McIntosh MR65B User manual

FMSTEREO
TUNER
MR65B
INTRODUCTION
TABLEOFCONTENTS
TECHNICALDESCRIPTION.
FRONTPANELINFORMATION
BACKPANELINFORMATION
INSTALLATION
CONNECTING
StereophonicFMMultiplex
MonophonicFM
RemoteAmplifiers
Off-The-AirRecording
AntennaConnections
OPERATINGINSTRUCTIONS.
StereophonicFMMultiplex
MonophonicFM
ExternalStereo
ADJUSTMENTS
MutingThreshold
FMSignalStrengthMeter
FMTuningMeter
DialPanelLights.
OutputAdjust
GUARANTEE
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MR65BFMSTEREOTUNER
INTRODUCTION
TheMclntoshModelMR65Bisa precision-
engineered,sensitiveFMmultiplexstereo
tuner.Itoffersthefinestpossiblereception
ofFMmonophonicandFMmultiplexstereo-
phonicbroadcasts.Everydesirablefeature
foryourFMlisteningpleasureisincludedin
theMR65Btuner.Itisperfectforuseina
stereomusicsystemwherenothinglessthan
"THEBest"willdo.
Onceyouhaveenjoyedtheoutstanding
performanceoftheMR65B,youwillunder-
standwhyMclntoshproductshaveearned
theirreputationas"THEBest."
YourMclntoshMR65Btunerwillgiveyou
yearsofthefinestpossibleFMreception,and
willbecomea highlyvaluedpartofyour
homemusicsystem.
TECHNICALDESCRIPTION
TheMR65Btunerhasa 6DS4high-gain
NuvistorforthefirstRFamplifier.TheNuvis-
tor(triode)operatesintoa triodetubetoform
acascodeamplifier.Carefuldesignofthe
operatingcharacteristicsallowsthecascode
amplifiertohandlea widedynamicrangeof
signalswithexcellentsignal-to-noiseratio.
Adouble-tunedRFinputcircuitcombined
withtheNuvistor-tubecascodeamplifier
reducesspurioussignalstoanextremelylow
value.Sensitivityisincreasedtothehighest
possiblerating,whilestillretaininghigh
selectivity.
AnewlydevelopedAutomaticFrequency
Control(AFC)circuitgreatlysimplifiestuning.
Asthetuningknobismoved,theAFCcircuit
automaticallycutsoffforsharpesttuning.
Afterthestationistunedin,theAFCcircuit
graduallycomesintooperationovera 3 sec-
ondinterval.TheAFCactionautomatically
bringstheelectricaltuningtothecorrect
pointforminimumdistortion.Thisauto-
matictuningrepeatsitsactioneachtimethe
tuningdialismovedtoa differentstation.
TheamountofAFCactionisfullyadjustable
witha frontpanelcontrol.
TheAFCcircuitisquiteunique.Itusesa
silicondiodeinplaceofa conventionaltube.
ThesilicondiodeimprovestheoverallAFC
performancesinceitisunaffectedbytem-
peraturechanges,hasnowarm-updriftand
eliminatesthechanceoftubefilamenthum.
Aspecialtemperature-compensatednarrow
banddetectorsuppliesoperatingsignalsto
theAFCcircuit.ThisinsurespositiveAFC
action.Thenarrowbanddetectoralso
operatestheFMtuningmeteramplifierand
theultrasonicmutingcircuit.
-TheMclntosh-developedultrasonicmuting
circuitautomaticallysuppressesallinter-
stationnoise,includingthenoisesusually
heardtuninginandoutofa station.Weakor
distantstationsthatdon'tover-ridetheback-
groundnoiseandinterferencearealsosup-
pressedbythemuting.A switchonthefront
panelallowsmutingtobecutoffforlistening
totheseweakandnoisystations.A back
paneladjustcontrolisfactory-settothe
propermutingthresholdlevel.
