Component Engineering STRD-30C User manual

Copyright ©Component Engineering, All Rights Reserved
STRD-30C
Digital /Analog Sound Reader
for Century Projectors

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STRD-30C
Analog and digital sound pre-amps
Digital/Analog Sound Reader for Century Projectors
Installation Instructions
The following installation instructions assume that all conventional
sound track reading elements have been removed from the sound
head. These include the exciter lamp and its socket assembly, the
slit lens with its mounting bracket, and the entire photocell
assembly. The sound drum (rotary stabilizer) and its ball bearings
must also be removed temporarily.
NOTE: The analog and digital sound pre-amps and their optics
are shipped already installed in the dual lens mount. This assembly
has been pre-aligned in a standard Century R-3 sound head. You
are strongly urged to leave it as a unit so that when you are ready
to do the final alignment of the sound head, focus and azimuth will
be very close to their final positions.

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Assemble the locator plate and adaptor block
Insert the screws loosely
Use the bearing to center the assembly
As you begin the installation please refer to the drawings on the
left. Assemble the locator plate and adaptor block by slipping the 2
holes in the locator plate over the 2 pins in the adaptor block.
Position the locator plate’s large hole over the sound drum’s ball
bearing seat and hold in place with three 8-32 x 1/2" screws
through the holes on the right side of the plate. Do not tighten
these screws.
The three mounting holes in the adapter block will now be over the
tapped holes originally used to mount the slit lens holder in the
casting. Install the three 8-32 X 1/2" screws but do not tighten.
The reason for all this loose mounting is so that we can get all of
the optical pieces properly aligned exactly on radius with
reference to the center line of the sound drum. You are going to
use the outboard sound drum bearing to accurately position the
locator plate, and then all the other parts will automatically be
aligned. The idea is to slide the bearing through the large hole in
the locator plate and still be part way into the bearing seat. With
the bearing partly in the plate and partly in the bearing seat, the
plate will be positioned exactly on center with respect to the sound
drum.
Now you can tighten the three screws which hold the plate, the
three screws in the adapter block, and begin reinstalling the sound
drum and flywheel. Remove the rear bearing, discard the spring
washer that is behind it and reinstall the bearing. Now you can
install the scanning drum. Insert the wave washer provided in the
kit between the rear bearing and the locking collar. Compress the
washer lightly and lock down the collar.

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Attach LED assemblies to the standoff
Dual lens/pre-amp assembly
Attach the Airpot to the locator plate
The LED assembly can now be mounted to the top of the standoff
post by means of two 4-40 Flat Head screws.
The dual lens/pre-amp assembly should now be carefully eased
onto the dowel pins in the adapter block and bolted in place. It is a
good idea to have the digital video cable already plugged onto the
digital pre-amp circuit board before you mount this assembly.
Attach the plunger of the AirPot to the standoff on the locator
plate. Leave the nylok screw loose enough so it will not bind the
plunger.

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Analog pre-amp
Wiring
Connect both of the LEDs to the outputs of the LS-30 power
supply chassis. The small terminal strips at the rear of the LED
assembly can be unplugged by pushing away from you. Note that
no polarity is indicated. This is because the LEDs may come with
either polarity and you will have to determine the correct
connection by trial and error. It is safe to do this because the
output of the LS-30 power supplies is clamped at a voltage too low
to damage the LEDs. The recommended wire size is #18 AWG.
The analog pre-amp is powered by the 12 Volt bipolar supply in
the LS-30 and three conductor 22 Gauge wire is perfectly adequate
for this purpose.
The analog audio output from the pre-amp should be two shielded
pairs, one for each channel. They can be individual cables, or two
pairs in one jacket. Normal audio wire such as you would use for
any other purpose is ideal.
All of the terminal strips on the analog pre-amp can be unplugged
at the pre-amp.

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Adjustment of the two light sources
Adjust the analog LED
The video output cable from the digital pre-amp in the sound
head to the Dolby DA-10 or DA-20 is harder to deal with because
it is so stiff and heavy. The cables are shipped with both ends
terminated in their respective connectors. The smaller connector
(the sound head end) can be gotten through 3/4" conduit, but care
must be taken if there are many bends and particularly when going
through any conduit fittings. The connector is polarized and will
plug onto the video pre-amp only one way.
Alignment
Preliminary:
Because you are dealing with two soundtracks, and because you
are starting from scratch, you will have to go back and forth
between the two media while you get everything optimized.
Mostly, this means the adjustment of the two light sources. The
good news is that as already mentioned, the two optical assemblies
have been preset so that you have a beginning point. Their focus
and azimuth may not be exactly correct for your sound head, but
they will be close enough to get you started. Loosen the clamp
screw of both of the copper LED mounts until they can be moved
easily, but will stay where you put them when you let go. It is
easier to grab both of the mounts when doing the analog LED
(which is the inner one), and so it is best to do it first.
Analog:
Adjust the analog LED by eye until it looks as though it is
opposite the lower lens. In the cinema processor, turn both the
level and high frequency adjustments all the way down so that
both channels will be essentially identical. Thread a loop of Dolby
Cat. No. 97 (a very convenient method is to make a loop of 1/2
Cat. No. 97, and 1/2 “Buzz Track”) and look at it on your
oscilloscope just as you would for a normal “A” Chain setup.
Digital pre-amp

