Dolby Laboratories CP45 User manual

MODEL CP45
CINEMA PROCESSOR
Users' Manual

USERS' MANUAL
FOR
MODEL CP45 CINEMA PROCESSOR
Dolby Laboratories Inc
U.S.A. 100 Potrero Avenue, San Francisco, CA 94103
Tel: [phone]; Fax: [phone]
U.K. Wootton Bassett, Wiltshire SN4 8QJ, England
Tel: [phone]; Fax: [phone]
Dolby is a registered trademark of Dolby Laboratories Licensing Corporation.
©1995 Dolby Laboratories ISSUE 1
S95/10750
Dolby Part No. 91388

TABLE OF CONTENTS
INTRODUCTION
SECTION 1
OPERATING INSTRUCTIONS ............................................................................................ 1-1
A. NORMAL OPERATION
1. Initial Power-Up..................................................................................................1-1
2. Format Selection..................................................................................................1-1
3. Local (Front-Panel) Fader..................................................................................1-3
4. Remote Faders .....................................................................................................1-3
5. Mute Function......................................................................................................1-3
B. OPERATION WITH AUTOMATION SYSTEM ....................................................... 1-4
C. BYPASS OPERATION................................................................................................... 1-4
SECTION 2
MAINTENANCE AND ADJUSTMENTS........................................................................... 2-1
A. SOUNDHEAD MAINTENANCE............................................................................... 2-1
B. PRINT CLEANLINESS .................................................................................................. 2-2
C. DOLBY LEVEL ADJUSTMENT................................................................................... 2-2
SECTION 3
TROUBLESHOOTING ............................................................................................................ 3-1
A. DURING THE SHOW
1. If Film Sound Is Lost ..........................................................................................3-1
2. If One Channel Fails or is Distorted................................................................3-2
3. If Switching to Bypass Does Not Restore Sound..........................................3-2
4. Excessive or Inappropriate Sound from the Surround Speakers .............3-3
B. BETWEEN SHOWS ........................................................................................................ 3-3
C. WHEN THE THEATRE IS CLOSED .......................................................................... 3-4
D. TROUBLESHOOTING CHART .................................................................................. 3-6
APPENDIX A
HOW TO TELL A STEREO OPTICAL PRINT
FROM A MONO PRINT ........................................................................................................A-1
APPENDIX B
DOLBY TEST AND DEMONSTRATION FILMS........................................................... B-1
1. Cat. No.69T: Dolby Tone ................................................................................ B-1
2. Cat. No.251: Jiffy Test Film ............................................................................ B-1
3. Cat. No.351 Stereo Demonstration Film: “listen . . .” ............................... B-3
4. Other Test Films ................................................................................................. B-3

APPENDIX C
CP45 MODULE DESCRIPTIONS........................................................................................ C-1
APPENDIX D
ABOUT DOLBY FILM SOUND FORMATS .....................................................................D-1
1. How Dolby Noise Reduction Works..............................................................D-1
2. About Dolby SR..................................................................................................D-1
3. Why the Dolby Level Adjustment Is Important..........................................D-3
4. The Consumer Dolby Noise Reduction Systems.........................................D-3
APPENDIX E
HOW FOUR CHANNELS ARE DERIVED FROM
DOLBY STEREO OPTICAL PRINTS...................................................................................E-1
APPENDIX F
OPTICAL BASS EXTENSION ...............................................................................................F-1
APPENDIX G
CINEMA SOUND AND THE EVOLUTION
OF DOLBY FILM SOUND.....................................................................................................G-1

