Service manual

6: Mechanical and Electronic Adjustments
CHRISTIECHRISTIE 35/70 Service/PM Manual
March, 1997
Pulldown
Signal (TP13)
Slight change in slope on each
negative-going transition
Figure 6.4-c: Pulldown Signal Normal Gain
The procedure for adjusting the pulldown is given below.
Film must be mounted for this adjustment.
1. Connect an oscilloscope to test point TP13 on the CPU/Main Logic card, card 2293. (See Figure
6.5.) Set the vertical deflection to 5.0 volts per division, and the horizontal to 2 milliseconds per
division.
2. Apply power to the lamphouse, strike the lamp, and power the projector. Enter a READY
command (hit the READY key).
3. Slightly loosen the two screws securing the pulldown sensor card.
4. Enter a FORWARD command (the <FOR> key), and monitor the waveform on the scope.
5. If the waveform is as shown in Figure 6.4-a or 6.4-b, move the sensor card until the waveform
more closely matches the one shown in Figure 6.4-c.
For this adjustment, the sensor card should be moved in a horizontal direction only.
6. When the waveform is correct, monitor the picture for jitter.
You may have to fine-tune the adjustment to minimize the jitter. The resultant scope
waveform may not conform exactly to the waveform shown in Figure 6.4-c.
7. Tighten the two screws securing the sensor card.