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10
To CPU
CV Tachometer
The lower reel motor controls summing amplifier U54A. The absolute-value circuit is formed by U54B and U24; the
PWM conversion is done by U53. U17 determines the polarity and outputs a direction signal to the lower torque power
amplifier. The current-limiting signal from the power amplifier turns on the photocoupler, U45, which limits the voltage
sent to the pulse width modulator, U53. The Optical Sensor is monitored using comparator U34. Transistor Q10 disables
the PWM output in the Platter mode of operation.
The Sync Separator Card (0300)
The Sync Separator card (see Section 8.2) is used to extract vertical sync timing information from a composite NTSC,
PAL, or SECAM video input signal. This card is also used to select the type of reference signal being supplied to the
projector. The jumper settings on the board control 50/60Hz line frequency, external 60Hz, vertical video
synchronization, and internal synchronization (See Table 5.10). When operating the 35/70 projector in the Master/Slave
mode it is important the both projectors are receiving their sync from the same source.
4
This setting is not recommended for use with Master/Slave projector configurations.
CHRISTIE INC. - 35/70 Service/PM Manual
CHRISTIE INC. -
July, 1997
U34
Optical Sensor
COMP
U32
SUMMING
AMP
AMP
Figure 5.9: Lower Reel Motor Control Circuit
Signal Type
Video Sync
External
50/60Hz Line
4
Crystal
Table 5.10: Sync Separator Card Jumper Settings
Tachometer
ABS VAL
AMP
U54A
U54B/U24
36
23
Sawtooth
U17
COMP
JP1
JP2
1&2
1&2
2&3
2&3
N/A
N/A
N/A
N/A
5 : T h e o r y o f O p e r a t i o n
E
T
Current Limiting
U53
PWM
Signal
2285
24
COMP
Direction
25
JP1 (2293)
1&2
1&2
1&2
2&3
Film
M
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