7 : T r o u b l e s h o o t i n g G u i d e
CHRISTIE INC.
CHRISTIE INC. -
- 35/70 Service/PM Manual
July, 1997
Image Quality Checklist and Diagnostic Table
This procedure requires the lamp house to be on with suitable lens and screen setup.
Perform the checklist in Table 7.13. Refer to the associated diagnostic table, Table 7.14, for corrective action.
IMAGE QUALITY CHECKLIST
Push the <FOR> button and after film speed stabilizes enter the <C>,<3> command
to cause the douser to open.
Checklist
Item
Step Description
Completed
Verify that the projected picture does not have excessive jitter, side
weave, or ghosting.
Table 7.13: Image Quality Checklist
IMAGE QUALITY DIAGNOSTIC TABLE
1
Poor Image Quality –
CONDITION 1: Frame line jumps in and out of picture area on the screen, resulting
in jitter one perf high. This condition is the result of a missing pulldown index pulse
or one that comes at the wrong time due to mis-adjustment of the pulldown sensor.
Step
Diagnostic
Result
1
Verify index pulse at U10, pin 11, of the 2293 card. Connect
oscilloscope to this point. Move pulldown sprocket at least one quarter
turn to produce one high-going pulse. If pulse is not present, trace to
the 2276 card and finally to the pulldown sensor to determine failure
point. Repair wiring fault or replace 2276 card or 2268 card, as
required.
2
If the pulse is present, connect dual trace oscilloscope to TP13 of the
2293 card and pin 11 of U10, also on the 2293 card. The signal at
TP13 is the analog registration error signal; the signal at U10 is the
index signal. Rotate the pulldown sprocket clockwise. Note that the
analog signal moves b10 volts and -10 volts five times for
every index pulse. Rotate the pulldown sprocket clockwise until just
before the index pulse goes positive (0- to +5-volt signal). Verify that,
as the sprocket continues in a clockwise direction, the index pulse is
high at least from the time the analog voltage goes from +5 volts to -5
volts. This is required so that the CPU can determine if the projector is
in frame; otherwise it will do 4-perf and then 6-perf pulldowns, trying
to bring the picture in frame. If necessary, recalibrate the pulldown
sensor assembly, the 2268 card. (See Section 6.5.)
3
This condition can also occur due to worn brushes on the pulldown
motor. Replace brushes or motor assembly as required.
Table 7.14: Image Quality Diagnostic Table
