CBS laboratories 4100 Manual

OPERATING AND MAINTENANCE INSTRUCTIONS
o
OCTOBER 1972
Models, 4100,4110
FM Volumax
PROFESSIONAL PRODUCTS
CBS LABORATORIES
A Division of Columbia Broa casting System, Inc.
Stamfor , Connecticut 06905

Section
TABLE OF CONTENTS
Title
INSTALLATION
Unpacking
Mec anical Installation and Operation Considerations
Power Source
Electrical Connections
THEORY OF OPERATION
General
Input Section (Board A2 or A5)
AGC Amplifier (Board A3)
Hig Frequency Processor (Board Al or A4)
Output Section (Board A2 or A5)
Power Supply (Board A3)
OPERATIONAL SET-UP
General
Set-Up of Stereop onic FM Volumax Unit
Set-Up of Monop onic FM Volumax Unit
Proof-of-Performance Measurements
MAINTENANCE
General
Alignment Procedure
Troubles ooting Input Section (Board A2 or A5)
Troubles ooting Hig Frequency Control Section
(Board Al or A4)
Troubles ooting Output Section (Board A2 or A5)
Troubles ooting AGC Section (Board A3)
Troubles ooting Gain Meter Circuit
INTRODUCTION
General
Functional Description
P ysical Description
Warranty
Service and Repair
Specifications
5
6
7
2
2
2
5
5
5
o
1
2
3
4
,
_
_
_
一
V
5
5
5
5
1
2
3
4
n
2
-
1
2
3
4
5
6
_
_
_
_
_
_
I
1
1
1
1
1
1
1
2
3
4
1
2
3
4
5
6
H
3-
3-
3-
3-
W
4-
4-
4-
4-
4-
4
-
•
1
1
1
2
2
5
5
6
1
1
1
4
7
1
1
1
4
4
1
1
3
5
6
8
9
1
1
2
6
6
1
1
1
1
1
1
1
3
3
3
3
3
2
2
2
2
2
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
7
9

TABLE OF CONTENTS (cont)
o
Page
Title
Section
VI
7-1/7-2
DRAWINGS
vn
LIST OF ILLUSTRATIONS
Title Fig. No.
o
1-3 1-4
1-4
1-4
2-4
2-8
3-1 FM Volumax Controls
3-0
5-1
5-0
o
ii
1-1
1-2
FM Volumax Block Diagram
FM Volumax Amplitude Response
4-0
4-4
4-1
4-2
2-1
2-1
2-2
2-3
Locations of Circuit Boards and C assis Parts in
FM Volumax Unit
FM Volumax Automatic Peak Controller
Area of Potential FM Overmodulation (75-四
Pre-Emp asis Curve)
Diagram and Oscilloscope P otos S owing Audio
Peak Levels of Cymbal Clas wit and wit 
out Pre- Emp asis
Simplified Block Diagram, FM Volumax Model 4100
1-1
1-3
6-1
6-1
6-1
6-1
6-2
6-3
6-4
6-7
6-10
6-13
PARTS LISTS
General
Resistors
Diodes and Transistors
Manufacturers f Name Abbreviations
Main Assembly (Model 4110 or 4100)
Hig Frequency Board Al and A4
Input-Output Board A2 and A5
Power Supply and AGC Board A3
Front Panel Assembly A6 (Model 4110 or 4100)
2-2
2-3
2-5
2-6
Outline Drawing (S eet 1 of 2 S eets)
Outline Drawing (S eet 2 of 2 S eets)
Typical FM Volumax Installation Block Diagram
Typical Attenuator for FM Volumax Input Line
(Sc ematic Diagram)
Transformer T1 or T3 Re-Strapping Connections
for 150-O m Operation
1
2
3
4
5
6
7
8
9

LIST OF ILLUSTRATIONS (cont)
Title
Fig. No. Page
7-7/7-8
7-3
7-9/7-10
7-4
LIST OF TABLES
Title Page
Table No.
o
o
iii
5-1
5-2
7-1
7-2
Power Supply Voltages
Ac Signal Voltages
5-9
5-9
7-3/7-4
7-5/7-6
FM Volumax, Internal Interconnections
Hig Frequency Processor Board Al or A4,
Sc ematic and Parts Location Diagrams
Input-Output Board A2 or A 5, Sc ematic and Parts
Location Diagrams
Power Supply-AGC Board A3, Sc ematic and Parts
Location Diagrams

SECTION I
INTRODUCTION
1-1. GENERAL
T is manual provides instructions for t e CBS Laboratories Model 4100
(Monaural) and Model 4110 (Stereo) FM Volumax* automatic audio peak con 
trollers.
T ese instruments ave been designed for use in FM and TV broadcast 
ing applications in w ic t e use of pre-emp asis is mandatory. Eit er
instrument will enable t e full modulation capability of t e transmitter to be
utilized wit no risk of overmodulation. It replaces any limiter or clipper t at
may now be in use. W en used wit SCA** systems, it prevents crosstalk
caused by overmodulation from entering into adjacent c annels . It s ould be
operated wit well-controlled audio input levels suc as provided by t e CBS
Laboratories Audimax* automatic level control.
Figure 1-1. FM Volumax Automatic Peak Controller
1-1
FM VOLUMAX
*
**
CBS Laboratories Trademark
Subcarrier Aut orization

