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T H E O R Y O F O P E R A T I O N
This section describes the theory of operation for the 35/70 projector. The description introduces a general view at an
overall block diagram level, and then details the function of each block in subsequent paragraphs. Circuit diagrams and
component layouts for each card are found in Section 8 of this manual.
The projector is self-contained except for the power supply and control console. The projector houses most of the
electronics, as well as the position encoders, power amplifiers, and motors.
Functional Description of the Projector
The overall block diagram of the projector is shown in Figure 5.1. Projector operation depends on five motor systems
which deal with the shutter timing and film motion in both cine (also called pulldown) and slew (also called high-speed)
modes.
• Shutter Control Circuit
• Constant Velocity Control Circuit
• Pulldown Motor Control Circuit
• Upper Torque Motor Control Circuit
• Lower Torque Motor Control Circuit.
The interrelationship and timing between these circuits is shown schematically in the film velocity diagram and the system
timing diagram, both in Section 8.15 (Miscellaneous Diagrams).
The Shutter Control Circuit and the Constant Velocity Control Circuit are directly controlled in both cine and slew motion
modes. The desired film speed is normally 30 frames per second in cine, and 120 frames per second in slew mode. The
shutter rotation speed is normally 30 rotations per second. The microprocessor CPU generates signals which are used to
precisely control these two motor speeds, which are locked to the line frequency using a phase locked loop.
The shutter has two openings, so the film frames are illuminated 60 times per second. In cine operation, the pulldown
motor must move the film in such a way that a frame is stationary in the film gate during two illuminations, and then must
move a new frame of film into the gate during the closed portion of the second shutter cycle. The shutter provides an
index signal to the pulldown circuit which indicates the precise moment of shutter closure, and initiates the pulldown
action. The next frame is pulled into place, and held in registration by monitoring an edge indication from the slots on the
pulldown disk encoder.
CHRISTIE INC. - 35/70 Service/PM Manual
CHRISTIE INC. -
July, 1997
5 : T h e o r y o f O p e r a t i o n
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