i
INTRODUCTION
WHY A CINEMA PROCESSOR?
Originally, stereo sound on motion picture film was possible only by means of
magnetic striping, which was introduced in the 1950s. Although capable of
very good sound, this was such a costly approach that by the 1970s relatively
few films were being released with stereo soundtracks.
Then in 1975 Dolby Laboratories introduced the stereo optical soundtrack
originallyknownasDolbyStereo.Itprovidedthemultichannelsoundassociated
with magnetic soundtracks in a much more practical format.
Getting high-quality stereo sound from an optical soundtrack required the
application of several new processes. It was necessary, for example, to
electronically “fold” four sound channels into just two physical tracks on the
film, and then “unfold” (decode) them on playback in the theatre. Dolby noise
reduction,aformofsignalprocessingthatgreatlyexpandsthelimiteddynamic
range of optical soundtracks, was also used, and requires its own special
playback processing circuitry.
Thus the cinema processor was introduced as a new element in theatre sound
systems. In addition to properly decoding Dolby encoded soundtracks, Dolby
processorssuchastheCP45alsoprovideequalizationcircuitsthatoptimizethe
frequency range of the projector’s optical soundhead and the theatre
loudspeakers. The diagrams below show the role cinema processor plays in
bringing your audiences thrilling, multichannel Dolby sound.
EQ
EQ
EQ
EQ

ii
About The Dolby CP45
Once installed, the Dolby CP45 Cinema Processor becomes the heart of your
theatre sound system. All sound sources are connected to the CP45, which
processes their signals appropriately and feeds them to the power amplifiers.
TheDolbyModelCP45providesthehighperformanceforwhichallprocessors
manufactured by Dolby Laboratories are known in a new cost-effective,
integrated design. Its many features include a stereo optical preamp with
precise slit-loss correction, processing for both Dolby A-type and Dolby SR
soundtracks,anadvanced2:4-channeldecoder,andmulti-bandscreenspeaker
equalization.Theseadvancedcircuitsensureaccuratereproductionofallfilms
with Dolby analog soundtracks, and permit the theatre to use the widely-
respectedname“Dolby”onthemarqueeandinadvertisingtoidentifypresenta-
tions of Dolby releases.
Additional standard features of the CP45 are a built-in fader with remote
facilities,simplepush-buttonsoundtrackformatselection,andcomprehensive
fail-safefeatures that includea built-inbypass system. The unitalso interfaces
readily with theatre automation systems.
The CP45 supports the following sound formats:
Format Number
Mono 01
Dolby A-type (stereo) 04
Dolby SR (stereo) 05
Non sync 1 60
Non sync 2 / Aux 61
Microphone 64
About This Manual
ThisUsers’Manualhasbeenpreparedspecificallytohelpprojectionistsgetthe
most from the Model CP45 and the theatre sound system once it has been
installed and aligned. (Installation and alignment instructions are supplied to
the local distributor or installation company). We suggest that you keep this
manual readily available.
The manual is organized as follows:
• Section 1, Operating Instructions, covers the basic control functions
and operation of the CP45.
• Section 2, Maintenance and Adjustments, contains tips for
maintaining the CP45 and the theatre sound system.

iii
• Section3,Troubleshooting,willhelpyoutrackdownproblemsinthe
soundsystemwithouttestequipment.Itconsistsofatroubleshooting
chart and procedures to follow during a show, between shows, and
after closing.
• The Appendices contain valuable background information which
will help you to get the most out of the Model CP45 and your theatre
sound system.
For the sake of clarity, boldface type is used for all specific references to the
CP45 controls and their labels, such as Bypass, and front-panel Fader. In
addition, indicator lights on the CP45 are referred to in the text as LEDs (light-
emitting diodes).

