6-2
dashpot-damped tension arms. The pad rollers on the toothed sprocket are coupled to
allow easy film threading. A spring loaded roller arm damps variations in input film
tension. Bypass rollers are provided to bypass the soundhead with either 35 or 70 mm
film. Figure 6.2 shows Digital Soundhead film path threading. Care must be taken to
thread the film the same way every time, so that the distance from the optical pickup
point to the film gate is constant from show to show. Circuitry in the DA20 processor
delays the signal read at the optical pickup by an amount set during installation. The
threading must match this delay, or improper synchronization will result. NOTE: Film
tension is important. A proper loop is set when the tension arms match the white half
circles. The arms must not touch, or be too far apart (approximately 5mm is correct).
A
C
B
A
C
C
B
B
A
Set film path so that top and bottom tension
arm rollers are approximately 5 MM (1/4 inch) apart.
Use the white painted semi-circles for angular alignment
of tension arms . Make sure that the rollers do not touch.
Digital Print Threading Path
Bypass Threading Path
Figure 6.2 Film threading
6.3
Displays
The DA20 has eight slots in the front panel to allow sets of LEDs to be visible, indicating
the activity of various circuits. The large slot in the center is used as an error rate display
on a seven segment LED. Six of the slots show digital audio signal level, and the last
shows Cinema Processor Status. Each area will be discussed below. See Section 8 for use
of these displays in troubleshooting.
