2 . G e n e r a l D e s c r i p t i o n
CHRISTIE INC. - 35/70 Service/PM Manual
July, 1997
desired show, and waits for the command that will start play. This motion may be either forward or reverse depending on
the position of the next show relative to the current show.
Certain commands input from the keypad or the remote interface (the show controller or a service terminal) suspend
normal operation and allow the user to examine system state or modify constants for troubleshooting. In this mode, all
film motion and other projector functions may be controlled manually.
Monitoring Projector Performance
Film advances through the projector in one of two ways. In
cine motion
, when a show is playing, the projector jerks, or
pulls a film frame into position, synchronized with the closed portion of the shutter. Each advance of the film is called a
pulldown. In
slew motion
, when advancing or rewinding to a new cue position, the film moves smoothly, and the douser
prevents image projection.
Picture quality is maintained by several automatic systems, which function without operator assistance.
Proper framing of the film in the gate is monitored during every pulldown. If an out-of-frame condition is detected, the
projector determines the number of perforations in error and corrects the error during the next pulldown by pulling either
more or less film, as appropriate. The pulldown is automatically synchronized with the shutter as the running frame rate is
reached. This automatic process maintains a “ghost-free” picture. The shutter action is adjusted during the manufacturing
process; shutter adjustments are not normally required.
Another automatic system maintains a jitter-free picture by positioning the film in the gate in a manner that corrects for
temperature changes, film type, gate pressure, and other conditions that would otherwise require operator adjustments.
The projector has been designed with built-in safety features to protect the film in case of malfunction. One such feature
is the douser interlock relay, a solid-state relay that allows the douser to open only if the film is moving forward. This
prevents the possibility of film burns due to an electronic malfunction. In addition, latching LED indicators help in
troubleshoot problems if they occur.
The constant-velocity drive sprocket, pulldown, and shutter motor systems are controlled by a microprocessor that
normally phase-locks all rates to the line frequency. When the system powers up, the processor determines whether the
line is at 60 or 50 Hz, and sets the proper multiplier to maintain the system clock at 192 KHz. Crystal operation may be
selected by a jumper plug on the Central Processing Unit/Main Logic card.