1-1
SECTION 1
OPERATING INSTRUCTIONS
A. NORMAL OPERATION
1. Initial Power-Up
Each time the CP45 is connected to power, it automatically sets itself to
the format it was in when power was removed unless the power has
been removed for more than a week. Under these circumstances the
wake-up state is:
• Format 01 Mono
• Front-panel (Local) fader activated
•Proj 1 or Proj 2 LED illuminated, indicating the externally-
selected projector that is active (Proj 1 can be set to be selected
automatically if no external selection has been made although it
is usual for the individual projectors to be selected for bypass
mode flexibility).
2. Format Selection
Select the desired film soundtrack format or your non-sync source by
pressing the appropriate button. The LED in the button illuminates to
confirm that the format was selected. The formats are as follows:
•01 Mono: for all optical prints of any vintage with conventional
mono optical (“Academy”) soundtracks.
•04 Dolby A-type: for Dolby Stereo releases, except those marked
SR or Digital.
•05 Dolby SR: for releases marked as having a Dolby SR
soundtrack. (If your CP45 is not equipped with the SR circuit
needed to play SR copies, 04 Dolby A-type can be selected.)
•60 Non-sync 1: for your music tape or CD player.
•61Aux/Non-sync2: this format may be programmed in a number
ofdifferent ways dependingon theoptional equipment fittedand
the installation. Possible options include:
Magnetic soundtracks from projectors or followers with
appropriate magnetic preamplifiers.
Extra sound sources (consult your service engineer for details).

1-2
Figure 1. CP45 Front Panel Control
SignalSignal
SystemSystem
FormatFormatFaderFader
faderfader
activeactive NormalNormal
BypassBypass
LeftLeft
RightRight
CenterCenter
Sub WooferSub Woofer
SurroundSurround
MicMic
MonoMono
1010
00
Projector 2Projector 2
Projector 1Projector 1
33
22
11
88
77
99
66
55
44
Non-sync 1Non-sync 1
Aux/Non-sync 2Aux/Non-sync 2
Dolby Stereo A-typeDolby Stereo A-type
Dolby Stereo SRDolby Stereo SR
6161
6060
6464
0505
0101
0404
FADER ACTIVE INDICATOR
Shows if the front panel fader
has been selected.
FRONT PANEL FADER
Controls the auditorium level
when selected. The control
should be set at or near 7 for
normal operation.
PROJ 1/PROJ 2 INDICATORS
Show which projector has been
selected.
Normal fader setting.
FORMAT 01
For mono optical
soundtracks.
FORMAT 04
For Dolby Stereo soundtracks
except those marked SR or SR•D.
FORMAT 05
For Dolby Stereo SR
soundtracks.
FORMAT 60
For non-sync, background
music from a cassette
deck or CD player.
FORMAT 61
For extra sound sources.
BYPASS INDICATOR
Flashes if the CP45 is in bypass mode.
The CP45 will automatically switch to
bypass if the internal power supply fails.
SIGNAL PRESENCE INDICATORS
These will light if a signal is present
on the indicated channel.
BYPASS/NORMAL SWITCH
For manually switching to bypass if
there is a problem. Switches to a
separate power supply.
FADER ACTIVE BUTTON
Switches the fader control back
to local (this fader) if remote
faders are installed.
FORMAT 64
Selects the microphone for public
announcements. If the CP45 is in
bypass mode, push and hold this
button to make an announcement.

1-3
•64 Mic: for public address announcements in the theatre.
Thefilm soundtrackformat numbers used onthe CP45front paneloften
appear on the film can and leader. If these numbers are not supplied
and you are not sure if a print is mono or stereo optical, see Appendix
A for a means to distinguish mono from stereo optical soundtracks.
If you are playing an early Dolby Stereo release and it is marked as
format 03 “Dolby Stereo without surround,” select format 04 Dolby A-
type.
3. Front Panel (Local) Fader
The fader on the front panel of the CP45 controls the volume level in the
theatre in all operating modes. After the CP45 has been correctly
installed, setting the fader to 7 will play a Dolby film at the level at
which it was mixed.
Although a minor adjustment in playback level might be required
under unusual circumstances, you should avoid significant deviations
from the correct level (7) established by the installer. If the playback
level is set too low, dialogue will be hard to understand; too high a level
will give rise to complaints from the audience and under extreme
circumstances can damage the theatre’s sound system.
4. Remote Faders
Inadditiontothefrontpanel (local)fadertheCP45canalso be controlled
by an external remote fader.
If a remote fader has been installed, it is activated by pressing the select
button on the remote. The local front panel fader LED will go off to
indicate that the remote fader has been activated. To regain local
control, press the “fader active” button located below the front panel
fader. The button will have no effect if there are no remote faders.
5. Mute Function
When you press the mute button on the remote unit (if installed), the
volume will automatically fade all the way down. When you press the
button again, the volume will automatically rise to the level set by the
fader which is in control of the level (local or remote fader).
The Mute button is useful if the film breaks or runs out with the
projector active since it supresses the very loud signal that occurs when
a leader or tail passes through the sound gate.
If the CP45 is not conveniently close to the projector and there is a
remote fader at the projector, use the following procedure to start the
show:

