Dolby Laboratories CP500-300 Specifications download pdf (Page 67)

7-3

7.4 Exciter Lamp Level Confirmation and Adjustment

The output voltage of the lamp power supply is factory-set to be between 9.5 and

10 volts (See scope set up in Section 7.2). Lamp intensity has a direct relationship

to the video signal voltage. The acceptable range for the peak video signal voltage

(of unobstructed light through the perf hole) is between 2.7 and 5 volts (see figure

above). Under normal circumstances, the lamp power supply voltage will never

need adjustment to achieve the acceptable video voltage range. However, some

combinations of individual lamp intensity and projector speed may result in a video

signal outside the 2.7 to 5 volt range. In that case, it may be necessary to adjust the

lamp power supply. See the figure below (7-2) for the adjustment location (VR1).

Do not adjust the power supply output voltage above 10 volts.

If the top of the video waveform is not reasonably flat (±1 division), check for dirt,

dust, or other obstruction to the light path, and clean (see Section 7.8).

[VR1]

Voltage Adjust

Figure 7- 2.

Adjustment location for lamp power supply.

7.5 Film Path Alignment

The film path is aligned during manufacture and should not require adjustment

during installation. The procedure for confirming or adjusting the film path follows.

The flanged guide roller on the top tension arm (the spring loaded roller between

the sprocket and drum) is the only film guide with provision for lateral adjustment.

The specification for its position is based on nominal film position. The film should

be guided so that the inner edge of the film is 25.4mm (+0.1-0.1mm) from a

machined reference surface on the soundhead housing (unpainted area between the

sprocket boss and the light pipe). The outer edge of the flange on the guide roller

therefore should measure 61.9mm from the reference surface. To adjust the position

of the guide, the rear panel of the soundhead, the flywheel, and the tension arm

spring must be removed. See Figure 7-3 for the location of the two screws that

control the position of the roller. Before loosening the clamp screw, note the

angular position of the spring arm with respect to the tension arm on the front of

the soundhead (return the arm to the same angular relationship prior to tightening).

The lateral adjustment screw can be turned after the clamp screw is loosened. A

quarter turn of the adjusting screw will move the lateral guide roller approximately

0.1mm.

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Dolby Laboratories CP500-300 Specifications Page 67