ELCOM INSTA-PEAK II User manual

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I •
TECHNICAL MANlW..
INSTA-PEAK II
DUAL SPECTRUM AUDIO PROCESSOR
M)DEL AP-50 FM
FOR FM RADIO AND TEI..EVISION
ELOJM SPECIALTY PRODUCTS, INC.
2810 REDDING _f.VENUE S'IE. E
SACRAMENTO, CALIFORNIA 95820
[phone]

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TABLE
OF
CONTENTS
SECTION
TITLE
1 INTRODUCTION
1.
1
GENERAL
"}
'
1.2
~ - FUNCTIONAL DESCRIPTION
1.
3 .,
1
·
PHY? I
CAL
DES
CR
I PT I
ON
1.4
.,i
,.
SERVICE
AND
REPAIR
PAGE
1-1
1-1
1-1
1-2
1-2
·.
'
..
·
1.
5 ·.:
WARRANTY
1-
~
1.6
SPECIFICATIONS
1--3
I I INSTALLATION
2-1
2.1
MECHANICAL INSTALLATION
2-1
2,2
ELECTRICAL CONSIDERATION
FOR
-
BROADCAST
USE
2-1
2.3
USE
OF
PRE-EMPHASIS
AND
DE-EMPHASIS
2-1
2,4
STEREO INTERCONNECTION
2-2
2.5
ELECTRICAL CONNECTIONS
2-2
I I I OPERATIONAL
SET-Uf
3-1
3,1
GENERAL
3-1
3.2
:
CONTROL
SETTINGS
3-1
3.
3
:,
· PROOF-OF-PERFORMANCE
MEASUREMENTS
3-2
IV
f,
THEORY
OF
OPERATION
4-1
4.
1
i~-
GENERAL
4-1
4.2
INPUT LEVEL CIRCUITRY
5-1
V
MAINTENANCE
AND
REPAIR
5-1
5.
1
GENERAL
/

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TABLE
OF
CONTENTS
(CONT.)
SECTION
TITLE
5.2
ACCESS
TO
INTERNAL
COMPONENTS
5.3
TROUBLE
SHOOTING
METHODS
5.4
CHECK
OF
BALANCE
CONTROL
SETTING
5.5
ADJUSTMENT
OF
GAIN
REDUCTION
METER
ZERO
PAGE
5-1
5-1
5-1
5-2

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LIST
OF
ILLUSTRATIONS
FIGURE
NO,
TITLE
2.1
AUDIO
ATTENUATOR
NETWORKS
4,1
FUNCTIONAL
BLOCK
DIAGRAM
,.
5.1
•i'
\·
I\
SCHEMATIC
DIAGRAM-MAIN
SECTION
I
t ,
'«t
i'
'
5.2
'I'{,
, /, .
.,
·'
)
r.'
SCHEMATIC
DIAGRAM-POWER
SUPPLY
5.3
1}
J
f'·
',
'if/,
TABLE
OF
TEST
POINT
VOLTAGES
5,4
•,•,,1~1
..-,
I
~OC~TION
OF
COMPONENTS
AND
TEST
..
,.::.
'·
.
.
..
POINTS
/
PAGE
2-0
4-0
s-o
5-3
,
5-4
5-5

