RCA 76-B2 User manual

RCA Consolette
Type 76-B2
(MI -11613-B)
Type 76-B4
(MI -11613-C)
Power Supply
(MI -11301-B)
RADIO CORPORATIOn OF AIflERICA
RCA VICTOR Division CAMDErl, fl. J.
1B-24454

BROADCAST EQUIPMENT
INSTRUCTIONS
RCA Consolette
Type 76-B2
(MI -11613-B)
Type 76-B4
(MI -11613-C)
Power Supply
(MI -11301-B)
RADIO CORPOR ATIOrl OF A MERICF1
RCA VICTOR Division CAMDE11, 11. J.
PRINTF'D IN U. S. A.
4136

Table of Contents
Page Page
Part I Installation Override Switch 16
Emergency Program Channel 16
Technical Data iii Emergency "B" Supply 17
Description 1Relay Operation 17
Speaker Relay Interlock 17
Associated Equipment 2Light Relay Interlock 17
Microphones 2Speaker Relay Interlock (Two or Three Studio
Microphone Stands 2Operation) 19
Transcription Turntables 2Light Relay Interlock (Two or Three Studio
Recorders 2Operation) 19
Recording Amplifiers 2Speaker Relay Interlock (Single Studio Operation) 20
Loudspeakers 2Light Relay Interlock (Single Studio Operation). 20
Signal Lights and Relays 4Suggested Operating Procedure 20
Power Supply 4To Place a Program on the Air 20
Conduit Terminating Box 4To Audition Studio B while Studio A is on the Air.. 21
6 db Pad for Telephone Lines 4To Cue Studio B from Studio A and then place
BR -84 Rack or MI -11500 Wall Box 4Studio B on the Air 21
Radiotrons 4To Cue Studio B from a Cue Line and then place
Wall and Floor Outlets 4Studio B on the Air 21
Locating and Connecting Equipment 7To Talk Back to Studio A or Studio B 21
Connections to 76-B2 and 76-B4 Consolettes 7Announcing 21
Audio Input Connections 8Emergency Use of Monitor Amplifier 21
Audio Output Connections 8Network Monitoring 21
Connecting Associated Equipment 9
Addition of Signal Lights 9Part III-MI-11301-B Power Supply
Studio "On Air" and "On Audition" Signal Lights 9
Control Room On Air Relay 10 Technical Data 25
Announce Booth Speaker and Signal Light Relays 10
Console Signal Lights 10 Description 25
Instantaneous Recorder 10 Installation 26
Mounting 26
Conduit List for Types 76-B2 and 76-B4 Connections 26
Consolettes 11 Loudspeaker Field Supply 26
Emergency Switch 26
Part II-Operation Hum Adjustment 27
General 15
Program Channel 15 Part IV Maintenance
Audition Channel 16
a. Monitoring 16 Inspection and Checking 31
b. Auditioning 16 Care of Pushbutton Switches 32
c. Cueing 16 Care of Key Switches 32
d. Talk -Back 16 Voltage Measurements 32
Remote Line Cue and Phone 16 Replacement Parts 33
a. Cue 16
b. Phone 16 List of Parts 33

ii
List of Illustrations
Page
Figure 1-Type 76-62 Consolette with Door Open 1
Figure 2-Type 76-62 Consolette with Chassis Raised 3
Figure 3-6 db Pad for Telephone Lines 4
Figure 4-Suggested Recording Setups 5
Figure 5-Front Panel Layout .5
Figure 6-Relay Mounting Cabinet 6
Figure 7-Installation Diagram 6
Figure 8-Mounting Dimensions 7
Figure 9-Schematic of VU Meter and Pad 8
Figure 10-Loudspeaker Connections 9
Figure 11-Typical Conduit Layout 13
Figure 12-Simplified Block Diagram of Types 76-62 and 76-64 Consolettes 14
Figure 13-Announce Booth Relay Connections 17
Figure 14-Simplified Schematic of Control Circuits 18
Figure 15-Simplified Block Diagram of Types 76-62 and 76-64 Consolettes 22
Figure 16-Schematic Diagram (W-131973) 23
Figure 17-MI-11301-B Power Supply 25
Figure 18-Mounting Dimensions (MI -11301-B Power Supply) 26
Figure 19-Interior View of Power Supply 27
Figure 20- Wiring Diagram (MI-1 1301-BPower Supply) 28
Figure 21-Schematic Diagram (MI-1 1301-BPower Supply) 29
Figure 22-Rear View of Power Supply Chassis 30
Figure 23-Relay Mounting Plate Wiring 33
Figure 24-Line Transformer Wiring 34
Figure 25-Preamplifier Mounting Plate Wiring 35
Figure 26-Program Amplifier Mounting Plate Wiring 36
Figure 27-Monitor Amplifier Mounting Plate Wiring 37
Figure 28-Front Panel Wiring (W-131969) 39
Figure 29-Overall Wiring Diagram (W-131681) 41

