Dolby Laboratories CP500-300 Specifications download pdf (Page 65)

SECTION 7

THE CP500 DIGITAL SYSTEM

7.1 Mechanical Alignment

Mechanical alignment of the Cat. No. 700 Digital Soundhead consists of making

sure the film path through the Digital Soundhead is aligned with the path through

the rest of the projector. For built-in (basement) digital soundheads, see the

manufacturer's instructions.

1. Thread a length of film from a supply reel through the Digital Soundhead (refer

to the threading diagram located on the soundhead), and on through the

projector as you would any film.

2. Apply tension to the film and inspect for equal tension on both edges of the film.

3. Check for uneven forces on the rollers, or twisting of the film.

4. When the path is aligned, tighten the soundhead mounting bolts and reel arm.

7.2 Adjustment Setup with Oscilloscope

NOTE

: The Dolby Cat. No. 700 Soundhead is optically aligned at manufacturer and should not require

adjustment unless the CCD Circuit Board has been disturbed.

The following test setup will enable adjustment of focus and confirmation and

adjustment of lamp level and optical alignment.

1. Make sure power to Cat. No. 700 Digital Soundhead is provided. Power to the

CP500 should also be on.

2. Open the CP500 front panel.

3. Connect a probe from Channel 1 of a 20MHz or greater bandwidth oscilloscope

to the VIDEO Test Point (TP1) on the Cat. No. 670 Video Acquisition Card

with the ground lead attached to VGND (TP2, just below TP1). See the fold-

out drawing located at the end of Section 3 for the card location.

4. Connect a second probe from the scope’s Channel 2 to the CLAMP signal test

point (TP3) to trigger the scope. Connect the second probe’s ground wire to

DGND (TP7).

5. Set the trigger source on the scope to Channel 2.

6. Adjust the Channel 2 vertical trace position to move the trace off the screen. It

is not necessary to view this signal once triggering has been established.

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Dolby Laboratories CP500-300 Specifications Page 65