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SECTION
I
INTRODUCTION
1,1
GENERAL
THIS
MANUAL
PROVIDES
INSTALLATION,
OPERATING
AND
MAINTENANCE
INSTRUCTIONS
FOR
THE
ELCOM
ENGINEERING
COMPANY,
MODEL
AP-50
FM
INSTA-PEAK
II
AUDIO
PROCESSOR.
'
,. .
THE
MODEL
AP-50
FM
IS
DESIGNED
FOR
USE
WITH
FM
BROADCAST
AND
TV
TRANSMITTERS
WHERE
PRECISE
CONTROL
OF
DYNAMIC
RANGE
AND
AUDIO
TRANSIENTS
IS
ESSENTIAL,
IT
ALLOWS
THE
FULL
USE
OF
TRANSMITTER
MODULATION
C~PABILITY
'.
WITHOUT
THE
RISK
OF
OVER-MODULATION,
CONT-
INUOUS
LEVEL
COMPRESSION
OF
20
DB
IS
ACHIEVABLE
WITHOUT
AUDIBLE
DISTORTION
$UCH
AS
LEV~L
PUMPING,
THIS
IS
MADE
POSSIBLE
BY
USE
OF
PASSIVE
OPTICAL
ATTENUATORS,
SPLIT
SP~CTRUM
AUDIO
DISTRIBUTION,
INTERNAL
PRE-EMPHASIS
AND
DE-EMPHASIS,
AND
SPECIAL
ANTI-RING
CIRCUITRY
WHICH
PREVENTS
OVER-MODULATION
CAUSED
BY
FREQUENCY
SELECTIVE
NETWORKS
WITHIN
MOST
STEREO
GENERATORS
ANO
EXCITERS.
1,2
FUNCTIONAL
DESCRIPTION
THE
UNIQUE
LEVEL
CONTROL
METHOD
TOGETHER
WI
TH
THE
"SPLIT-
SPECTRUM"
TECHNIQUE
PROVIDES
AUTOMATIC
LEVEL
AND
PEAK
CONTROL
WHICH
IS
IN-AUDIBLE
TO
THE
LISTNER
EVEN
WITH
HIGH
COMPRESSION
RATIO,
TESTS
INDICATE
THAT
IN
ORDER
TO
PREVENT
THE
AUDIBLE
PUMPING
EFFECTS
Of
ORDINARY
LEVEL
CONTROL
SYSTEMS
THE
AUDIO
SPECTRUM
CAN
BE
SP~IT
INTO
TWO
SEGMENTS,
APPROXIMATELY
10
TO
700
HZ
AND
100
TO
15
1
000
HZ,
EACH
OPERATING
WITH
SEPERATE
LEVEL
CONTROL,
DIVIDING
THE
SPEC~RUM
INTO
MORE
SEGMENTS
INCREASES
THE
EQUIPMENT
COMPLEXITY
/
AND
ADDS
NOTHING
TO
THE
PERFORMANCE,
THIS
SPLITTING
TECHNIQUE
HAS
BEEN
KNOWN
FOR
20
OR
30
YEARS,
BUT
HAS
NOT
BEEN
WIDELY
USED
·
1-1

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UNTIL RECENTLY, THE SPLIT SPECTRUM TECHNIQUE IS COMBINED WITH
A LEVEL CONTROL SYSTEM UTILIZING PHOTO CONDUCTIVE CELLS AS
AUTOMATIC VARIABLE ATTENUATORS FOR SMOOTH DISTORTIONLESS OPERATION,
THE INITIAL RESPONSE DELAY OF THE Ar TENUATOR TO A SUDDEN AUDIO
INPUT MAY BE SEVERAL MILLISECONDS, SO TO PREVENT THE PASSAGE OF
SUCH A PEAK THROUGH THE SYSTEM A PAIR OF LIGHT EMITTING DIODES CLAMP
THE LEVEL FOR A FEW CYCLES UNTIL THE ATTENUATOR CELLS CAN RESPOND
AND TAKE CONTROL, MOST FM STEREO GENERATORS AND EXCITERS EXHIBIT
AUDIO ' 0VER-SHOOT AND RINGING WHEN SUBJECTED TO FAST RISE AND FALL
OF THE AUDIO WAVE FORM SUCH AS CAN BE CAUSED BY THE HARD LIMITING
NECESSARY FOR TIGHT CONTROL OF CEILING AMPLITUDE. THE ELCOM INSTA-
PEAK II USES A PROPRIETARY "ANTI-RING" . CIRCUIT TO PREVENT OVER-
SHOOT AND RINGING.
113 PHYSICAL DESCRIPTION
THE INSTA-PEAK II IS SELF-CONTAINED IN A WELL SHIELDED
MODULE DESIGNED TO MOUNT IN THE STANDARD ELCOM RACK MOUNTING
FRAME. THE INSTA-PEAK II MODULES CAN BE INSTALLED IN THE FRAME
FOR STEREO OPERATION.
WHEN A SINGLE INSTA-PEAK II IS USED THE ADJACENT MODULE
SPACE IS COVERED WITH A BLANK PANEL THAT IS SUPPLI E D, A DEPTH OF
12 INCHES BEHIND THE FRONT PANEL IS USED,
A FRONT PANEL METER AND SELECTOR SWITCH INDICATES INPUT
LEVEL, GAIN ~~DUCTION
1
IN DB, AND OUTPUT LEVEL.
1.4 SERVICE AND REPAIRS
. .
IF YOU HAVE DIFFICULTY IN OPERATING OR MAINTAINING YOUR
INSTA-PEAK II CALL YOUR LOCAL AUTHORIZED DJSTR{BUTOR FROM WHOM
YOU ORIGINALLY PURCHASED THE UNIT, OR CALL ELCOM ENGINEERING
COMPANY IN SANTA ANA, CALIFORNIA,
1-2