Threeflat-toppedresponseIFamplifiers
rejectadjacentchannelinterference.More
thanadequategainisprovidedtooperate
bothlimitersontheweakestsignals.Two
completelimitersareusedtoinsurethebest
possiblesignal-to-noiseratio.
Aseparatewidebanddetectorhandles
exclusivelytheaudiofrequenciesforlowdis-
tortionandwidefrequencyresponse.
BoththeRFandIFcircuitsarecom-
pletelyshieldedandexceedtheFCCrequire-
mentsforsuppressionofradiationfromthe
FMoscillatorandIFfrequencies.
Auniquemultiplexstereo(MPX)indicator
lightisincludedonthefrontdialpanel.The
MPXindicatorlightswheneverthedial
pointercrossesa stationbroadcastingFM
multiplexstereo.Theindicatorusesa special
noise-rejectingbridgecircuitwithtwoger-
maniumdiodes.TheindicatorlightsONLYon
the19KCcarrierpresentina multiplexstereo
broadcast.Itwillnotlightonnoiseorinter-
ferencesignals.
TheMR65Bmultiplexdecodercircuit
usesa specialpeak-switching,self-matrixing
detector.Stereochannelseparationismain-
tainedatbetterthan30db.
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Twopairsofaudiooutputjacksareonthe
backpanel.Onepairofjacksiscontrolled
onlybythefrontpanelvolumecontrol.The
otherpairofjacksiscontrolledonlybythe
backpaneloutputadjustcontrols.Twostage
feedbacktypepreamplifiersonbothchan-
nelsprovidelowimpedanceoutputs.More
thansufficientoutputvolumeisavailableto
feedpoweramplifiersaswellaspreamplifiers.
Anewtypeofmechanicaltuningassembly
givestheMR65Banextremelysmoothfly-
wheeltuningaction.Thetuningcapacitoris
drivendirectly,andinturndrivesthepointer.
Backlashispracticallyeliminatedwiththis
methodofdesign.A teflonlinedpointer
carriageandnylonpulleysreducefriction
andweartogiveanunusuallysmoothand
quietdialaction.
SPECIFICATIONS
UseableSensitivity
2.5microvoltsat100%modulation(±75KC
deviation)forlessthan3%totalnoiseand
harmonicdistortioninaccordancewithIHFM
standards.
AudioFrequencyResponse
Within½dbfrom20to20,000cycles.
Distortion
Lessthan0.5%at100%modulation±75KC
deviation.
CaptureRatio
1.5dbat100%modulation.
Muting
IFinjectedultrasonicmuting:atleast60db
noisereductionbetweenstations.
OscillatorDrift
Lessthan25KCwithAFCdisabled;negligible
withAFCinoperation.
ImageRejection
Betterthan80dbat90MC;betterthan70db
at105MC.
Hum
Betterthan70dbbelow100%modulation.
Output
Approximately2.5volts;lowimpedance.
AntennaInputs
300ohmsbalanced;75ohmsunbalanced.
RFAmplifier
Cascodewith6DS4Nuvistorinfirststage.
IFAmplifiers
Four,with200KCbandwidth,flattop
response
Limiters
Two
Radiation
SubstantiallybelowFCCrequirements.
MultiplexChannelSeparation
Betterthan30dbat1000cycles.
MultiplexFilter
Greaterthan48dbsuppressionof19KC
pilotand38KCcarrier.
MultiplexIndicator
Frontpanelmultiplexstereolightactivated
by19KCcarrier-only.
MultiplexType
Peak-detecting,self-matrixingdetector.
TubeandSemiconductorComplement
1—6DS4Nuvistor,1stRF.
1—12AT7,2ndRFandMixer.
1—6BN4A,Oscillator.
1—6AU6,1stIF.
1—6AU6,2ndIF.
1—6AU6,3rdIF.
1—6AU6,4thIFand1stLimiter.
1—6CS6,2ndLimiterandMuting.
1—6BN8,MutingAmplifier,MutingDetector,
AVCClamper.
2—6BL8,LeftandRight,1stand2ndAudio
Amplifiers.
