User`s manual

Dolby
®
CP650 Digital Cinema Processor User’s Manual Reference Information
C-4
C.3 Test and Demonstration Films
Several test and demonstration films produced by Dolby Laboratories are available
from your equipment supplier. For proper system maintenance, the Cat. No. 69T test
film is required, and the Cat. No. 251 Jiffy test film is strongly recommended. The
Cat. No. 69T test film should be formed into loops for ease of use. Other test films are
for use by your service engineer with special test equipment.
Cat. No. 69T—Dolby Tone
Figure C-5 Cat. No. 69T Dolby Tone Test Film
The Cat. No. 69T is required to maintain your theatre system. The Dolby tone
recorded on the film is used during automatic calibration of the operating level in the
CP650. This simple procedure must be performed whenever an exciter lamp or
soundhead LED is replaced, and should also be performed regularly to compensate
for normal aging (and resultant lower sound output on analog soundtracks).
Why is adjusting Dolby level important? The accurate reproduction of analog Dolby
soundtracks requires that the decoders in the theatre act as precise mirror images of
the encoders used when the tracks were recorded. This precision is ensured in two
ways. First, the circuits are manufactured to very close tolerances. Second, a
reference Dolby level has been established so that any Dolby encoded film can be
accurately decoded by any Dolby cinema processor.
Cat. No. 251—Jiffy Test Film
We strongly recommend that you obtain the Cat. No. 251 eight-minute test film to
help keep your system sounding its best. No special equipment is required; the tests
have been specifically designed to permit subjective judgment by ear. Each test is
described by a male or female voice, and is supplemented by captions on the screen
that help identify the causes of sound system problems. Visual checks are also
included to assist in identifying some picture projection problems.
Tests provided on the Cat. No. 251 include level set, channel identification, channel
level, loudspeaker equalization, loudspeaker and amplifier condition, projector wow
and flutter, overall system performance, visual checks, and a noise and interference
test.