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1,5
WARRANTY
A
STANDARD
ELCOM
WARRANTY
CARD
HAS
BEEN
INCLUDED
WITH
YOUR
INSTA-PEAK
II.
TO
VALIDATE
YOUR
WARRANTY,
COMPLETE
AND
RETURN
THE
POSTCARD
SECTION
TO
ELCOM
AS
SOON
AS
POSSIBLE.
1,6
SPECIFICATIONS
INPUT
IMPEDANCE:
600
OHMS,
BALANCED
OR
UNBALANCED.
OUT~UJ
LOAD
·
IMPEDANCE:
600
OHMS
NOMINAL
LOAD,
TRANSFORMER
ISOLATED.
OUTPUT
SOURCE
IMPEDANCE:125
OHMS.
OUTPUT
LEVEL
(MAX.):
INPUT
LEVEL:
FREQUENCY
RESPONSE:
HARMONIC
DISTORTION:
ATTACK
TIME:
RECOVERY
TIME:
SIGNAL
TO
NOISE
RATIO:
POWER
~
~EQU~R~M&Nt$:
DIMENSIONS
(WITH
MO~N
lt~
~
FRAME):
20
DBM.
-50
DBM
TO
+10
DBM.
±1
DB
50-15,000
HZ
WITH
OR
WITHOUT
GAIN
REOUCTI
ON.
-
LESS
THAN
1\
WITH
OR
WITHOUT
GAIN
REDUCTION
AND
+20
DBM
OUTPUT.
INSTANTANEOUS.
0.5
TO
2
SECONDS
DEPENDING
ON
PREVIOUS
GAIN
REDUCTION.
GREATER
THAN
65
DB.
6
WATTS
100~130
VOLTS
50/60
HZ.
3
1/2
I
NCHES
HIGH,
19
INCHES
WIDE
AND
12
INCHES
DEEP.
/
1-3

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600 OHM
INPUT ··
... \ tr;;; '
'.:.• .. "·
r)R I fl,,
10 (
11)
15
'
20
24
30
.
•
Rl
~ l30
430
510
510
560
2-0
600 OHM
OUTPUT
Q?
360
220
120
75
39
AUDIO ATTENUATOR NETWORK
FIGURE 2-'l

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SECT
I
ON
II
INSTALLATION
211
MECHANICAL
INSTALLATION
THE
INSTA-PEAK
II
MODULES
ARE
SUPPLIED
IN
A 3
1/2
INCH
HIGH
,,~K
MOUNTING
FRAME.
THE
FRAME
WILL
HOLD
TWO
MODULES
OR
ONE
Mi9,ULE
~ITH
A
BLANK
PANEL.
THE
MODULES
ARE
EASILY
REMOVED
BY
M~~~S
OF
TWO
THUMB
SCREWS.
THE
MODULES
REQUIRE
12
INCHES
OF
DEPT~
_
BEHINO
THE
FRAME.
A
LOCATION
SHOULD
BE
SELECTED
WHICH
WILL
PROVIDE
EASY
ACCESS
·~
·
ANO
~L~~
~-
..
G?_9D
..~I·
E~
--
OF-
..
THE
.
FRON
_!
PANEL
METER
•.
THE
IN
STA-PEAK
.
II
SHOULD
NOT
BE
LOCAJED
D~RECTLY
ABOVE
HEAT
PRODUCING
EQUIPMENT.
2.2
ELECTRICAL
CONSIDERATIONS
FOR
BROADCAST
USE
THE
lNSTA-PEAK
11
HAS
SUFFICIENT
GAIN
TO
OPERATE
DIRECTLY
FROM
AN
EQUALIZED
TELEPHONE
LINE
AND
A
+20
DBM
OUTPUT
CAPABILITY
WHICH
IS
MORE
THAN
AMPLE
TO
ALLOW
DIRECT
CONNECTION
TO
THE
TRANS-
MITTER.
MOST
TRANSMITTERS
REQUIRE
AN
INPUT
LEVEL
OF
+10
DBM
FOR
100%
MODULATION.
JF
THE
INSTA-PEAK
I I
IS
TO
BE
USED
AT
THE
STUDIO
OR
IF
IT
IS
'I
I
~
TO
s;
1
~PERATED
FROM
A
STL
llECEIVER,
SUFFICIENT
FIXED
AUDIO
ATTE~~ATIO~
SUCH
AS
A
II
T"
PAD
SHOULD
BE
INSTALLED
AHEAD
OF
THE
fNPUT
TERMINALS.
A
10
OB
ATTENUATOR
AT
THE
OUTPUT
TERMINALS
IS
.~:.
'
RECOMMENDED
WHEN
FEEDING
A
TELEPHONE
LlNE
SO
THAT
THE
NORMAL
AMPLIFIER
$UTPUT
CAN
BE
SET
FOR
+10
DBM.
ATTENUATOR
CIRCUITS
AND
COMPONENT
VALUES
ARE
GIVEN
IN
FIGURE
2.1.
/
2.3
USE
OF
PRE-EMPHASIS
AND
DE-EMPHASIS
THE
INSTA-PEAK
JI
CONTAINS
PRE-EMPHASIS
AND
A
DE-EMPHASIS
·
CIRCUITS
IN
THE
MAIN
AMPLIFIER
CHAIN
FOR
THE
PURPOSE
OF
HIGH
FREQUENCY
WAVE
FORM
INTEGRATION
AND
INTERNAL
NOISE
REDUCTION.
2-1

