector Block Diagram
The incremental motion of the film in the gate is taken up by the film loops maintained for this purpose. The upper and
lower torque motors are controlled by the position of the respective torque arms, and operate to maintain the torque arms
stationary, independently of the amount of film on the supply and take-up reels.
During slew operation the speed and direction of the constant velocity motor is controlled by the CPU. The pulldown
motor is slaved to the constant velocity motor so film moves through the film gate smoothly. During slew operation, the
douser blocks the illumination of the film.
In interlock operation, the CPU signal that controls the Constant Velocity motor is replaced by an external interlock
signal. This interlock signal, when supplied from a Master projector, is derived from the pulses coming back from the
C.V. motor of the Master projector. The remainder of the operation remains the same.
Additional functions such as beginning of show and end of show sensing and control of various projector elements are
also provided by the CPU.