iii
TECHNICAL DATA
Power Required
One MI -11301-B Power Supply or a -c, d -c supply
as follows:
a. D -C Plate Supply
Term. Volts Milliamperes
Radiotrons*
11 RCA -1620 or 11 RCA-6J7t
2 RCA -1621 or 2 RCA-6F6t
2 RCA -1622 or 2 RCA-6L6t
tMay be used when maximum uniformity of
characteristics, and minimum of microphonics,
116 375 62.0 hum, and distortion are not required.
115114 210278 1.25.1 Inputs
104 285 42.0 a. Six 30- or 250 -ohm microphone inputs
105 220 4.6 (balanced )
Reg. 245 16.0 b. Six line inputs, 150, 300, and 600 ohms
106 (balanced)
Emerg. 200 13.0 c. Two 250 -ohm transcription inputs (unbalanced )
b. A -C Filament Supply
Term. Volts Milliamperes
d. One 250 -ohm talk -back microphone input
(balanced )
112 and 113 6.2 2.7 e. Five 20,000 -ohm monitor cue lines (balanced )
109 and 110 6.2 1.6 Outputs
107 and 108 6.2 0.3 a. One 500- to 600 -ohm line
101 and 102
c. D -C Relay Supply
6.2 2.4 b. Three 15 -ohm monitor lines
c. One high -impedance headphone output (2,000
Term. Volts Milliamperes to 5,000 ohms)
117 and 118 60 100 Line Output Noise Level
Gaina. Microphone Input to Line Output: 112+2 db
b. Transcription Input to Line Output: 81 +1 1/2 db
c. Line Input to Line Output: 54+1 1/2 db
d. Microphone Input to Monitor Output:
110+2 db
e. Line Input to Monitor Output: 54+2 db
f. Transcription Input to Monitor Output:
80+2 db
g. Cue Input to Monitor Output: 34+2 db
h. Talk -back Input to Monitor Output: 95 +2 db
i. Line Output to Monitor Output: 33 ±2 db
j. Microphone Input to Emergency Line Output:
91+2 db
k. Remote Line through Override: 27 +21/2 db
1. External Record: 90+2 db
m. Remote Talk -back: 77+2 db
Line Output Level
Normal: +18 dbm** with 0.5% rms harmonic
distortion from 50 to 7,500 cycles
Maximum: +26 dbm** with 1% rms harmonic
distortion from 50 to 7,500 cycles
Microphone Input at -50 dbm, to Line Output
at 18 dbm** output (68 db system gain): -68 db
Microphone Input to Monitor Output at 4 watts
(+36 dbm**) output (86 db system gain ): -68 db
Distortion
a. Microphone Input to Line Output: 0.5% rms
harmonic distortion from 50 to 7,500 cycles,
with normal output of +18 dbm**
b. Microphone Input to Monitor Output: 11/2%
rms harmonic distortion from 50 to 7,500
cycles at 4 watts output
Frequency Response
a. Microphone Input to Line Output: +2.0 db
from 30 to 15,000 cycles
b. Microphone Input to Monitor Output: +2 db
from 30 to 15,000 cycles (audition channel)
Monitor Power Output
a. 4.0 watts ( +36 dbm**) with 11/2% rms
harmonic distortion from 50 to 7,500 cycles
b. 8.0 watts ( +39 dbm**) with 3% rms harmonic
distortion from 50 to 7,500 cycles
Physical Specifications
Width 39 inches
*TRADEMARK RADIOTRON- REG. U. 5. PAT. OFF. BY RADIO CORPORATION OF AMERICA
**dbm = decibel level referred to one milliwatt sine wave power.
Depth
Height
Weight
17 inches
10 1/2 inches
135 pounds