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THE
LEVEL
CONTROLLING
AMPLIFIER
USES
SUFFICIENT
PRE-EMPHASIS
TO
COMPENSATE
FOR
THE
75
OR
25
MICROSECOND
RESPONSE
RISE
IN
THE
TRANSMITTER.
2,4
STEREO
INTERCONNECTION
WHEN
A
PAIR
OF
INSTA-PEAK
11
PROCESSORS
ARE
USED
FOR
STERE~
.
,ROAOCASTING,
THE
LEFT
ANO
RIGHT
CHANNEL
GAIN
REDUCTION
CIRCUIJ$
CAN
BE
INTER-CONNECTED
BY
MEANS
OF
THE
JUMPER
CABLE
,,\
'\·
1
SUPPLl~Q,
THIS
CAUSES
BOTH
CHANNELS
TO
HAVE
EQUAL
GAIN
REDUCTION
•
·,'
!
•,I
EVEN
T~OUGH
ONLY
ONE
CHANNEL
ACTUALLY
REQUIRES
COMPRESSION
OR
GAIN
1 I
,'•,
REDUCTION.
THE
SAME
TECHNIQUES
CAN
BE
USED
FOR
QUADROPHONIC
BROADCASTING.
HOWEVER,
A
SPECIAL
INTER-CONNECTION
CABLE
IS
REQUIRED.
215
ELECTRICAL
CONNECTIONS
THE
flVE
TERMINAL
BARRIER
STRIP
LOCATED
ON
THE
REAR
OF
THE
.-
.
INSTA-PEAK
II
IS
USED
FOR
INPUT
AND
OUTPUT
CONNECTIONS
AS
WELL
AS
\ .
SHIELD
GROUND.
POLARITY
OF
THE
INPUT
AND
OUTPUT
LINES
MUST
BE
OBSERVED
WHEN
CONNECTING
FOR
STEREO
OPERATION.
NOMINAL
INPUT
AND
OUTPUT
IMPEDANCES
ARE
600
OHMS
WITH
TRANSFORMER
JSOLATION.
THE
OUTPUT
SOURCE
IMPEDANCE
IS
125
OHMS
•
.
~
THE
STEREO
INTER-CONNECTION
CABLE
PLUGS
INTO
THE
JACKS
\
·•
!1
/
2-2

