Dolby Laboratories CP500-300 Installation Manual download pdf (Page 32)

A-Chain Alignment Procedures

Step

No.

4-6

IndicationAction

b. Optical Preamplifier Adjustments

Dolby

gnd

Proj. 2

GAIN

Rt tp

Lt tp

Proj. 1

GAIN

signal

present

Cat. No.

240A

A-Chain Alignment Procedures

Notes

4-7

b. Optical Preamplifier Adjustments

Connect the cells to the correct CP65 input terminals via the terminal block, using a single

“twisted pairs” shielded (screened) 4-conductor cable or two shielded 2-conductor cables.

Connect the inner conductors to the projector input + and – terminals exactly as shown.

Connect the shields only at the CP65 end. Note that the cell associated with the right

channel is closest to the edge of the film.

Separate cells are used for each channel in reverse scan projectors. Both use identical

red (high) and black (low) wires. A check will be made in Step 9 to determine the correct

left and right placement.

Loosely install the stereo solar cell bracket on the projector. Position the bracket carefully

until the surface of the cell is 1 mm from the film plane surface. Note that if this distance

is exceeded, there will be crosstalk between the two optical stereo tracks. Check the

image of the slit on the cell. The image should be a thin sharp line. The slit image should

be as long as the cell, and positioned three-quarters of the way up the cell. Try to get

the best compromise among all of these conditions and then tighten the cell bracket

mounting screws.

On the Cat. No. 240A Optical Preamplifier Card

Turn all of the Proj 1 and Proj 2 gain potentiometers fully clockwise (CW).

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Dolby Laboratories CP500-300 Installation Manual Page 32