THE MICHAEL TODD COMPANY, INC.
ENGINEERING BULLETIN #9
4th TRACK INTEGRATOR CONTROL FOR SURROUND SOUND EFFECTS
MODIFICATION DATA PERSPECTA SOUND INTEGRATOR UNIT
(FOR "AROUND THE WORLD IN EIGHTY DAYS"
SURROUND SPEAKER OPERATION)
When the 30-35-40 cycle control signals are not present in the input to the standard Perspecta Sound Integrator unit, a relay ("fail-safe" or "auto-switching") attenuates the integrator left and right amplifier circuits, leaving the center amplifier circuit with fixed normal gain.
This control circuit must be modified to keep the left-center-right amplifier circuits normal (Perspecta Sound), with their output levels directly controlled by the amplitudes of the 30-35-40 cycle control signals.
After modification the Integrator Unit switch "Perspecta Sound-off/auto", will control operation as follows- "Auto" operation will be "Perspecta Sound" as in the preceding paragraph. "Off" will be normal, non-Perspecta, surround speaker operation with the left center-right speaker groups operating simultaneously at the normal fixed level distribution.
Circuit Changes - (Fairchild units - Drawing #G 21407)
(1) Lift C 22, 0.1 mfd. grid coupling condenser of V 3, off control circuits R 30-31-32 and connect to one side of heatre circuit at any tube socket.
(2) At "auto" relay RL1, lift off leads on normals of left and right circuits (-20 v. bias), solder leads together and tape. Strap together the normals of the left-center-right circuit sections of the relay.
(3) With switch SW1 open ("auto"), relay operates to contacts and unit is operating "Perspecta". Adjust R29 - "Auto switching sensitivity" to operate relay. (Time delay operation) Do not operate R 29 at maximum.
(4) With switch SW1 closed ("off") relay RL1 is on its normals and the equal level in the three output circuits may be adjusted at R5 ("Mono Gain") in the Integrator power unit.