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SECTION
III
OPERATIONAL
SET-UP
},l
GENERAL
ALL
OF
THE
NECESSARY
OPERATIONAL
CONTROLS
ARE
LOCATED
ON
THE
FRONT
PANEL
OF
THE
INSTA-PEAK
II.
ACCESS
TO
THE
CONTROL
SHAFTS
11
•,
:.
1,
IS
SU~H
THAT
THEY
CONNOT
BE
TURNED
WITHOUT
THE
USE
OF
A
SCREWDRIVER,
·J
•;:.
BUT
'Tttf
ROTATIONAL
POSITION
OF
EACH
CONTROL
IS
CLEARLY
VISIBLE.
,d
!:'
!.'
.(
I
KNO~S
FOR
USE
WITH
THESE
CONTROLS
ARE
AVAILABLE
ON
REQUEST.
',
~
, l
THE
V.U.
TYPE
METER
CAN
BE
SWITCHED
TO
READ
OUTPUT
LEVEL
OR
GAIN
R~pUCTION
(COMPRESSION)
IN
DB.
IN
THE
-
OUTPUT
POSITION
0
DB
-
ON
:
TH~
METER
IS
ADJUSTED
(R46)'
TO
CORRESPOND
TQ
+5
DBM
FOR
STEREO,
~NQ
·+10
DBM
FOR
'\
OTHER
APPL1CATIONS
SUCH
A.M.
OR
MONAURAL
fM.
FOUR
VARIABLE
CONTROLS
ARE
ACCESSABLE
ON
THE
FRONT
PANEL.
INPUT
LEVE~
CONTROL
SETS
THE
INPUT
TO
THE
HIGH
AND
LOW
FREQUENCY
CHANNEL
AMPLIFIERS.
THE
GAIN
REDUCTION
CONTROL
SETS
THE
AMOUNT
OF
COMPRESSION
OR
LIMITING
TO
BE
USED.
THE
SPECTRUM
BALANCE
ADJUSTS
.
( .
THE
_
OVl;~ALL
.j•
JREQUENCY
RESPONSE
BY
OBTAINING
EQUAL
OUTPUT
FROM
THE
' ~\
,.
,:t
,
...
;1
HIGH
AND
LOW
FREQUENCY
AMPLIFIERS,
OR
UNEQUAL
OUTPUT
FOR
HIGH
.
OR
':
f,
I·
t
I
LOW
.
F~eQUENCY
BOOST,
.
:-
l
1
:,•t
.
THE
'
OUTPUT
LEVEL
CONTROL
IS
USED
TO
SET
THE
INSTA-PEAK
II
I
:•
,,J
"¢
•:
I •
OUTPUT
TO
THE
DESIRED
LEVEL
AFTER
THE
INPUT
AND
GAIN
REDUCTION
CONTROLS
HAVE
BEEN
SET.
3,2
CONTROL
SETTINGS
,'
SET
UP
FOR
MAXIMUM
AVERAGE
LEVEL
AND
ABSOLUTE
PR
E
VENTION
OF
OUTPUT
OVERMSHOOT
OR
PEAKS
EXCEEDING
A
PRE~SET
LIMIT
IS
RELATIVELY
EASY
SINCE
CONTROL
INTERACTION
IS
I
MINIMIZEO
,
BY
THE
SYSTEM
3-1

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EMPLOYED
IN
THE
INSJA-PEAK
II.
AFTER
COMPLETING
THE
INSTALLATION
AS
DESCRIBED
IN
THE
PRECEEDING
SECTIONS,
APPLY
NORMAL.PROGRAM
MATERIAL
TO
THE
INPUT
OF
THE
INSTA-PEAK
II.
A
STEADY
STATE
TONE
CAN
BE
USED
IN
PLACE
OF
PROGRAM
MATERIAL,
BUT
THE
FINAL
GAIN
REDUCTION
SETTINGS
SHOULD
BE
MADE
WITH
THE
PROGRAM
APPLIED
•
....
.
THE
GAIN
REDUCTION
CONTROL
IS
INDEPENDENT
OF
ALL
OTHER
CONTROLS
SO
(T
.
CAN
~i
ADJUSTED
TO
PROVIDE
THE
DESIRED
¼MOUNT
OF
GAI~
REDUCTION
AS
OBSERVED
ON
THE
FRONT
PANEL
METER,
A
TYPICAL
INITIAL
~
SETTING
CAN
BE
FOR
5
DB
Of
GAIN
REDUCTION
ON
AVERAGE
PROGRAM
LEVELS.
PRELIMINARY
STEREO
SET-UP
SHOULD
BE
MADE
WITH
THE
STEREO
INTER-
CONNECTION
CABLE
REMO~ED.
THE
INPUT
LEVEL
CONTROL
IS
THEN
ADVANCED
UNTIL
THE
POSITIVE
AND
NEGATIVE
CEILING
LAMPS
JUST
BEGIN
TO
FLASH
ON
PROGRAM
PEAKS.
THE
OUTPUT
LEVEL
CONTROL
CAN
NOW
BE
TURNED
CLOCKWISE
UNTIL
THE
DESIRED
OUTPUT
LEVEL
IS
OBTAINED
AS
INDICATED
BY
SWITCHING
THE
METER
TO
THE
OUTPUT
POSITION
OR
BY
CHECKING
THE
TRANSMITTER
FOR
100%
MODULATION.
THE
BALANCE CONTROL
MUST
BE
SET
TO
THE
RED
DOT
ON
THE
PANEL
(FLAT
RESPONSE)
DURlNG
.
THE
ABOVE
SET-UP
PROCEDURES.
UPON
COMPLETION
OF
THE
SET-UP
THE
BALANCE
CONTROL
CAN
BE
TURNED
SLIGHTLY
CLOCKWISE
TO
IN~REASE
THE'
HIGH
FREQUENCY
RESPONSE,
AND
COUNTER-CLOCKWISE
TO
INCREASE
THE
LOW
FREQUENCY
RESPONSE.
IT
SHOULD
BE
NOTED
THAT
A
DRASTIC
DEVIATION
FRQM
THE
BALANCED
OR
FLAT
RESPONSE
SETTING
MAY
INTRODUCE
SOME
PUMPING
EFFECT
DURING
HEAVY
GAIN
REDUCTION,
/
3,3
PROOF-OF-PERFORMANCE
MEASUREMENTS
BROADCAST
PROOF-OF-PERFORMANCE
MEASUREMENTS
MUST
BE
MADE
.
WITHOUT
COMPRESSION,
SINCE
IT
WOULD
BE
IMPOSSIBLE
TO
OBTAIN
MEANINGFUL
3-2