1-4
• Fade out the intermission music with the local front panel fader.
• Move to the remote location and see that the fader there is at 7.
• Select the film format.
• Start the projector.
• After the film leader has passed through the gate, select the
remote fader and trim the level slowly if necessary.
Followingtheaboveprocedureshouldpreventtheaudiencefromhearing
annoying thumps and leader crackle at the beginning of the show.
B. OPERATION WITH AUTOMATION SYSTEMS
If the CP45 in your theatre is connected to automation equipment, the
format buttons and their associated LEDs may be duplicated elsewhere.
In most cases, the front panel controls of the CP45 can usually be used
to override commands from the automation system; however, as
automation equipment differs from installation to installation, check
with the installer of your system if you have any questions about its
operation and whether you can easily override automation commands.
C. BYPASS OPERATION
The CP45 has an independent power supply for emergency operation.
If the main power supply or processor circuitry fails, the unit will
automaticallyswitchtobypassoperation, allowingtheshowtocontinue
with limited sound processing functions. Bypass operation is signalled
by the flashing of the bypass LED on the front panel.
In the case of other problems, such as distortion or the loss of a channel,
the bypass mode can be selected manually by means of a switch located
on the front panel. However, there are other components in the theatre
sound system that could also fail. Be sure to refer to Section3,
Troubleshooting, any time there is a problem.
The following occurs when the CP45 is switched into the bypass mode:
• The front-panel remains operational but remote faders will not
work.
• Although you can select formats to help with faultfinding, the
commands from the front panel are ignored by the unit. The
optical preamp output of the selected projector and (if so
programmed at installation) the Non-sync and/or Aux inputs all
remain operational simultaneously. If you are not playing film,

1-5
be sure that the projector is not selected. If you are playing an
optical film print, be sure that there are no signals present from
any of the other sound sources.
• Even when a stereo print is playing, a summed mono signal is fed
to all the screen speakers. Thus, you can switch to the bypass
mode to keep the show going if one of the power amplifiers or
speakers fail.
• The Dolby A-type noise reduction circuitry, Spectral Recording
processors, 2:4-channel decoder, screen speaker equalizers,
surround equalizers, and subwoofer circuits are out of the signal
path.
• The front panel mic switch acts as a "push to talk" key rather than
a "push on, push off" switch. If there are emergency
announcements to make, the film and background music should
be turned off so that the audience can hear the announcement
above the other sources of sound.
If the unit has entered bypass mode due to a failure in the main power
supply or the main power source, then the front panel LEDs will be off
except the projector select and bypass LEDs. The unit performs in
exactly the same way as if the bypass switch were selected as described
above.
In the event of bypass operation, be sure to follow the troubleshooting
procedures and call your trained service engineer, if necessary, as soon
as possible.
NOTE
TheCP45willnotoperateeveninthebypass
mode if there is a fault in the mains supply
to the bypass transformer and may not
operate if there is a fault in either the Cat.
No. 514 optical preamp card, the bypass
circuitrysectionoftheCat.No.510onwhich
it is mounted, or the bypass power
transformer itself. It is strongly
recommended that a spare of both of the
cards and the transformer block be kept on
handfor substitution inemergencies. If the
theatre is equipped with film platters and
the unused projector input on the rear of
the CP45 is accessible, the projector solar
cell leads can be moved from P1 to P2 in
ordertotryusingthesecondopticalpreamp
circuit, however this input may not be set
up correctly so care will be needed with the
volume control.

