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Film must be mounted on the projector to make adjustments to the BOF and EOF sensors. The film should be positioned
in the projector so that the reflective tape is not in the area of the gate. The sensor adjustment is made based on the
reflectivity of the film, rather than the reflectivity of the tape.
1. Connect an oscilloscope or voltmeter to test point TP7, using TP4 as a ground reference. (See Figure
6.1.) If using an oscilloscope, set it for 1 millisecond per division horizontally and 1.0 volts per
division vertically. Set the trigger to automatic. If using a voltmeter, set the scale to 20 Volts.
2. To adjust the BOF sensor voltage, adjust VR7 for a level of -2.0 Volts.
3. Move the test probe to TP5.
4. To adjust the EOF sensor voltage, adjust VR6 for a level of -2.0 Volts.
5. The trip point for the sensors is at +5 Volts. When the sensors see the reflection from the tape, the
voltage is near +15 Volts, depending on the tape reflectivity.
Reeling System Adjustment
The torque arm position is monitored by an optical potentiometer consisting of an infrared LED and a phototransistor. A
disk with an offset hole is mounted on the torque arm shaft. As the shaft rotates, the disk blocks more or less of the light
beam. The disk is adjusted on the shaft so that the tension arm is at a center position, causing the film to be under tension.
Both mechanical and electrical adjustments may be required. The mechanical procedures apply to both upper and lower
reels, since they are identical in adjustment and operation. The electrical adjustments are carried out using the Reverse
Test Mode command for the projector.
CHRISTIE
CHRISTIE
35/70 Service/PM Manual
March, 1997
TP7
BOF/EOF
R160
6
8
C6
10uF
+
6264
U1
TP4
TP4
J10
1
MOL6LP
39K
TP3
TP2
Figure 6.1: BOF and EOF Adjustments
6 : M e c h a n i c a l a n d E l e c t r o n i c A d j u s t m e n t s
TP5 VR6 VR7
EOF
BOF
J6
EOF
R134
VR6
VR7
1
560K
TP5
R135
5.6K
50K
BOF
U35
1K
R131
LM339
TP7
1K
R130
LS138
U5
U3
6809
2764
U2
6.144MHz
C2
C3
30pF
30pF
Y1
TP1
R192
R44
R126
7.5K
5.6K
560K
R127
TP8
R133
10K
R128
10K
U7
6850
2
1
0
2
K
K
R14
R15
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