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FREQUENCY
RESPONSE
·
MEASUREMENTS
WITH
AUTOMATIC
LEVEL
CONTROL,
THE
COMPRESSION
ACTION
CAN
BE
DISABLED
BY
TURNING
THE
GAIN
REDUCTION
CONTROL
FULLY
COUNTER-CLOCKWISE
AND
ADJUSTING
THE
INPUT
AND
OUTPUT
CONTROLS
FOR
NORMAL
MODULATION
AND
NO
FLASHING
OF
THE
CEILING
INDICATORS,
3-3

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3,4
COND5NSgD
SET-UP
INSTRUCTIONS
1.
TURN
OUTPUT
LEVEL
CONTROL
FULLY
CCW.
2.
SET
METER
SELECTOR
SWITCH
TO
"G.R.".
3.
FEED
NORMAL
PROGRAM
LEVEL
INTO
THE
INSTA-PEAK
II.
4.
SET
THE
GAIN
REDUCTION
CONTROL
FOR
NORMAL
COMPRESSION
(5
TO
10
DB)
AS
INDICATED
BY
THE
METER.
5.
TURN
INPUT
CONTROL
CLOCKWISE
UNTIL
PEAK
CEILING
INDICATORS
JUST
BEGIN
TO
LIGHT
DIMLY
ON
PROGRAM
PEAKS.
. .
6.
TURN
THE
OUTPUT
CONTROL
CLOCKWISE
UNTIL
THE
DESIRED
OUTPUT
LEVEL
IS
OBTAINED.
NOTE:
IF
PEAKS
EXCEED
THE
DESIRED
MAXIMUM
LEVEL
THE
OUTPUT
SHOULD
BE
DECREASED
AND
THE
INPUT
LEVEL
CONTROL
INCREASED
TO
PROVIDE
TIGHTER
CLAMPING
LIMITS.
THIS
WILL
BE
INDICATED
BY
INCREASED
PEAK
CEILING
LAMP
INTENSITY.
HOWEVER,
EXCESSIVE
CLAMPING
SHOULD
BE
AVOIDED
AS
.
IT
CAN
CAUSE
NOTICEABLE
DISTORTION.
7.
THE
BALANCE
CONTROL
MAY
BE
ADJUSTED
SLIGHTLY
FROM
THE
R~FERENCE
MARK
TO
OBTAIN
THE
MOST
PLEASING
FREQUENCY
BALANCE.
/
3-4

