User`s manual

Dolby
®
CP650 Digital Cinema Processor User’s Manual Maintenance and Calibration
3-2
will depend on your theatre’s hours of operation. Use only a General Electric EPT,
reflector-type, 42 watt lamp (Dolby Part Number 34010).
To replace the exciter lamp:
1. Disconnect AC mains power, then carefully remove the six
screws holding the rear cover/power supply assembly.
2. Allow the lamp to cool, if necessary. With the rear cover
removed, the lamp will be visible but still attached to the
rear cover assembly by its two supply wires. Slide the
lamp out of its mounting bracket, then remove the lamp
from the socket.
3. Using gloves or a clean, lint-free cloth, carefully remove
a new lamp from its protective box. Place the new lamp
in the socket. Be careful not to touch the bulb or inner
surface of the reflector in the lamp. If either is
accidentally touched, carefully clean the area with
isopropyl alcohol when the bulb is cool. Allow time to dry.
4. Slide the lamp back into its bracket in the soundhead, replace the rear cover assembly,
and tighten the six screws.
3.2 Dolby Level Calibration
Proper decoding of soundtracks encoded with Dolby processing requires careful level
matching of each channel. When the CP650 was first installed, the technician made
this adjustment. We recommend that you routinely perform these steps to compensate
for the normal aging of the optical soundtrack light source. It is always necessary to
adjust Dolby level whenever an exciter lamp is replaced. (See Appendix C.3 for a
description of why Dolby level is important.)
The CP650 has an automatic level adjustment facility for easy calibration. A loop of
Dolby Cat. No. 69T test film is required for this adjustment. The test film is available
from your theatre equipment supplier.
1. On projector 1, clean the optics as described earlier.
2. Thread and play the Cat. No. 69T Dolby tone test film. Ensure that the arrow is going
in the correct direction. The film emulsion should face away from the screen.
3. Switch the booth monitor to Center channel.
4. Listen to the tone on the booth monitor to identify any problems with distortion or
speed variations. Call your service technician if you hear problems.