1-6
WARNING
The CP45 was adjusted initially by a
specially-trained engineer so that your
theatre would have the same standard
playback characteristics as the dubbing
theatres in which all Dolby encoded films
aremixed. This results inthe most accurate
reproduction possible. Never attempt to
adjustanycontrolswithintheCP45except
those specified in this manual.
All other controls are for use by a trained
engineer when the CP45 is first installed or
repaired. Adjustingthesecontrols requires
the use of special test equipment.
Misadjusting these controls can have an
adverse effect on the sound in your theatre
and will require a service call to restore
proper operation. The first thing to do
when you have a problem is to consult
Section 3 Troubleshooting, and not
randomlyadjustthese specializedcontrols.
Inaddition,donotadjustanyofthecontrols
on the other audio equipment in your
theatre sound system such as power
amplifiers, which have been preset by the
installer. For example, misadjusting the
power amplifier gain controls can cause
channel imbalance and/or too much power
amplifier noise. Those controls have been
set by the installer for correct channel
balance and so that the playback level in
the theatre is correct with the fader set to 7.
If a satisfactory level can only be achieved
with the fader set to some other level, the
gain controls on the power amplifiers have
been touched and have now to be
recalibrated by a service engineer.

2-1
SECTION 2
MAINTENANCE AND ADJUSTMENTS
TheinstallationoftheDolbyCP45inyourtheatreindicatesacommitment
to providing a high-quality presentation to your audiences. However,
thepresenceof even theverybest equipmentdoesnotin itselfguarantee
the best results. A number of routine maintenance and adjustment
procedures,requiringnospecialtest equipment ortechnicalknowledge,
are necessary to realize the full potential of the sound system on a day-
to-day basis. These procedures can also prevent costly show
cancellations and service calls.
A Dolby Cat. No. 69T test film is required for proper maintenance of
your sound system. We also recommend that you keep on hand the
Dolby Cat. No.251 Jiffy Test Film and run it regularly to check the
theatre sound system thoroughly (see Appendix B).
A. SOUNDHEAD MAINTENANCE
No single maintenance procedure is more vital to good sound in the
theatre than regular cleaning of the projector soundhead optics. Use
lint-free cotton swabs and isopropyl alcohol to clean the optical barrel
lens surfaces, but, under no circumstances touch or attempt to clean the
solar cell. The solar cell and its adjustment are extremely delicate. We
stronglyrecommendthatyouusecompressedair,availableinconvenient
pressure cans, to blow dirt and debris away from the cell. But be
absolutely certain that the nozzle cannot ever touch the cell.
Figure 1 Cleaning the Soundhead Optics

2-2
Figure 2 Never touch the solar cell
B. PRINT CLEANLINESS
A high fidelity Dolby Stereo theatre system is like a high-quality home
stereosystem: it cansound only asgood asthe programmaterial played
through it. A good theatre system will reproduce pops, crackles, and
other unwanted noises from worn and dirty film prints.
If you receive a poor print from your distributor, there is little you can do
except, if possible, arrange for its replacement. But while a print is in your
theatre, you should treat it with respect and care to be sure your audiences
receivethebestinbothsoundandpicture. Ofgreatestimportance,theprint
shouldbekeptascleanaspossible—whenthefilmisplayed,whentheprint
is stored between shows, and when a platter reel is made up (if your theatre
is so equipped). In particular, when individual reels are unwound to make
up a platter reel, do not let the film touch the floor or come in contact with
other sources of dust and dirt.
C. DOLBY LEVEL ADJUSTMENT
ProperdecodingofsoundtracksencodedwithDolbyA-typeorSRprocessors
requires careful level matching between each channel of each soundhead
andtheCP45(seeAppendixDforadiscussionofDolbynoisereductionand
why Dolby Level is important). When the CP45 is first installed, the
installermakes thisadjustment foryou. However, itisalwaysnecessaryto
adjust Dolby Level whenever an exciter lamp is replaced. We also
recommend that you routinely check Dolby Level but only adjust it to
compensate for the normal aging of the exciter lamp if necessary. Always
clean the optics first.
Checking and adjusting Dolby Level requires a loop of Dolby Cat. No. 69T
test film that is available from your theatre equipment supplier. You will
alsoneed thealignment toolsupplied withthe CP45or a small screwdriver.
X