1
TYPES 76-B2 AND 76-B4 RCA CONSOLETTES
PART I
Installation
DESCRIPTION
The Type 76-B2 (MI -11613-B ) and Type 76-B4
(MI -11613-C) Consolettes have been designed for
use in Broadcast Audio installations to provide a
complete and flexible control system in one con-
veniently arranged unit. All the controls necessary
for switching and mixing the audio outputs of
microphones, transcription turntables and remote
lines, as well as for auditioning and monitoring,
are contained in a single cabinet. The Consolette
may be used as a complete control system for a
small station, or to control a single studio in larger
installations.
The Consolette consists of a metal cabinet con-
taining four pre -amplifiers, a program amplifier, an
eight -watt monitoring amplifier, two line trans-
formers and three loudspeaker relays. A VU meter
P -2211-I
Figure 1-Type 76-82 Consolette with Door Open IB-24454

2
attenuator controls, switches, and other controls
are mounted on a slanting front panel. An arrange-
ment of switches makes it possible to use the VU
meter to check the condition of the tubes in the
program channel.
The 76-B2 and 76-B4 Consolettes are similar in
performance and operation and the instructions for
installation and operation apply to both types
unless otherwise specified.
The top of the Consolette may be opened to
inspect and service the Radiotrons and relays or
the entire upper section, which is hinged at the
back, may be lifted to expose the terminal boards
and the bottoms of the mounting plates. As may be
seen in figure 2, three terminal boards are provided
for external connections. These are mounted on
the bottom section of the chassis and are accessible
when the upper section is lifted. The terminal
boards are arranged so that the low-level audio
terminals are separated from the high-level audio
terminals and the power leads.
Five rubber -cushioned mounting plates are lo-
cated on the hinged upper chassis as follows
(left to right):
a. Relay Mounting Plate, on which are mounted
three relays and their associated equipment. Two
terminal boards, on which connections are made to
change over from two- (or three-) studio operation
to single -studio operation are mounted under
this plate.
b. Monitor Amplifier Mounting Plate, on
which are mounted the components of the monitor
amplifier and the monitor amplifier booster stage.
c. Line Transformer Mounting Plate, on which
are mounted the two line transformers and asso-
ciated resistors.
d. Preamplifier Mounting Plate, on which are
mounted the four preamplifiers.
e. Program Amplifier Mounting Plate, on
which are mounted the components of the program
amplifier and the program amplifier booster stage.
ASSOCIATED EQUIPMENT
The additional apparatus required for operating
this equipment will be determined partly by the
particular installation, depending on the number of
studios and their arrangement. The installation
described in this book is designed to fulfill, as
completely as possible, the average requirements of
the type of broadcasting station for which the
Consolette is designed. These instructions will also
serve as a guide to the customer whose installation
is not exactly as described in these pages.
The associated equipment described below, or
its equivalent, will be required for a complete
installation.
Microphones
The Consolette is normally used with two micro-
phones in each of two studios, a fifth microphone
(for announcing) in the control room, and if
desired, a sixth for an announce or transcription
booth. Terminals 9 and 10 and 47 and 48 may be
connected in parallel if the same microphone is
used for control room announcing and talk -back.
The RCA 44-BX, 74-B, MI -6203-B or 77-D ribbon-
type microphones are recommended for program
pickup, the RCA Type 88-A Pressure Microphone
for control room announcing, and the RCA MI -
6226 Aerodynamic Microphone and MI -6227
Table Stand for the talk -back circuit.
Microphone Stands
The quality and type of stands required will
depend on the number and type of microphones
used. The most suitable program -type floor stand
for use with all the above mentioned microphones
is the RCA Type 90-A. Lower priced stands such
as the KS-lA and MI -4068-D are also available.
The Type 91-A Announce Type Desk Stand
(MI -4058-C) should be used with the 44-BX
microphone only, and the 91-B Desk Stand (MI -
4092 -C ) with the other microphones.
Transcription Turntables
The RCA 70-C2 Transcription Turntables are
recommended for the transcription booth or con-
trol room installations. They may be used with the
Type 72-D or 72 -DX Recording Attachment.
Recorders
If the highest quality recording equipment is
desired, the 73-A or 73-B Deluxe Recorder is
recommended. Suggested recording setups and
connection information are shown in figure 4.
Recording Amplifiers
The Type BA -4B or 82-C1 Recording Amplifiers
are recommended for driving either the 70-C2
Transcription Turntables, when used with the
recording attachment, or the 73-A and 73-B re-
corders. (See figure 4).
Loudspeakers
The RCA Type LC -1A loudspeakers should be
used in the control room, lobby, studios, and

