IRT AA-342 User manual

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RT ELECTRONICS
PTYLTD
26HothamParade
ARTAR[ilONNS W
Phone:
llSD
Code6ll (02)
4393744Fa>
2064Australa
(02)
4397433TelexAA122130
AA-342
AUDIODISTRIBUTION
AMPLIFIER
BAt5L7 gL-46-i,.i8.2
DESIGNEDANDMANUFACTURED
IN AUSTRALIA

Sectlon
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J.
4.
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'7
AA-342
AUDIO
DISTRIBUTION
AMPTIFIER
INSTRUCTION
BOOK
Contents
General- Descriptlon
Technieal Data
Circuit Description
Maintenance
Instal-l-ation
Circuit Diagrams
Parts Lists
Page
-1
,
A
6
WARNINq
OPERATION OF ELECTRONIC
EQUIPMENT
INVOLVES
THE USE OF VOLTAGES
AI{D CI]RRENTS WHICH
}4AY
BE DANGEROUS
TO HUMAN LIFB, OPERATING
PERSONNBL SHOULD
OBSERVE
ALL SAFETYREGULATIONS. DO NOT CHANGE
COMPONENTS
OR MAKE
ADJUSTMENTS
INSIDE TFJBEQUIPMENT
WITFI
POWER
ON
IJNLESS
PROPER
PRECAUTIONS
ARB OBSERVED. NOTETFIAT
UNDBR CERTAIN
CONDIT]ONS DANGBROUS
POT'ENTIALS
MAY
EXIST IN SOME
CIRCIJITS EVEN
THOUGH
POWER
CONTROLS
ARE IN THE OF'tr''
POSITION.
BAL5L7

G:-NFRAL DESCP,IPTION
Tne h,I^,-342
Encoded Audio Distribution Amplifier is a wlde bandwidth
a-npl1fjer for distrrbut-ing comfosite encoded stereo signals. The
IJ.-342 is designed Lo isolate the audio ground cj-rcuit of transmitter
i-nrrr eoriinment fron the t::ansr,Litter oround circuit, in FM transmission
.vstems. To fulf :-l this function the desigrn of *.he AA-342 incorporates
w:de l ancwioth, low C
jstoi:tion a.ndinput comrlronnode rejectjon, Gain
i c ;-,irrret.:'hl
a ttw : '-r --1- r:ncl e
onLrol frorn +3dF to -1OdB.
-o l,een tho orrtrrrrf i-r.edance or the AJ',-342amplifier low 75 ohm
resistors are used to Cistribute the output signal. This ensures
.irat lonq cahJe runs will not cause a roll orf in the frequency response
-wiif.-.t still providrng short circuit protection for the amplifier.
Tre LA-342 is housed in an IRT *cinole width module which mounts in a
F-100D i-ack frane wlricb occuoies l34mnrof rack space.
Inpu-- and output connections are by BNC connecto::s and power connectlon
:s ti'n.ans of an >iL-i.NE
power socket all mounted on the module rear
asserjrllz.

-
2.
TECHNICAL DATA.
INPUT TTnhalanced inout imnedenee 5K ohm.
urrlqaqrrusq r rryuL
OUTpUT Three unbalanced 75 ohm source designed to be foaded
by high (lK ohm or greater) impedance loads.
GAIN Adjustable by front panel control from +3dB
1-o -tuofj.
COI1MON
MODE Ad;ustable by internaf controf. With input and
REJECTION output grounds isolated, better than 40dB at
5AHZ.
+
FREQLIENCY -0.5d8 in the range 2oHZ Lo 100KHZ
referenced to
RESPONSE lKHz.
i{AR,}4ONIC
DlSTORTION
Less than 0.5ea in the range 2OHZLo lOOKHz
at an
audio level of I volt rms at the output.
NOISE Less than -70d8 at the output bandwidth 2OHz Lo l5KHz
referenced to an output level of I volt rms.
PO}IER 240 volts at 2VA.
RIiQLTTRE\4ENTS
DII'1trNSIONS ll8rrirn x 41inm x 325mm.