1—12AU7,BalancedTuningMeterAmplifier.
1—6U8,MPXAmplifier,MPXIndicatorCon-
trol.
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1-12AU7,MPXOscillator.
1—ST2-275,VoltageReference.
1—MA113(Transistor),MPXIndicatorLamp
Switch.
2—Diodes,WideBandDiscriminator
2—Diodes,NarrowBandDiscriminator.
4—Diodes,BalancedMPXDetector.
2—Diodes,BalancedDetectorforMPXIndi-
cator.
2—Rectifiers,HighVoltagePowerSupply.
PowerConsumption
70watts,105to125volts,50to60cycles.
Dimensions
Frontpanel15-3/8inchesx 5-1/8inches;overall
depthofchassisbehindfrontpanel,12-3/16
inches;clearanceinfrontofmountingpanel
includingknobs,1-1/2inches.
Weight
Chassisonly,22pounds.
Inshippingcarton,31pounds.
FRONTPANELINFORMATION
Figure1.MR65BFrontPanel.
TUNINGDIAL
Thetuningdialiscalibratedinboth
megacyclesanda 0-100loggingscale.Tun-
ingbacktoa particularstationismucheasier
bykeepinga recordoftheexactstationloca-
tionontheloggingscale.
METERS
Figure2.FMSignalStrengthMeter.
AttheleftsideofthedialistheFMSIG-
NALSTRENGTHmeter.Theamountofmeter
pointerdeflectionindicatestherelativesig-
nalstrengthofthestationbeingreceived.
Usethesignalstrengthmetertocorrectly
positiona directionalFMantenna.Maximum
meterdeflectionfora particularstation
occurswhentheantennaispointedinthe
directionforbestsignalpickup.
Figure3.FMTuningMeter.
AttherightsideofthedialistheFMTUN-
INGmeter.AnFMstationiscorrectlytuned
whenthemeterpointeriswithintheblack
areaatthecenterofthemeterscale.Both
meterscanbeadjustedforproperzeroset-
tingsifnecessary.(SeesectiontitledAD-
JUSTMENTS.)
MULTIPLEXSTEREOINDICATOR
At thecenterof thetuningdialis the
multiplexstereo(MPX)indicator.Theindi-
catorlights(red)MPXwheneverthedial
pointercrossesa stationbroadcastingmulti-
plexstereo.TheindicatorlightsONLYonthe
19KCmultiplexcarrierpresentina multi-
plexstereobroadcast.Theindicatorwill
NOTlightonnoiseorinterferencesignals.
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VOLUME
Controlstheoutputvolumelevelofthe
tunerattherighthandpairofAUDIOOUT-
PUTjacksonthebackpanel.Thispairof
jacksismarkedFRONTPANELCONTROLLED.
Theotherpairofaudiooutputjacks,located
totheleft,isnotaffectedbythefrontpanel
volumecontrol.Theoutputvolumelevelat
thesejacksiscontrolledbythedualcon-
centricOUTPUTADJcontrolstotheirleft.
(Seesection titled ADJUSTMENTS.)
MODESELECTOR
AUTOFREQCONTROL
Figure4.ModeSelector.
PowerOff
TurnsoffthetunerACpowerandalsoturns
offtheACoutletonthetunerhackpanel.
IfaTVantennaisusedforFMintheman-
nerdescribedunderANTENNACONNEC-
TIONS,itwillautomaticallybeswitchedback
totheTVsetinthePOWEROFFposition.
FM
ProvidesmonophonicFMatbothpairsof
leftandrightchannelaudiooutputjacks.
MPXStereo
ProvidesFMmultiplexstereoattherespec-
tiveleftandrightchannelaudiooutputjacks.
EXTStereo
ProvidesmonophonicFMattheRIGHT
channelaudiooutputjacks.Thebackpanel
EXTSTEREOINPUTjackisalsoconnected
throughthetunerpreamplifiertotheLEFT
channelaudiooutputjacksinthisswitch
position.A monophonicAMtuner,forexam-
ple,maybeconnectedtotheEXTSTEREO
INPUTforAM-FMstereoreception.