2-3
5. Locate the Cat. No. 510 card and Cat. No.
222 noise reduction module. (Dolby Level
adjustments are made on the Cat. No. 510
while the LEDs on the Cat. No. 222 module
indicate when Dolby level is achieved.)
4. Open the front panel of the CP45 using a
screwdriver.
3. Threadthe loopof DolbyCat. No.69T test
film on the projector and play the Dolby
Level tone (with its characteristic warble).
Be sure that the emulsion side of the film
faces towards the projector exciter lamp.
The film must run in the direction of the
printed arrow.
The adjustment procedure is as follows:
2. Select format 01 Mono.
1. Clean the soundhead optics (see part A above).
FormatFormat
MonoMono0101

2-4
6. Turn the projector on.
7. As the test loop is played, watch the LEDs on the Cat. No. 222A/
SR. Correct Dolby Level is indicated when the two center green
LEDs for each channel are equally bright. If necessary, adjust the
Left and/or Right gain controls (mounted on the front edge of the
Cat. No. 510) for the projector in use so that the pair of green LEDs is
equally lit. Be very careful not to adjust the adjacent, recessed hf
control by mistake; if this control is inadvertently changed, a service
engineer with special test equipment is required to readjust it.
PROJECTOR 1
LEFT RIGHT
LEVEL LEVEL
PROJECTOR 2
LEFT RIGHT
LEVEL LEVEL
Dual SR/A Decoder ModuleDual SR/A Decoder Module AASRSR Cat.No.222SR/ACat.No.222SR/A
Dolby
CAT. NO. 510
LR
8. Repeat the above procedure for the other projector.
NOTE
If you happen to play the test film with a stereo optical format (04 or 05)
selected after Dolby Level has been correctly adjusted, you may notice that the
pairs of green LEDs are not equally lit or that one or both of the left hand side
LEDs goes out completely. This is normal, and represents a very small (less
than 0.5 dB) level difference when the Dolby noise reduction circuitry is
switched on for the stereo formats.

3-1
SECTION 3
TROUBLESHOOTING
Your theatre sound system consists of a number of critical audio
components in addition to the Dolby CP45. Thus, the first step when
something goes wrong with the sound is to find the source of the
problem. The troubleshooting chart starting on page 3-6 can be helpful.
If the troubleshooting chart is not sufficient for finding and solving the
problem right away, the procedures in the following paragraphs should
be helpful. Each paragraph is gauged to the time available for
troubleshooting; during a show, between shows, and after closing. In
addition,AppendixCcontains briefdescriptionsofeach circuit module,
which will further help you to track down any problems with the CP45.
If you are unable to solve the problem using the information which
follows, call your local authorized service engineer.
A. DURING THE SHOW
1. If Film Sound Is Lost
• Check that the correct projector is selected.
• Check to see if the exiter lamp on the active projector is on.
• Check to make sure that the power amps are on.
• Immediately switch the CP45 to bypass. (Push up the small slide
switch on the right hand side of the front panel under the green
signal present indicators). If sound is restored, troubleshooting
can be performed later.
• Check to see if any of the LED’s on the front panel are on. If no
front panel LED's are on, the processor has lost all power. Find
out why immediately. Check if anything else has lost power.
• Disconnectmainstransformerblocks from thewallsocket/outlet.
Re-connect to a different socket/outlet powered by a different
mains circuit.
• If there are now at least two LEDs on, (a projector indicator and
bypass flashing) and sound does come back on, it will be mono
but you can continue the show while you try to find the source of
the trouble.