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SECTION
IV
THEORY
OF
OPERATION
4
1
1
GENERAL
THE
ELCOM
INSTA-PEAK
II
CONBINES
THE
ADVANTAGES
OF
AN
OPTI~~L
AUDIO
ATTENUATOR,
SPLIT
SPECTRUM
CONTROL
AND
ABSOLUTE
PEAK
~EILIN~
TO
PROVIDE
AN
AUTOMATIC
LEVEL
CONTROL
SYSTEM
WHICH
CAN
"eAsILY
PRODUCE
OVER
20
DB
OF
CONTROL
WITHOUT
THE
EFFECTS
OF
:,,•ft
,.
PUMPJ~G
AND
AUDIBLE
DISTORTION
THAT
IS
CHARACTERISTIC
.
OF
OTHER
,',\\\
GAIN
~.
~ONTROL
DEVICES
OR
PROCESSORS.
AN
UNIQUE
"ANTI-RING"
CIRCUIT
PREVENTS
OVER-MODULATION
CAUSED
BY
OVER-SHOOT
AND
RINGING
WITHIN
THE
FM
EXCITER.
4.2
INPUT
LEVEL
CONTROL
CIRCUITRY
(SfE
FIGURE
4.1)
THE
INPUT
SIGNAL
IS
APPLIED
THROUGH
A
PAD
AND
TRANSFORMER
Tl
WHICH
SUPPLIES
SIGNAL
VOLTAGE
BY
WAY
OF
THE
OPTICAL
AND
MANUAL
ATTENUATORS
TO
FREQUENCY
SELECTIVE
AMPLIFIERS
Al
AND
A2.
Al
AMPLIFIES
FREQUENCIES
BELOW
l00HZ.
THE
PASS-BAN~
FREQUENCY
ROLL-OFF
FOR
THE
AMPLIFIER
IS
VERY
GRADUAL
TO
PREVENT
PHASE
DISTORTION
IN
THE
CROSS
OVER
AREA.
BALANCE
CONTROL
RS
IS
NORMALLY
I '
SET
~
~R
FLAT
FREQUENCY
RESPONSE,
BUT
CAN
BE
OFFSET
TO
BOOST
THE
HIGH
\
9R
LOW
FREQUENCY
PORTION
OF
THE
AUDIO
SPECTRUM.
THE
PEAK
CEIL!~G
CIRCUIT
CONSISTS
OF
TWO
LIGHT
EMITTING
DIODES
CONNECTED
BACK
JO
BACK
TO
PROVIDE
INSTANTANEOUS
LIMITING
OF
THE
AUDIO
PEAKS
THAT
MAY
PASS
THROUGH
THE
OPTICAL
ATTENUATOR
BEFORE
THE
PHOTO
CONDUCTIVE
CELL
CAN
RESPOND.
THE
PANEL
MOUNTED
L.E.D.'S
ALSO
GIVE
A
/
VISUAL
INDICATION
OF
PEAK
LIMITING. A
DIODE
SWITCHED
INTEGRATING
CIRCUIT
IS
USED
IN
CONJUNCTION
Wl~H
THE
PEAK
CEILING
L.E.D.'S
TO
ELIMINATE
WAVE
FORM
HARMONICS
WHICH
CAN
CAUSE
RINGING
AND
OVER-
MODULATION
FROM
FILTERS
AND
PRE-EMPHASIS
NETWORKS
WITHIN
THE
EXCITER.
4-1

www.SteamPoweredRadio.Com
THE
INPUT
LEVEL
AND
GAIN
REDUCTION
CONTROLS
ARE
SET
FOR
LIMITING
PEAKS
NOT
CONTROLLED
BY
THE
OPTICAL
ATTENUATORS.
OUTPUT
AMPLIFIER
AS
PRODUCES
AN
OUTPUT
OF
+22
DBM
BEFORE
CLIPPING
OR
AMPLIFIER
OVER-
LOAD
OCCURS,
A
PRE-EMPHASIS
IS
DEVELOPED
IN
AMPLIFIER
A7
BY
MEANS
OF
THE
FEED
BACK
NETWORK.
CORRESPONDING
DE-EMPHASIS
IS
SIMULIARLY
APPLI~9,
TO
AMPLIFIER
AB,
HIGH
FREQUENCY
GAIN
REDUCTION
AMPLIFIER
A3
11/'
INCORB9RATES
PRE-EMPHASIS
IN
ORDER
TO
INCREASE
GAIN
REDUCTION
OF
THE
,,,
,
\'I
I,
HIGHE,ij
,
FREQUENCIES
•
.
,,%
AUTOMATIC
GAIN
CONTROL
IS
ACCOMPLISHED
BY
THE
VOLTAGE
,1
..
,_"':
.
DIVID~R
·Acr10N
OF
THE
PHOTO-CONDUCTIVE
CELLS
IN
THE
OPTICAL
ATTENUATORS
IN
COMBINATION
.
WITH
RESISTORS
Rl
AND
R2.
L.E,D.'S
ARE
USED
A~
A
LIGHT
~OURCE
FOR
THE
OPTICAL
ATTENUATORS.
AMPLIFIERS
A3
AND
A4
RECEIVE
INPUT
SIGNAL
VOLTAGE
FROM
THE
GAIN
REDUCTION
CONTROLS
R4A
AND
R4B
AND
DRIVE
CONTROL
AMPLIFIERS
AS
AND
A6,
WHOSE
OUTPUTS
ARE
RECTIFIED
AND
APPLIED
TO
THE
L.E.D.
LIGHT
SOURCES
IN
THE
OPTICAL
ATTENUATORS.
THE
RECTIFIER
OUTPUT
ALSO
OPERATES
THE
GAIN
REDUCTION
INDICATOR.
THE
OUTPUT
OF
AMPLIFIERS
A5
AND
A6
IS
CROSS
CONNECTED
TO
THE
IDENTICAL
POINTS
IN
THE
COMPANION
INSTA-PEAK
II
WHEN
THE
STEREO
INTER-CONNECTION
IS
USED,
:t
·I
4-2

