Systems Inc., 284 Broadway, Huntington Station, NY 11746 • 631.421.1230 • FAX 631.421.1274
ATD-1200 Dolby Digital/Analog Basement Reader
Test Setup with Oscilloscope
The following test setup will enable adjustment of focus and confirmation and adjustment of LED level and optical alignment.
1. Make sure power to ATD-1200 power supply is provided, Power to the Digital Processor should also be turned on.
2. Open the Digital Processor to gain access to the test points.
3. Connect a probe from Channel 1 of a 20MHz or greater bandwidth oscilloscope to the VIDEO test point of the Video
Acquisition Card, with the ground lead to the VGND.
4. Connect a second probe from the scope’s Channel 2 to the CLAMP signal test point to trigger the scope. Connect the
second probes ground to DGND.
5. Set the trigger source on the scope to Ch.2.
6. Adjust the Ch.2 vertical trace position to move the trace off the screen. It is not necessary to view this signal once
triggering has been established. Adjust the scope for 1 horizontal trace across the screen and adequate vertical gain
(approx. 2 usec
I div. horizontal, 1 V /div. vertical). With SRD film threaded and running in the projector, observe the
video waveform. (see figure 1 in next section)
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Focus Adjustment
The ATD-1200 Readers are factory adjusted and should not require adjustment during installation. If the unit has become
misadjusted focusing may be performed. Using the setup as above, adjust the lens/ CCD assembly in the reader by
loosening the clamp screw located on the upper lens holder assembly, and move the lens assembly back and forth. The best
focus is achieved when the scope pattern has minimum brightness in the center of the trace. There will always be some light
here; one is looking for the most “focused looking” display, with minimum brightness inside the envelope. This should
correlate with a minimum error rate. Re-tighten the lens clamping screw.
figure 1
Adjust for minimum brightness in center of image.
