Service manual

5: Theory of Operation
CHRISTIE INC. - CHRISTIE INC. - 35/70 Service/PM Manual
July, 1997
M
U54A
U53
T
E
2285
Signal
PWM
AMP
U32
Film
Tachometer
Optical Sensor
10
SUMMING
AMP
36
23
Current Limiting
24
U17
25
COMP
Direction
CV Tachometer
To CPU
U34
COMP
ABS VAL
AMP
U54B/U24
Sawtooth
COMP
Figure 5.9: Lower Reel Motor Control Circuit
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.
Signal Type JP1 JP2 JP1 (2293)
Video Sync
1&2 1&2 1&2
External
2&3 2&3 1&2
50/60Hz Line
N/A N/A 1&2
Crystal
4
N/A N/A 2&3
Table 5.10: Sync Separator Card Jumper Settings
4
This setting is not recommended for use with Master/Slave projector configurations.