www.SteamPoweredRadio.Com
SECTION
V
MAINTENANCE
AND
REPAIR
511
GENERAL
THE
INSTA-PEAK
11
IS
AN
ALL
SOLID
STATE
DEVICE,
INCLUDING
THE
INDICATOR
LIGHTS.
NORMAL
ROUTINE
MAINTENANCE
IS
NOT
REQUIRED,
OTHER
THAN
POSSIBLY
AN
OCCASIONAL
PE.RFORMANCE
CHECK
TO
INSURE
THAT
THE
EQUIPMENT
IS
OPERATING
WITHIN
·
SPECI~ICATLONS.
~.2
ACCESS
TO
INTERNAL
COMPONENTS
'
THE
COMPONENTS
ARE
ACCESSIBLE
BY
REMOVING
THE
TOP
COVER
OF
THE
'
INSTA-PEAK
II
MODULE.
,
THE
BOTTOM
COVER
CAN
BE
REMOVED
TO
EXPOSE
THE
BOTTOM
OF
THE
CIRCUIT
BOARD.
513
TROUBLE
SHOOTING
METHODS
MOST
MALFUNCTIONS
CAN
BE
LOCATED
BY
_
USING
A D.C.
VOLTMETER.
READINGS
OF
A
DIGITAL
VOLTMETER
OR
VTVM
SHOULD
FALL
WITHIN
10\
OF
THE
TYPI~AL
VOLTAGES
LISTED
IN
TABLE
5.1
OF
THIS
SECTION.
AUDIO
VOLTAGE
CAN
BEST
BE
CHECKED
BY
USE
OF
·
AN
OSCILLOSCOPE.
5,4
CHECK
OF
BALANCE
CONTROL
SETTING
THE
FRONT
PANEL
BALANCE
CONTROL
SHOULD
BE
SET
TO
PROVIDE
AN
OVER
ALL
FLAT
FREQUENCY
R~SPONSE
WHEN
THE
RED
INDICATOR
MARK
ON
THE
CONTROL
DIAL
COINCIDES
WITH
THE
RED
MARK
ON
THE
PANEL.
THIS
SETTING
CAN
BE
CHECKED
~y
ALTERNATELY
APPLYING
AN
EQUAL
LEVEL
TONE
OF
100
HZ
AND
10,000
HZ.
THE
INSTA-PEAK
II
OUTPUT
SHOULD
REMAIN
THE
SAME
FOR
EITHER
TONE.
THE
GAIN
REDUCTION
CONTROL
SHOULD
BE
SET
FULLY
COUNTER-CLOCKWISE
DURING
THIS
TEST.
IF
THE
SETTING
SHOWS
A
LARGE
VARIANCE,
CHECK
FOR
DEFECTIVE
COMPONENTS
IN
THE
FREQUENCY
SELECTIVE
FEED-BACK
NETWORK
OF
AMPLIFIERS
Al
AND
A2.
5-1

www.SteamPoweredRadio.Com
515
ADJUSTMENT
OF
GAIN
REDUCTION
METER
ZERO
THE
FRONT
PANEL
METER
POINTER
SHOULD
RETURN
TOO
VU
(AT
THE
BEGINNING
OF
THE
RED
BAND),
WHEN
NO
GAIN
REDUCTION
IS
PRESENT.
VARIATION
CAN
BE
CORRECTE~
BY
ADJUSTING
THE
TRIM
POT
LOCATED
ADJACENT
TO
OUTPUT
TRANSFORMER
T2
ON
THE
MAIN
CIRCUIT
BOA~P.
5-2
/

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