User`s manual

A-Chain Alignment Procedures
Notes
4-11
b. Optical Preamplifier Adjustments
Thread and play the Cat. No. 69T Dolby Tone 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. 510 Proj 1 L and R gain potentiometers until the LEDs on the
Cat. No. 222SR/A Decoder Module indicate that Dolby level — the center two
green LEDs are lit. In addition, verify that the signal present LED for the center
channel, located on the front panel, is lit. The Dolby tone signal also 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.