INTRODUCTION

1-2. FUNCTIONAL DESCRIPTION
T e Models 4100 and 4110 are late designs based on t e foundation
establis ed in t e earlier Model 410 FM Volumax unit. T ey extend t e
original tec nology to yield a cleaner, brig ter sound w ile still retaining
absolute protection against overmodulation.
A very familiar problem in FM and TV broadcasting is caused by t e
mandatory 75-p.s pre-emp asis curve (fig. 1-2). T is is a long establis ed
requirement of t e FCC for t e improvement of t e overall signal-to-noise ratio.
At t e time t e FM and TV broadcasting standards were adopted, t e long-term
average spectral distribution of music signals s owed a steady decline wit
frequency above 1, 000 Hz. T is meant t at ig -frequency pre-emp asis wit
subsequent de-emp asis at t e receiver could be employed to improve t e over 
all signal-to-noise ratio. However, in recent years, improvements and ot er
c anges in recording tec niques in conjunction wit social c anges in musical
style ave led to increasing problems wit t e overmodulation caused by ig -
amplitude ig -frequency program signals.
T e FM Volumax unit solves t is problem uniquely by quadruple - action
control. Low-, middle-, and ig -frequency portions of t e program wave are
independently processed and overall, instantaneous , final limiting is used to
assure t at no overmodulation will occur. See also figures 1-3 and 1-4.
1-3.
PHYSICAL DESCRIPTION
T e Models 4100 and 4110 FM Volumax units are oused in t e same new
o
slimline packages as t e CBS Laboratories Audimax and a-m Volumax units.
1-2

INTRODUCTION
MODULATION
800%
18
16
14
400%
8
o
200%
6
4
2
0
100%
2
5
100
2
1000 5
10 20000 5
20
1-3
Figure 1-2. Area of Potential FM Over 
modulation (75-ps Pre-Emp asis
Curve)
io
db

INTRODUCTION
>
9 B
pre-emphasis
1-4
Figure 1-3. Diagram and Oscilloscope P otos
S owing Audio Peak Levels of Cymbal
Clas wit and wit out Pre-Emp asis
Figure 1-4. Simplified Block Diagram, FM Volumax
Model 4100
O B

INTRODUCTION
o
T is package requires only 1-3/4 inc es of eig t in a standard 19-inc rack
and 18-1/2 inc es of dept be ind t e front panel. T e reliable solid-state
circuitry is functionally packaged on t ree circuit boards in t e monaural
FM Volumax model and on five circuit boards in t e stereo model. Bot models
are equipped wit appropriate test points to speed t e process of maintenance
tests or troubles ooting procedures.
T e entire unit slides forward on rack slides for easy servicing wit out
disconnections from t e transmitting system. Front panel controls are
conveniently arranged and, in t e stereo unit, are grouped according to c annel- -
left c annel controls on t e left of t e unit and rig t c annel controls on t e
rig t of t e unit. A front panel meter indicates t e relative degree of gain re 
duction.
o
T e unit can be operated from eit er a 115- volt or 230-volt single-p ase
50- or 60-Hz power source. On delivery, t e unit is wired for 115-volt opera 
tion. Wiring c anges for 230-volt operation are explained in paragrap 2-3.
1-4. WARRANTY
A standard warranty card as been included wit your FM Volumax unit.
To validate your warranty, complete and return t e postcard section to CBS
Laboratories as soon as possible.
1-5. SERVICE AND REPAIR
If t ere is difficulty in operating or maintaining your FM Volumax unit,
call on your local aut orized distributor from w om you originally purc ased t e
o
unit. If you do not know t e name and address of your local distributor, call
1-5

INTRODUCTION
CBS Laboratories, Professional Products Department, Stamford, Conn. ,
06905, telep one [phone].
1-6. SPE CIFICATIONS
Input impedance
Output impedance
600 or 150 o ms, balanced or unbalanced
-22 dBm to +8 dBm
Input level
Maximum peak output level +28 dBm
Frequency response
Harominc distortion.
Attack time
Recovery time
Signal-to-noise ratio
Greater t an 70 dB.
Wit in 1/2 dB
Amplitude
P ase
Wit in 1. 5 degrees
+55°C. (+130°F)
1-6
200 ms (low frequencies )
5 ms (middle frequencies)
1 阳 or less ( ig frequencies )
Less t an 1%, below t res old of limiting,
50 - 15, 000 Hz.
Maximum operating
temperature
Tracking accuracy
(stereo, model):
Between 1 |is and 2 ms, depending on
program waveform.
600 o ms, balanced or unbalanced; 10
kilo ms or 150 o ms available on
request.
±1 dB, 50 - 15, 000 Hz below limiting
t res old. Variable as a function of level
above limiting t res old, reac ing t e
75-|is de-emp asis c aracteristic ±1 dB
at maximum level.