3
INSTALLATION & OPERATION
SURROUND CHANNEL TIME DELAY:
The MODIIB has a digital time delay circuit for the surround channel while playing optical stereo prints. Time
delay of the surround channel in optical stereo mode is necessary for two reasons: 1) to mask any front to sur-
round crosstalk and, 2) to synchronize the stage and surround channels to eliminate echo caused by different
sound path lengths from the stage and surround speakers.
MAIN OUTPUTS:
The MODIIB has six output channels: LEFT, CENTER, RIGHT, LEFT SURROUND, RIGHT SURROUND AND
SUB(woofer). The SUB outputs are balanced with SUB+ and SUB- terminals available. This allows a standard
dual channel amplifier to be used in mono bridged mode to feed a subwoofer speaker.
MAIN POWER SUPPLY:
A heavy duty fully-regulated power supply is furnished with the MODIIB processor. This bipolar supply is
heavily filtered and supplies ample current for both the positive and negative 20 VDC supplies. This external
power supply minimizes the chances of hum pickup when high gain electronic circuits are placed in the same
chassis as a power supply. Also, the large power capacity of the supply provides a very “stiff” voltage to all cards
in the MODIIB to prevent power sag (momentary drop of the supply output due to heavy loads). This gives
excellent transient response and superior stability.
EMERGENCY SOUND BACKUP POWER SUPPLY:
A backup power supply is included with the MODIIB to power the backup preamp built into the MODIIB. This
will ensure that you will never lose a show when using the MODIIB processor. The backup supply is located
within the main power supply package and delivers about 15 VDC at 100 mA. The backup capability is a stan-
dard feature on the MODIIB and is not an extra cost option as it is on other systems.
MODULAR CIRCUITRY:
The MODIIB system is housed in a card cage rack mount assembly. All circuitry in the MODIIB is on individual
plug-in cards that allows for easy servicing and future expansion of the system. Each card has its own voltage
regulators that stabilize the circuits locally as well as filter unwanted signals that may be present on the main
power buses.
SECTION 3:
CARD DESCRIPTION
Test points are included on some cards for the sound engineer to access vital circuit points with his scope or
meter. These terminals will accept a meter probe or “alligator” clip. Power must be turned off to the MODIIB
before any attempt is made to remove or install a card. If not, then damage to individual circuit cards may result.
FORMAT CARD:
SRS5x390
Audio format selection, both manual and through automation, is controlled by the Format Card. The different
format changes available are MONO, 3-D MONO, STEREO A (Dolby type A encoded prints), FILM SR (Dolby
type SR encoded prints), DIGITAL and MUSIC. A format is active when the corresponding button is illuminated.
The 3-D Mono feature is active when the 3-D Mono button is lit.
Electrical power to the other cards in the system is distributed through this card. The Format Card is where the
FILM LEVEL fader, MUSIC LEVEL control and REMOTE/LOCAL volume control switches are located. The
NORMAL/BACKUP switch is also located on this card. Flipping this switch to BACKUP gives an emergency
mono center channel. The backup audio level is set by a multi-turn pot on the Mono/Backup Card.
There are two jumpers on the Format Card that select different defaults. Jumper H3 is used to select default opti-
cal selection for digital movies (see DEFAULT OPTICAL SELECTION in the WIRING HOOKUP INSTRUC-
