Installation manual

Dolby
®
Model CP650 Installation Manual
9-1
Chapter 9
Maintenance and Troubleshooting
9.1 Print Cleanliness
As with any soundtrack, keeping the film print clean will give best performance. The
Dolby
®
Digital print format has robust error correction information encoded along
with the audio data, and the CP650 uses a powerful digital error-correction technique,
allowing the data to be read perfectly even if scratches and dirt are present. However,
best performance will be obtained if the print is kept clean. Standard film cleaners
will provide good results.
The sound quality of the digital track has properties unlike those of an analog track
with regard to print wear. With any analog track, print wear will degrade quality in a
more or less linear fashion; the more wear, the lower the quality of the sound. With a
digital soundtrack, wear will have no audible effect until the picture quality is
degraded beyond use. At this point, wear may exceed the error correction capabilities
of the Dolby Digital decoder, and the CP650 will automatically switch to the analog
Dolby SR track.
Quality
Number of plays
ANALOG
DIGITAL
(Sound & Picture)
Figure 9–1 Digital/Analog Track Wear
9.2 Digital Soundhead Maintenance
The digital soundhead should be kept clean and free of dust and dirt for best
performance, just like the analog soundhead. Wiping the external surfaces with a
clean cloth on a regular basis will keep the head looking new. The optical path should
be inspected regularly and kept clean with a photographer’s lens cleaning kit
(available from most camera stores). Use care not to scratch the lens. The film path
(rollers and drum) should be cleaned regularly, as you would on the projector.
Acetone, carbon tetrachloride, and other dangerous cleaners should not be used.