3
Figure 2-Type 76-82 Consolette with Chassis Raised

4
listening rooms where the greatest fidelity is re-
quired. If high-fidelity reproduction is not required
for the studios and announce booth, other types
may be used instead of the Type LC -1A in these
locations.
Signal Lights and Relays
The MI -11706 series of studio signal lights are
recommended for use in the studios, announce
booth and control room. These lights are available
with the inscriptions listed below and may be
ordered to suit the purpose for which the studios
will be used.
STUDIO WARNING LIGHTS
MI -Number Inscription
MI -11706.1
MI -11706-2
MI -11706-3
MI -11706-4
MI -11706-5
ON AIR
REHEARSAL
AUDITION
STAND BY
SILENCE
The relays and additional equipment required for in
stalling this equipment are listed under Addition of Signal
Lights.
Figure 3-6 db Pad for Telephone Lines
Power Supply
The MI -11301-B Power Supply will furnish all
the voltages necessary to operate the 76-B2 or
76-B4 Consolette and its associated relay control
system. The required voltages are listed under
Technical Data and instructions for installation and
operation of the power supply are given in part III
of this book.
Conduit Terminating Box
A conduit terminating box of the type shown in
figure 7 is required to install the 76-B2 or 76-B4
Consolette. In many cases this box is made by the
electrician or manufactured on special order. In
such cases the mounting flanges may be turned
outward instead of inside as shown in figure 7.
6DB Pad for Telephone Line
When used with some types of lines, a 600- to
600 -ohm pad (MI -4171-29) should be connected
between the output terminals of the Consolette and
the telephone line jacks to permit the Consolette to
operate into a constant impedance at all times.
The resistors for a similar pad may be ordered
as follows:
a. Resistor, 100 ohms RCA stock number
34765 (4 required )
b. Resistor, 400 ohms RCA stock number
30498 (2 required )
The resistors should be mounted in a rack or wall
box as described below and connected between the
600 -ohm Line Out terminals of the Consolette and
the telephone line jacks as shown in figure 3.
BR -84 Rack or MI -11500 Wall Box
The 6 db telephone pad described above as well
as the line jacks and line equalizers may be mounted
in an MI -11500 Wall Box or on a type BR -84 Rack
if more space is required. The MI -11500 Wall Box
will accommodate up to four MI -4645-A (Type
33-A) or six MI -4646-A (Type 33-B) Jack Panels
and one MI -4162 (Type 56-E) Line Equalizer.
Radiotrons
The types and numbers of Radiotrons required
are listed under Technical Data.
Wall and Floor Outlets
Wall and floor outlets for microphones, signal
lamps, loudspeakers, and turntables are shown in
the typical conduit layout in figure 11. Recom-
mended outlets and boxes are listed in the drawing.

5
CONSOLETTE 120^
(41 EXTERNAL
RECORDING
AMPLIFIER42
TYPE BA -IA
z OR BA -2A 1;
-BOOSTER o
AMPLIFIER
120"
REMOVE GROUND ON PRIMARY
OF INPUT TRANSFORMER
OF TYPE BA -2A AMPLIFIER.
TYPE BA -2A AMPLIFIER
CONNECTED FOR 250" INPUT
AND 600 ^ OUTPUT.
CONSOLETTE 120 -11-
41 0--4AA/1--0 0
EXTERNAL
RECORDING
AMPLIFIER
"PC
L
1
TYPE BA -4A AMPLIFIER
VOLUME CONTROL
"Bn
TYPE BA -4A
AMPLIFIER
42 0--ANV--o 0
120 "
REMOVE GROUND ON CENTER TAP
OF INPUT TRANSFORMER
OF BA -4A AMPLIFIER.
TYPE BA -4A AMPLIFIER
CONNECTED FOR 250 " INPUT
AND 15" OUTPUT.
TYPE BA -4A
-(30ND.AMPLIFIER
TYPE BA -4A AMPLIF ER
CONNECTED FOR 250." INPUT
AND 15" OUTPUT.
RECORDER
RECORDER
120^ RESISTOR - RCA STOCK NO. 30199
560 a RESISTOR - RCA STOCK NO. 5164 P -1743I3
Figure 4-Suggested Recording Setups
PN-3 V.U. METER PK-I
orbO "616-4,7, -6 6
PK-4
OVERRIDMaRECCRO
N-9
noes0MONITOR MOTE
PRO
TURK CHEOt VI. CONTROL 677
0 067600
TT ?12345 6
ia
0 0 On9u9pu0 00
T
*1 It2 Its3 K-4 K-5 Ki K-13 ----PK-2
LINE OUT
A)33 AL33P Ar-CmP AcCMP A606 ASP ENG cCo REG
000tEmra MASTER
J -I P-2 K -I0
MIXERS
K-7 P -I
P-170505-3
Figure 5-Front Panel Layout