
Dolby Digital 
Reader Alignment Instructions



Set up the scope...

Set the probes to the X1 position and not the X10 position.
Set volts per division of both channels 1 and 2 to 1 volt/div.
Set time per division (horizontal sweep) to 2 micro sec/div. 
Set channel 1 variable vernier to it's locked or calibrate position.
Set your seat backs and tray tables to their upright and locked positions.
Set trigger source to channel 2.
Set polarity or slope to positive.
Set view mode to ALT (alternate) to view both channels.
	
Calibrate scope to processor...
	
Connect Channel 1 probe to Video test point (White) on Cat. No. 670 card.
Connect Channel 1 probe ground to Video Gnd test point (Black) on Cat. No. 670 card.
Connect Channel 2 probe to Clamp test point (Green) on Cat. No. 670 card.
Connect Channel 2 probe ground to DGND (digital ground) test point (Black) on Cat. No.670 card.
	
Thread and run a loop of Cat. No. 69P or 69T in projector and reader.
Adjust the oscilloscope's trigger level control until it locks on signal.
Adjust the horizontal left/right position to line up the inside edge of the left clamp signal
    with the furthermost left graticle.
Unlock and adjust the variable sweep vernier (time per division) to line up the inside
    edge of the right clamp signal with the furthermost right graticle.

Alignment of Digital Reader...

You should now see the left and right clamp signals, the film perforation (outer envelope)
    and the digital data (block inside the perf envelope).
Adjust the reader's lateral position such that the left and right perf edges (outer envelope) are 
    centered between the clamp signals (ignore the digital data block position). 
    This adjustment is approximate and will be repeated at the end.
Adjust the light source for the best displayed maximum video amplitude (between 2 - 5 Volts)
    measured from baseline trace to upper perf trace... while at the same time adjusting 
    for best overall flatness (+/- .5 Volt) and minimum ripple across this upper perf trace.
Adjust azimuth for all Cat. No. 671 LED's to be lit and minimum error display reading.
    If available, use DRAS10 to adjust for zero reading.
Adjust lens tube for best focus of the digital data block such that the scope image appears
    more "in focus" and darker in the center region rather than the top and bottom edges.
    If available, confirm highest reading with DRAS10.
To fine-tune the lateral position, adjust the perf to be slightly offset to the left by one minor 
    (not major) graticle division or 2/10 to the left of center.
			
