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
CHRISTIE
CHRISTIE
35/70 Service/PM Manual
March, 1997
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.
TP5 VR6 VR7
TP7
BOF/EOF
J6
EOF
BOF
EOF
BOF
U35
U7
U3
U2
U1
J10
TP4
MOL6LP
TP2
TP3
39K
1
R192
TP4
C3
C2
TP1
30pF
30pF
Y1
6.144MHz
R15
R14
1
6850
6809
10K
10K
R128
R133
LM339
1K
1K
TP8
7.5K
R44
R127
R126
5.6K
560K
560K
R134
R135
5.6K
50K
1
TP7
TP5
VR6
VR7
R131
R130
6
8
0
K
K
2
2
R160
C6
10uF
+
U5
LS138
2764
6264
Figure 6.1: BOF and EOF Adjustments
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.