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Adjust the lateral guide roller
Analog focus and azimuth alignment
Adjust the lateral guide roller until you have agreement between
both the Cat. No. 97 and the “Buzz Track”. Adjust the lateral
position of the LED for maximum output from both channels. The
lateral guide position is important because it also establishes the
correct position for reading the digital track.
Move the LED in and out and vertically (rotationally) until you
have achieved the maximum output from both channels. Gently
tighten the clamp screw of the analog mount. Try not to overdo the
screw tightening so that the threads in the soft copper are not
deformed. There is a large area of contact between the copper
mount and the round stud on the support plate which means that it
takes only modest clamping pressure to firmly hold the
adjustment. (The other reason for this large contact area is that
there is very good heat transfer from the LED itself right on down
to the base casting of the sound head. This means extra long life
for the LED.)
Now is the time to do the rest of the analog focus and azimuth
alignment procedures. Before you do your final Dolby Tone level
adjustment, it is a good idea to run Dolby Cat. No.566 scanning
beam illumination film. Touch up the in-and-out adjustment of the
LED if necessary.
If you are sure that your vertical, or rotational, adjustment is nearly
correct, there is an interesting method of optimizing it. Remove all
film from the projector and turn on the motor. Monitor the sound
from the reader and turn the gain up until you hear the slight
microphonics from the running projector. Tweak ever so carefully
the vertical position of the LED until the least sound is heard. This
will be the optimum position of the LED Lock the clamp screw,
set your Dolby Tone level and move on to the digital.

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Screen snapshot of DRAS 10 software reading a loop of Dolby Digital test film
(note the recurring splice Error History).
Digital:
Connect your ’scope to Dolby’s digital processor (DA-10, DA-20, or CP500) according to their instructions, and start
running some digital film. The following are optional but highly recommended: A 486 class or better computer having a
high-speed (115kbs.) serial port and DRAS-10 software from Dolby. A nine conductor male to female cable with standard
9 pin “D” connectors that are wired pin to pin. It is possible to perform a good alignment using test film and an
oscilloscope, or it is possible to use test film and a computer running Dolby's DRAS-10 software.

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Adjust the digital LED
Best of all, however, is to use both at the same time. The ’scope
will show you the real-time video of what the reader is “seeing” on
the soundtrack, while the computer will numerically display,
focus, azimuth, vertical jitter, lateral alignment and more. Taken
all together, proper alignment is quick, easy, and accurate. (If you
are running loops, try to make them fairly long so that the splice
doesn’t come around too often). The digital reader optics should be
close enough for you to find a ‘scope picture similar to this
illustration.
The first thing is to adjust the digital LED. You want the
brightest and most even light you can get. This will be indicated on
the ‘scope screen by the flattest trace with the greatest amplitude.
Now that you have adjusted the analog LED, you know the routine
except that this time you will be working with the outer LED only.
Be careful not to loosen the analog LED mount so that you won’t
have to do all that work over again.

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CCD board lateral adjustment
Loosen the CCD board lateral adjustment locking screws and
adjust the lateral position so that outer trace (perf) is off center by
1/5 major graticule to the left between goal posts. A correct DRAS
“lateral position” read out should be as close to zero as possible.
As you retighten the screws be careful not to walk the board in the
reader.

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We are ready to adjust the focus and azimuth of the digital
optics. Because the optics have been preset, there is always the
chance that focus may be OK. Adjusting focus and azimuth are
similar for digital and analog. The reader clamp is loosened and
the reader is moved forward or back to adjust focus. When using
the ‘scope a correct digital burst, the “Grass”, will be in good
focus and the center area will be somewhat darker, exhibiting
“hollowness”. Using DRAS you are looking for the highest
“focus” number. Expect to achieve high 60s to 70s with our reader.
Azimuth adjustment is difficult when using only a ‘scope. Rotate
the reader to adjust for the flattest perf trace and the lowest error
rate on the processor display. Large azimuth errors are seen as a
tipping of the ‘scope sprocket hole trace. The axis will be the
center of the displayed perf trace. The DRAS azimuth number you
are looking for is as close to zero as possible. Retighten the clamp
screw when both focus and azimuth have been optimized.
Final:
Analog:
You are ready to go back and double-check the analog setup. Start
as you did before by checking lateral position. It should not have
changed, but if it has, it is OK to refine it. Make sure your Dolby
Tone, equalization, scanning beam illumination and lateral guide
are still correct.
Digital:
The last step is to fine adjust the rotation of the digital LED to
minimize the unevenness of the sprocket hole trace. Now run a
piece of film with a good sound track and go sit in the theater and
“test” some really fine sound.

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