		  Digital Soundhead Alignment
		  ------- --------- ---------

		  Digital Soundhead Mechanical Alignment
		  --------------------------------------

Mechanical alignment of the Dolby Digital Soundhead consists of making sure the
film path through the Digital Soundhead is aligned with the path through the 
rest of the projector.

1.     Thread a length of film 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.

Alignment for the basement reader varies with the projector and basement reader 
type.  Generally, little mechanical adjustment is necessary, but the optical and 
other adjustments described below may be necessary.


		  Test Setup with Oscilloscope
		  ---- ----- ---- ------------

The following test setup will enable adjustment of focus and confirmation and 
adjustment of lamp level and optical alignment.

1.      Make sure power to the DA10/20 or CP500 and to the Digital Soundhead is
	    provided.

2.      Remove the DA10/20 front panel.  If a CP500 is used, open the door.

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 in slot 12 of the DA20(leftmost card), with the 
	    ground lead attached to VGND (TP2, just below TP1).  If you have a 
	    DA10, connect a probe from Channel 1 of the scope to the VIDEO Test 
	    Point (TP5) on the Cat. No. 605A Video Acquisition Card in slot 2 of 
	    the DA10.  (Slot 1 is empty)  With a CP500, use DA20 instructions.

4.      Connect a second probe from the scopes Channel 2 to the CLAMP signal 
	    test point (TP3 on DA20; TP4 on DA10) to trigger the scope.  
	    Connect the second probes ground wire to DGND (TP7 on DA20, TP10 on 
	    DA10).

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 after triggering 
	    has been established.

Adjust the scope for 1 horizontal trace across the screen, and adequate vertical 
gain (approx. 2 microsec/div. horizontal, 1 V/div. vertical).  With SRoD film 
threaded and running in the projector, observe the video waveform.


		  Focus Adjustment
		  ----- ----------

Cat. No. 700 and 699 Digital Soundheads are factory adjusted and should not 
require adjustment during installation.  If the soundhead has become 
misadjusted, focusing may be performed.  Using the scope setup as above, adjust 
the objective lens/CCD assembly in the reader head by loosening the 2mm hex 
socket set screw (located below the lens bore) which holds the lens/CCD 
assembly in place, and moving the assembly back and forth.  On a Cat. No. 700, 
a flat blade screw driver inserted in the oval slot above the lens can be 
twisted to slide the assembly.  Alternately, if the CCD circuit board cover is 
removed, the assembly can be moved back and forth with the thumb and forefinger.  
With basement readers, the adjustment method varies, but most readers move the 
lens to focus.  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 minimum error rate.  Another 
method is to maximize the number in the focus window of the DRAS program.  This 
method is usually a lot slower than using the scope method, but may be more 
accurate.  After focusing, re-tighten the lens holding screw.    


		  Exciter Lamp Level Confirmation and Adjustment
		  ------- ---- ----- ------------ --- ----------

On a Cat. No. 700/699, the output voltage of the lamp power supply is factory-
set to be between 9.5 and 10 volts.  Lamp intensity has a direct relationship 
to the video signal voltage.  The acceptable range for the peak video signal 
voltage (of unobstructed light through the perf hole) is between 2.7 and 5 
volts.  Under normal circumstances, the lamp power supply voltage will never 
need adjustment to achieve the acceptable video voltage range.  However, some 
combinations of individual lamp intensity and projector speed may result in a 
video signal outside the 2.7 to 5 volt range.  In that case,  it may be 
necessary to adjust the lamp power supply.  Do not adjust voltage above 10 
volts at output of power supply for a Cat. No. 700.  For a Cat. No. 699, 
adjustment to 12 Volts can be made. 

There are several varieties of basement readers, some use lamps, and some use 
Red LEDs.  The user should refer to the instructions for their basement reader 
for instructions on adjusting lamp/led current.  In any case, the proper video 
level is 4 Volts.  The DA20/10 does not send any information to the computer on 
video level, so therefore, this adjustment MUST be done with the scope.

If the top of the video waveform is not reasonably flat (+/- 1 division), check for 
dirt, dust, or other obstruction to the light path, and clean.  



		  Film Path Alignment
		  ---- ---- ---------

The film path of a Cat. No. 700/699 is aligned during manufacture and should not 
require adjustment during installation.  The procedure for confirming or 
adjusting the film path follows.
 
The flanged guide roller on the top tension arm (the spring loaded roller 
between the sprocket and drum) is the only film guide with provision for 
lateral adjustment.  The specification for its position is based on nominal film 
position.  The film should be guided so that the inner edge of the film is 
25.4mm (+0.1-0.1mm) from a machined reference surface on the soundhead housing 
(19mm diameter unpainted spot between the sprocket boss and the light pipe).  
The outer edge of the flange on the guide roller therefore should measure 
61.9mm from the reference surface.  To adjust the position of the guide on a 
DA20, the rear panel of the soundhead, the flywheel, and the tension arm spring 
must be removed.  Before loosening the clamp screw, note the angular position of 
the spring arm with respect to the tension arm on the front of the soundhead 
(return the arm to the same angular relationship prior to tightening).  The 
lateral adjustment screw can be turned after the clamp screw is loosened.  A 
quarter turn of the adjusting screw will move the lateral guide roller 
approximately  0.1mm.

The film path of a basement reader should be adjusted according to the 
instructions provided by the manufacturer.


		  Optical Alignment
		  ------- ---------

The soundhead is optically aligned at manufacture and should not require 
adjustment unless the CCD circuit board has been moved or replaced (the CCD 
sensor is located on the CCD circuit board.  Optical alignment of the sensor 
depends on the position of the circuit board).  Two adjustments of CCD board 
position are possible: lateral and rotational (azimuth).  The procedure for 
confirming or adjusting the position of the CCD board follows.

Lateral position can be confirmed if the video signal (of unobstructed light 
through the perf hole) on the oscilloscope falls 0.2 div. left of center of the 
total CCD video signal.  To center the video signal on the scope do the 
following:

1.     Use the scope setup described in 4.2 above, observe both channel 1 and 

2.     Run SRoD film through soundhead.

3.     Using uncalibrated time base, the scope image should be adjusted so that 
	   the falling edge of the clamp signal is at the first scope graticule, and the 
	   rising edge of the clamp is at the last scope graticule.

4.     If the CCD circuit board is aligned, the video signal of light through 
       the perf hole will be centered (left of center by 0.2 div.) between the 
       falling edge of clamp (trigger) trace and the rising edge of clamp trace.  
       To check alignment with the DRAS program, thread a loop with a known 
       lateral block placement (such as a Cat. No. 530), and adjust lateral 
       position so that the number in the lateral position window matches the 
       film.

5.     To re-align the CCD board, first loosen the two lateral adjustment screws 
	   shown in the diagram of the circuit board.  Move the board laterally 
	   while observing the image on the scope.  When the video trace is 
	   centered with respect to the clamp trace, or the lateral block 
	   placement reported by the DRAS matches the film, tighten the screws. 
	   Many basement readers have a separate adjustment for CCD placement.  
	   See the instruction manual for your reader.
		 

The azimuth adjustment controls the angular position of the CCD board with 
respect to the film.  To adjust the azimuth of the CCD:

1.     On a Cat. No. 700, loosen the two azimuth adjustment screws.  The focus 
	   adjustment screw will also need loosening slightly.  Basement 
	   readers have different methods for adjusting azimuth.  See 
	   instructions from manufacturer.

2.     Rotate the CCD circuit board assembly clockwise and counterclockwise 
	   and observe the azimuth window in the DRAS program.  Adjust for 0 
	   azimuth.
