Dolby Laboratories CP65 - Manual (Page 37)

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.
A-Chain Alignment Procedures
4-20