Figure5.AutoFreqControl.
TheAutomaticFrequencyControl(AFC)
circuitmakesFMtuningeasier.Italsoelimi-
natesthepossibilityofthetunerdriftingoff
thestation.TheAFCcircuitintheMR65Bis
electronicallydelayedinitsaction.Thisisan
exclusiveMclntoshdevelopment.Asthe
tuningdialismoved,theAFCcircuitistem-
porarilycutoff.Afterthedialpointerhas
cometorestona particularstation,theAFC
graduallycomesintooperationovera three
secondinterval.TheAFCautomaticallybrings
theelectricaltuningtothecorrectpointfor
minimumdistortion.Thisautomatictuning
repeatsitselfeachtimethetuningdialis
movedtoa differentstation.
ThedegreeofAFCactionisadjustable
withtheAUTOFREQCONTROL.Fullleft
(MIN)positionofthecontrolcutsoffAFC
action.Fullright(MAX)positiongivesmaxi-
mumAFCaction.
Normally,thebesttuningoccurswiththe
AutoFreq.ControlsetatornearMAXposi-
tion.Ifseveralstationsareverycloseto-
gether onthedial,orifa desiredstationis
veryclosetogetheronthedial,orifa desired
stationisveryclosetoa muchstrongersta-
tion,a lowerAFCsettingisusuallynecessary
forbesttuning.
MUTING
Figure6.MutingControl.
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In
TurnsontheMclntosh-developedultrasonic
mutingcircuit.Ultrasonicmutingsuppresses
allbackgroundhissandnoiseandnoise
usuallyheardwhentuningbetweenstations.
Weakordistantstationsthatmaynotover-
ridethenoiseandinterferencearealsosup-
pressedbythemuting.
Out
Turnsofftheultrasonicmutingtoallowcon-
ventionalFMtuningwithinter-stationnoise
present.Usethissettingtolistentoweakor
distantstationsthatmaybemixedwith
noiseorinterference.
BACKPANELINFORMATION
Figure7.MR65BBackPanel.
TP2
Atestpointprovidedforconvenienceof
tunercircuitalignment.RefertotheMR65B
MaintenanceManualforcompletealignment
procedureandsuggested testequipment.
OUTPUTADJ
Dualconcentriccontroladjuststheoutput
volumelevelsatthelefthandpairofAUDIO
OUTPUTjacks.Thecentershaftadjuststhe
LEFTchanneloutput,andtheoutersleeve
adjuststheRIGHTchanneloutput.These
outputcontrolsettingsfortheleftpairof
jacksarenotaffectedbytheMR65Bfront
panelvolumecontrol.(Seesectiontitled
ADJUSTMENTS.)
MUTINGADJ
Adjuststheoperatingthresholdofthe
ultrasonicmutingcircuit.(SeeMUTING
ADJUSTunderADJUSTMENTSsection.)
AUDIOOUTPUT-LEFT-RIGHT
ThelefthandpairofAUDIOOUTPUT
jacksprovidesFMsignalsunaffectedbythe
MR65Bfrontpanelvolumecontrol.Thedual
concentricoutputadjustcontrolssetthe
volumelevels.Usetheseoutputjackstocon-
nectthetunertoa stereocontrolpreampli-
fierwhichhasitsownmastervolumecon-
trol.Thispairofjacksisrecommendedfor
Mclntoshpreamplifiers.
TherighthandpairofAUDIOOUTPUT
jacksprovidesFMsignalscontrolledbythe
MR65Bfrontpanelcolumecontrol.Use
theseoutputjackstoconnecttoexternal
poweramplifiers,taperecorders,orany
equipmentwhichrequirescontinuousfront
panelcontroloftuneroutputvolume.
EXTSTEREOINPUT
ConnectsthroughtheMR65Bleftchannel
preamplifierandappearsattheleftchannel
audiooutputswhentheMODESELECTORis
settoEXTSTEREO.TheMR65Bmonophonic
FMoutputappearsattherightchannelaudio
outputjackswhentheMODESELECTORis
settoEXTSTEREO.
