Dolby Laboratories CP65 manual Amplifiers, General

Page 42

5-6

B-Chain Alignment Procedures

a. Setting Room Equalization

Step	Action	Indication
No.

5

CONT'D

6

7	NORMAL BYPASS	bypass
		bypass

(switch behind panel)

POWER AMP

ON

5-7

B-Chain Alignment Procedures

a. Setting Room Equalization

Notes

•Check that speakers are correctly connected; that the speaker on the left is really connected to the left power amplifier.

Amplifiers

•Distortion.

•Gross gain differences among amplifiers.

If one amplifier differs in performance from the others, it should be checked and repaired, if necessary, before proceeding further. Input gain controls should all be at the same setting.

•Blown fuses.

Some types of power amplifiers operate at very low gain and distortion even if fuses are blown.

•Good air movement through power amplifiers.

General

If air-conditioning noise is audible in the theatre, arrange for lubrication of the motor, fan bearings, adjustment of belts and drives and cleaning of filters to reduce the ambient noise to a minimum.

Set all the gain controls on all power amplifiers to a known repeatable setting, but do not turn amplifiers on. The preferred setting for the amplifier gain controls is maximum. If a different setting is required in order to optimize the noise performance of the system, the controls should be locked in position or marked clearly.

Position calibrated microphones in the theatre. Whenever possible use multiple microphones and a multiplexer.

For a single microphone the recommended position is shown in the diagram — 2/3 of the way from the front speakers to the rear — but off the axis of the center speaker — 5 feet off the floor level — and angled 45 degrees upward toward the screen. Connect the microphone to the RTA.

Open the front door of the CP65 and ensure that the NORMAL/BYPASS switch is in the BYPASS position.

Turn power ON to the power amplifiers.

Image 42

Contents Model CP65 Cinema Processor Dolby Laboratories Inc Headquarters Table of Contents Section Reference Block Diagrams Introduction Page Section Equipment Required Smpte Buzz Track Stereo Optical Surround Level Cat. No Jiffy Test Film Cat. No 2 Listen . . . Film Cat. NoSection Initial SET-UP and Installation Voltage Acceptable Setting Voltage Range Fuse Type Next, check the jumpers in the following locations Cat. No , Power Supply Module Cat. No , B-Chain CardCat. No , Control Logic Card J2 NON-SYNCCP65 Backplane Standard CP65 or CP65ACP65-300 High Low Subwoofer subwoofer Output output These Modules are Necessary for Bypass Operation Reduction Module Slot Card Function Cat. NoTwo-channel Noise Channel DecoderContains a semi-regulated power supply with Voltage Setting Fuse Type InternationalIEC Notices HUM Problems Room lighting dimmer controls SCR-TYPEPage Section AN Overview of the Alignment Procedure Aligning the B-ChainPage Page Section Chain Alignment Preliminary Procedures Action IndicationLamp Voltage Optical Preamplifier Adjustments Chain Alignment Procedures Optical Preamplifier Adjustments 222 CAT. no Test Film Oscilloscope Traces Repeat CAT no Repeat 1 →Magnetic Preamplifier Adjustments Magnetic Alignment 100mV Section Chain Alignment Setting Room Equalization BypassLoudspeakers and Crossovers Amplifiers GeneralChain Alignment Procedures OffRepeat ActionChain Alignment Procedures Setting Room Equalization Do not adjust Paul Setting Room Equalization b. Adjusting L,C,R Gain 14 → 21 R 14 →Setting Mono Gain 79 dBCChain Alignment Procedures Subwoofer Alignment Cat. No 90 dBC 85 dBCFrom Step NoSelect format 04 Dolby Stereo A-Type Same AS 441Surround Equalization Alignment Cat. No Surround Equalization Alignment Cat. No Notes Cat. No 441Desired 88 dBC Bypass Adjustment of Surround Delay Thumbwheel SwitchMsec Setting Chain Alignment Procedures Adjustment of Bypass Gain Xx dBCFrom Xx dBC -3 dB Yy dBCAdjustment of Non-sync Gain Press the format 60 non sync switchAuto Freq Adjustment of Mono Gain and Equalization Notes Repeat page 5-20 StepChain Alignment Procedures Final Checks Press the format 04 Dolby Stereo A-type switchSection Reference Diagrams Cat. No Dual Noise Reduction Module Inputs Cat. No Optical Bass Extension and Surround Equalizer Card Cat. No B-Chain Facilities Card Cat. No Power Supply Card Cat. No Transformer Module Inputs Cat. No Control Logic Card Cat. No +24V +15V 15V +12B+15M Appendix a Checking Phasing of Speakers Appendix B Effect of Changes in Slit Height on Slit Losses Appendix C CP65M Mono Instructions OperationCat. No a Circuit Description Schematic Cat. No a Appendix D Backplane Connections List Terminal Block TB3Connector J18