Dolby Laboratories CP65 manual Magnetic Preamplifier Adjustments Magnetic Alignment

Page 37

4-20

A-Chain Alignment Procedures

c. Magnetic Preamplifier Adjustments

Magnetic Alignment

The CP65 in its normal configuration does not provide noise reduction for signals entering through the Magnetic/Aux input. However an optional configuration using Cat. No. 300 SR/A modules in place of the normal Cat. No. 350 SR modules can be used for playing 70 mm Dolby Stereo prints. To use this option, headers J16, J17 and link J24 on the CP65 backplane must be in the correct position. See page 2-8 for information on the correct positions for J16, J17 and J24.

1.Inspect the magnetic head for evidence of wear. Wear can degrade the frequency response. De-magnetize the head and all elements in the film path, both metal and plastic (some plastic parts may have steel centers). If you have an Annis gauss meter or its equivalent, verify that no elements in the film path are magnetized. Repeat the degaussing, as required.

2.Inspect the penthouse and perform any mechanical adjustments in accordance with the manufacturer’s instructions. Verify that all bearings, gears, and guide rollers are in good working order.

3.Install the magnetic preamplifier according to the manufacturer’s information.

4.Connect the magnetic heads to the MPU input barrier strip with high-quality shielded cable, Belden 8451 or equivalent. Connect the shield at the MPU end only.

5.For a standard CP65 (fitted with Cat. No. 350 SR modules), no A-type noise reduction is provided for magnetic inputs.

•Connect the outputs of the magnetic preamplifier to the

“from mpu - no nr” inputs on the TB3 and TB4 barrier strips. See the wiring diagram on page 2-3.

For a CP65-300(fitted with Cat. No. 300 SR/A modules), A-type noise reduction is provided for L, C,R,S magnetic inputs.

•Connect the outputs of the magnetic preamplifier to the

“from mpu - (format 42)” inputs on TB6 (L,C,R,S) and "fmt 42" input on TB4 (Le, Re). See the wiring diagram on page 2-4.

6.Place the NORMAL/BYPASS switch in the BYPASS position.

Image 37

Contents Model CP65 Cinema Processor Dolby Laboratories Inc Headquarters Table of Contents Section Reference Block Diagrams Introduction Page Section Equipment Required Jiffy Test Film Cat. No 2 Listen . . . Film Cat. No Smpte Buzz Track Stereo Optical Surround Level Cat. NoSection Initial SET-UP and Installation Voltage Acceptable Setting Voltage Range Fuse Type Next, check the jumpers in the following locations Cat. No , B-Chain Card Cat. No , Power Supply ModuleJ2 NON-SYNC Cat. No , Control Logic CardStandard CP65 or CP65A CP65 BackplaneCP65-300 High Low Subwoofer subwoofer Output output These Modules are Necessary for Bypass Operation Two-channel Noise Slot Card Function Cat. NoReduction Module Channel DecoderContains a semi-regulated power supply with International Voltage Setting Fuse TypeIEC Notices Room lighting dimmer controls SCR-TYPE HUM ProblemsPage Aligning the B-Chain Section AN Overview of the Alignment ProcedurePage Page Section Chain Alignment Action Indication Preliminary ProceduresLamp Voltage Optical Preamplifier Adjustments Chain Alignment Procedures Optical Preamplifier Adjustments 222 CAT. no Test Film Oscilloscope Traces Repeat Repeat 1 → CAT noMagnetic Preamplifier Adjustments Magnetic Alignment 100mV Section Chain Alignment Bypass Setting Room EqualizationLoudspeakers and Crossovers General AmplifiersOff Chain Alignment ProceduresAction RepeatChain Alignment Procedures Setting Room Equalization Do not adjust Paul 14 → 21 R 14 → Setting Room Equalization b. Adjusting L,C,R Gain79 dBC Setting Mono GainChain Alignment Procedures Subwoofer Alignment Cat. No 85 dBC 90 dBCStep No FromSelect format 04 Dolby Stereo A-Type 441 Same ASSurround Equalization Alignment Cat. No Cat. No 441 Surround Equalization Alignment Cat. No NotesDesired 88 dBC Bypass Thumbwheel Switch Adjustment of Surround DelayMsec Setting Xx dBC Chain Alignment Procedures Adjustment of Bypass GainXx dBC -3 dB Yy dBC FromPress the format 60 non sync switch Adjustment of Non-sync GainAuto Freq Repeat page 5-20 Step Adjustment of Mono Gain and Equalization NotesPress the format 04 Dolby Stereo A-type switch Chain Alignment Procedures Final ChecksSection 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 15V +12B Cat. No +24V +15V+15M Appendix a Checking Phasing of Speakers Appendix B Effect of Changes in Slit Height on Slit Losses Operation Appendix C CP65M Mono InstructionsCat. No a Circuit Description Schematic Cat. No a Terminal Block TB3 Appendix D Backplane Connections ListConnector J18