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The procedure for adjusting the pulldown is given below.
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.
6. When the waveform is correct, monitor the picture for jitter.
7. Tighten the two screws securing the sensor card.
CHRISTIE
CHRISTIE
35/70 Service/PM Manual
March, 1997
Figure 6.4-c: Pulldown Signal Normal Gain
Film must be mounted for this adjustment.
For this adjustment, the sensor card should be moved in a horizontal direction only.
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.
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
Slight change in slope on each
negative-going transition
Pulldown
Signal (TP13)
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