Dolby Laboratories CP65 manual 222

Page 32

4-10

A-Chain Alignment Procedures

b. Optical Preamplifier Adjustments

	Step	Action	Indication
	No.	Action	Indication
	No.

7

	Lt
Cat. No.
240A
Proj. 1	Rt
GAIN
Lt
hf
GAIN
Rt
hf
Lt tp
Lt
signal
present
Rt
Rt tp
GAIN
Lt
hf
GAIN
Rt
hf	CAT NO.
Proj. 2	CAT NO.
gnd	222
	222

8

✓ ✓

L L

R R

L L

R R

OSCILLOSCOPE TRACES

4-11

A-Chain Alignment Procedures

b. Optical Preamplifier Adjustments

Notes

Thread and play the Dolby tone side of the Cat. No. 69 test film for an initial test of the signal path through the projector preamplifier. The film emulsion should face away from the screen. Adjust the Cat. No. 240A Proj 1 L and R gain potentiometers until the LEDs on the Cat. No. 222 Dual Noise Reduction Module indicate the Dolby level — the center two green LEDs are lit. In addition, verify that the signal present LEDs on the Cat. No. 240A are lit. The Dolby tone signal should be visible on the oscilloscope.

Remove the Cat. No. 69 test film and thread the SMPTE Buzz Track Film. This film has modulation just beyond the normally scanned areas of the optical sound tracks. The objective of this test is to ensure that the slit illuminates only the sound-tracks. Depending on the design of the projector, the positioning of the slit relative to the optical tracks is adjusted as follows:

The film guide is adjusted laterally for a null if the lens and exciter lamp are fixed in position;

The lens and exciter lamp assembly are adjusted laterally for a null if the film cannot be moved laterally.

The adjustment is correct when there is no signal output while the film is played. It may not be possible to adjust for a null with some older slits; in such instances, adjust for a minimum and equal signal on L and R.

Some projectors use a lens with an adjustable slit width. The adjustment is correct at the point when the left and right signals both disappear equally.

Image 32

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 Slot Card Function Cat. No Two-channel NoiseReduction Module 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 Msec Setting Adjustment of Surround DelayThumbwheel Switch 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 +15M Cat. No +24V +15V15V +12B Appendix a Checking Phasing of Speakers Appendix B Effect of Changes in Slit Height on Slit Losses Cat. No a Circuit Description Appendix C CP65M Mono InstructionsOperation Schematic Cat. No a Appendix D Backplane Connections List Terminal Block TB3Connector J18