AnAMtunermaybeconnectedtothe
EXTSTEREOINPUTforreceptionofAM-FM
stereointheEXTSTEREOsetting.
FMANT
TerminalsforconnectinganFMantenna
totheMR65B.
TOTVSET
TerminalsforconnectingTVsetantenna
leadswhena VHFTVAntennaisusedfor
boththeMR65Banda TVset.Theantennais
automaticallyswitchedtotheMR65Bwhen
the MODE SELECTOR switch turns the
MR65Btoanyofthe"ON"positions.The
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antennaisswitchedbacktotheTVsetwhen
theMR65BMODESELECTORisturnedto
POWEROFF.
1ASLOBLOFUSE
A1 amp"Slo-Blo"fuseprotectsthetuner
circuits.Thisfusedoesnotprotectadditional
equipmentconnectedtothebackpanel
ACoutlet.
ACOUTLET
Provides117voltACpowerupto350
wattsmaximumforadditionalequipment
suchasturntablesorothertuners.Thisout-
letisnotfusedandturnsonandoffwiththe
frontpanelMODESELECTORswitch.
PANELLIGHTSWITCH
Adjuststhefrontpanellightstobright
or dim.
INSTALLATION
TheMclntoshMR65Btunermaybein-
stalledona table,ona shelf,ina custom
built-incabinet,orina professionalequip-
mentrack.Forbestappearanceinanopen
installation,itissuggestedthatyoumount
theMR65BintheattractiveMclntoshModel
L66finishedwoodcabinet.
TheMR65Bmaybemountedinpanelsup
to1 inchinthickness.Ifthepanelisatleast
¼inchormoreinthickness,thetunerwillbe
adequatelysupportedbythefourfrontpanel
mountingscrews.Incaseswherethefront
panelmaybethinorflexible,a shelfisneces-
sarytosupporttheweightofthetuner.A
shelfisnotrequiredwhentheMR65Bis
mountedina metalrackpanel.
AnMR65Bcabinetinstallationshould
provideatleast13¾inchesbehindthe
mountingpanelforclearanceofleadsand
connectors.Allowinsidedimensionsofat
leastl6½inchesinwidthand5 inchesin
heightforadequateaircirculation.Theback
paneloftheMR65Bcabinetshouldbeleftas
openaspossibleforbestventilation.Avoid
mountingthetunerdirectlyovera power
amplifier.Theheatfromtheamplifieroutput
tubesmayaffecttheprecisiontunercalibra-
tion.Adequateventilationwillinsureyour
tunera longandtrouble-freelife.
CUTTINGTHEFRONTPANEL
ThePANELCUTOUTTEMPLATEsupplied
withyourtunerisa fullsizelayoutofthe
frontpanelcutoutandmountingholes.The
templateispositionedaccuratelyonthe
cabinetfrontbydrillingtwolocatingholes
throughfromthebacksideofthepanel.All
measurementsforpanelcutoutlocationare
madeonthebacksideofthepanel.Oneof
thetwoendmountingstripssuppliedwith
thetuner(3½inchesby½ inch)makesa
convenientmeasuringtoolfordetermining
theexactpositionsofthelocatingholes.
Determinetheexactcenterofthepro-
posedpanelcutoutarea.Scribea vertical
lineatthecenter,fromthetopsurfaceofthe
mountingshelftothetopofthepanelas
shownin"A"ofFigure8.Usingoneofthe
mountingstripsasa measuringtool,scribea
horizontalline3½inchesabovethetopsur-
faceofthemountingshelfasshownin"B"
ofFigure8.Againusingthemountingstrip,
marka pointonthehorizontalline3½inches
totheleftofthecenterline.Marka second
point3½inchestotherightofthecenter
line.Thesetwopointsshouldbe7 inches
apart,3½inchesabovethemountingshelf
and3½inchestoeachsideofthevertical
Positions"A"to"C"showthelocationofthe
verticalcenterline,theuseofthemeasuring
tool(mountingstrip)tolocatethehorizontal
centerline,andhowtomeasureoffthetwo
pointstotherightandleftoftheverticalcenter
line.