3.
CIRCUIT DESCRIPTION
The AA-342 circuitry consists of two parts, an input amplifjer comprising
n'l fn o? :nd rn orrfnrrf emnlificr cnmnric'i nc C)4 tn OR The innrrt :mnlifipr
LU VJ vu Ll'u
is a djfferential input feed back amplifjer with unjty gain. Adjustment
of the comrnon-mode
hum rejection is rnade by VR2 the balance control.
Inductors LI,L2 and capacitors Cl9 to C22 comprise an RF fifter in the
input circujt. The output amplifjer is a complementary s1'mmetryemitler
follower feedback ampljfier with a gain of two. For correct operation
the DC voltage at the output as measured at the junction of Rl7, RIB
is set at +0.25 volts by adjustment of VR3 Lhe O/P DC control. Overall-
aain of fhc AA-?/1 :^ ^^! L" - cronf nancl nnttnted nntenfionefer VRl.
vuf,rr vr JaL !; >EL ty o J Lgu pvLsllLiulllsLs!
.Fn l.pon fhe o'rtn"+ :*^^,r--.^^ ^€ thc AA-342 arnnlifjer lOw 75 ohm fesjStors
are used t-o oistribute the output signal. This ensures that long cable
runs will not cause a ro11 off in the frequency response whilst still
rr-nvi6lir'6 c667t eirelit nrnter-tion for the amplifier,
OperaL:no voltaoes of 1t3 volts are supplied by the power supply comprjsjng
transiormer Tf and a half wave bridge rectifier D3 to D6 and C}, C2.

4
I.[AINTENANCE
If adjustment ol the cornmon-mode
hum rejectjon is required short the
inner and outer connections of the input BNC connector and appl!' a 50llz
sigmal source between these and case qround, Adjust the balance control-
\G.2 for minrmum hur' siqnal at the orrtnrrt- The DC voltaoe at the orrfnrrt
arnnri
ricr a. -..=,]'.; :;";..",;;".;";""; Rr7. ;,;-';;;=;"-=.;""."-"'*--,,- J
+0.25 volts by adjustment of the O/P control \rR3.
VOLTAGEI{EASURtrMtrNTS
EMITTER
+ 0.6v
+ 0.6v
-13 v
- 1) 'l\l
-13.4V
- 0.5v
+ 0.2v
+ 0.3v
BASE COLLECTOR
A11 measurements irLadewith a hiqh input i nneci;nce rrol imeter.
Q1
n?
AA
o5
Q€)
Q7
ttx
OV
-IJ V
OV
+ 0.5v
-f3 .4V
--LJ . '+V
+13
,4V
OV
/t]\ 7
- 0.47v
+ n qA\7

INSTALLATION
The AA-342 module is supplied with a slide tray, RB-53 rear assembly and
associated hardward for mountinq .in an F-100D frame.
\ | f da 't'r:rt
The slide is a shallow tray which supports the module in the frame,
ft is mounted on the front and rear cross members of the frarcLe
and
is fixed in pJacc with the steef clips (speed nut type) provided.
Porr Aqcomh]rr
The rear assembly is mounted on the rear of the frame wj"th the screws
provided. Care should be taken not to over tighten these screv;s,
as excessive force wjll damaoethe thread in t-he mounting frame.
Connections
-signal connections are b1' means of BNC sockets and power input by an
XL-LNE socket all nounted on the rear assernbly back plate.

ACCF,SSOIiIES
F-100D Modu1e Mounting F::ame:
-
Provides mounting for up to 10 moCules side by side
in 123mmof starrdard rack space.
(3 rack units) '
TME-] Module Extender:-
Fnables a module to be operated in position and provide
access to all circuit boards, transistors and internal-
:ulirrq1-manfq
RB-53 Rear Assembly: -
An addjtional rear assembly may be purchased to permit
bench testing and sen'icinq of the amplifier without
disturbrng the rear assemblies supplied with the
ampli
fiers.
INSTRUCTION
BOOK.

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