3-2
• If you know why power was lost and is now back, (there is one or
more LEDs alight in the pushbuttons) check that the format is
appropriate and switch the CP45 out of bypass. The unit will stay
in bypass for about 5 seconds then revert to the format on the
front panel.
• If you don’t know why power was lost keep the unit in bypass
until you can find the reason.
• Be sure that the correct projector and format are selected.
• Check to see if both mains transformer blocks are plugged in
securely to a live outlet.
• If these checks do not restore the sound, and there is at least one
frontpanel LED on,put up thetheatre lights andplay your source
of music. If you are not in bypass, switch to format 60 non-sync
first. If the system operates properly in this format, there is no
problem with the equipment following the CP45 in the system
(such as amplifiers and speakers) and the problem may well be in
the projectors. Double-check both projectors and continue the
show on a working projector if you find that one projector is at
fault.
2. If One Channel Fails or is Distorted
Switch the CP45 to bypass; a mono signal is then fed to all three screen
channels. If the distortion persists in one channel, the power amplifier
or speaker for that channel is probably at fault and the amplifier for that
channel should be switched off for the remainder of the show. If the left
channel has failed, also switch off the amplifier for the right channel, so
that only the center channel is in operation. (If the right channel has
failed, also switch off the amplifier to the left channel.)
If you are showing a mono film and the center channel fails or is
distorted, switch the CP45 to bypass so that the mono signal is fed to the
undistorted left and right channels. In this case, turn off the power
amplifier for the center channel.
3. If Switching to Bypass Does Not Restore Sound
• First, check the exciter lamps, the position of all faders and the
remote mute button. Make certain that all components including
power amps are receiving AC power.
• Turn the fader down.
• CheckthebypassLEDontheCP45;itshouldbeflashing,indicating
that the CP45 switched to the bypass mode. If it is not flashing
and you are absolutely certain that AC power is reaching both the

3-3
CP45transformers, thebypass transformer wiresmust havecome
unscrewed from the back panel connections or, (this is very
unlikely) the transformer has failed internally.
• If you have a spare Cat. No. 514 optical preamp module, switch
off the power amps and processor and replace the Cat. No.514 in
the CP45 with the spare. Switch the power amps back on and
check if sound is restored.
• If replacing the Cat. No.514 does not restore sound in the bypass
mode, the bypass circuitry within the Cat. No.510 circuit card
may have failed. If you have a spare, disconnect power from the
CP45,switchoffthepoweramplifiers,andreplacetheCat.No.510
in the CP45 with the spare. Apply power to the CP45 and turn on
the power amps to see if sound is restored.
4. Excessive or Inappropriate Sound from the Surround Speakers
Asan emergency measure tocontinue the show,switch off the surround
channel amplifiers. At your next opportunity, find out if the problem is
related to the film print itself or the theatre sound system.
• If the film sound was mixed to include surround information, as
are the vast majority of Dolby encoded films, the problem may be
in;
a. The sound system (speakers, power amps), or
b. The alignment of the solar cell in the projector, or
c. The Cat. No.514 optical preamp, or
d. The Cat. No.511 main board decoder section.
Continue the show with the surround amplifiers off and have the
problem corrected later by your service engineer.
B. BETWEEN SHOWS
If the CP45 selected bypass itself and there are no LEDs alight in the
buttons on the front panel. The shows will have to continue in bypass
until the unit can be serviced; however, if manually selected bypass
operation was required to complete a show and your preliminary
checks suggest that the cause of a problem may be a fault within the
CP45, you can take some further steps when you have more time
between shows.