Component Engineering STRD-30C User manual

STRD-30C

Digital /Analog Sound Reader

for Century Projectors

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.

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.

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.

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.

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

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.

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.

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.

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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