Figure8.FrontPanelCutoutMeasurements.
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centerline.See"C"ofFigure8.Drilla 3/16
inchdiameterholethroughthebackofthe
panelateachofthetwopoints.Makecertain
thatyouholdthedrillperpendiculartothe
panelsotheholeswillbeaccuratelylocated
onthefrontsideofthepanel.
Usingthepreviouslydrilledlocatingholes
forcorrectalignment,carefullypositionthe
cutouttemplateonthefrontpanel.
Scribetherectangularcutoutonthefront
panelandmarkthepositionsofthesix
mountingholes.Drillthesix3/16inchdiameter
mountingholesbeforecuttingthepanel
opening.Nextcutthemainpanelopening.It
isimportantthatthecutoutbejustwithinthe
heavyblacklinesonthetemplate.
SHELFMOUNTING
Locatetheexactcenteroftheproposed
shelfareaandscribea linefromthefrontto
thebackoftheshelf.TheSHELFCUTOUT
TEMPLATEismarkedforfrontpanelthick-
nessfrom¼ inchto1 inch.Foldthetemplate
onthelinethatcorrespondstothethickness
oftheparticularpanelbeingused.Placethe
foldedtemplateontheshelf,buttedagainst
thebacksideofthefrontpanel.Matchthe
centerlineonthetemplatetothescribed
centerlineontheshelf.Theshelfcenterline
shouldalsoexactlymeettheverticalcenter
lineusedtomakethefrontpanelcutout.
Markthepositionsofthefour¼ inchdiame-
termountingholes.Scribetherectangular
cutoutfortheventilatinghole.Drillthefour
¼inchdiametermountingholesandthen
cutouttherectangularventilatinghole.
INSTALLINGTHEMR65B
Removethefour10-32x % inchscrews
holdingtheMR65Btotheshippingboard.
Savethesescrewssinceyouwillneedthem
ifyourcabinetshelfis½ inchor5/8inchthick.
Removethefourplasticfeetfromthebottom
ofthetuner.
Themountinghardwarepackageincludes
four6-32flatheadscrewsandeight6-32
roundheadscrews.Twooftheflathead
screwsoftheproperlengthareusedtoat-
tachthemountingstripstothecabinetpanel.
Fouroftheroundheadscrewsoftheproper
lengthareusedtoattachthetunertothe
mountingstripsandthecabinetpanel.
The6-32x ½ inchscrewsareusedwith
panelsunder3/8inchthickness.The6-32x
1¼inchscrewsareusedwithpanelsfrom
3/8inchto1 inchthickness.
Theedgeofthestripwiththeclipsmust
facetowardthepanelopening.Lineupthe
mountingstripsoneachsideofthepanelcut-
outsothethreeholesinthestripsareinline
withtheholesinthepanel.Installtwoofthe
properlengthflatheadscrewsthroughthe
frontpanelandintothecenterholeofeach
mountingstrip.Drivethescrewsinsotheflat
headsareflushwiththepanel.Ifnecessary,
countersinkthetwocenterholes.
Figure9.SecuringtheMountingStriptoFrontPanel.
Carefullyinsertthetunerthroughthe
frontpanelopeningsoitrestsonthesup-
portingshelf.Inserttheproperlengthround
headscrewsintothefourholesinthemount-
ingflangesoneachendofthetunerpanel.
Drivethescrewsinthroughthepaneland
intothethreadedclipsonthemounting
strips.Donottightenthesescrewsyet.
Ifthecabinetisfixedandwillnotbe
movedabout,itisnotnecessarytosecure
thetunerchassistotheshelf.Ifthecabinet
istobemovedabout,itisrecommended
thatthetunerchassisbesecuredtothe
shelfinthefollowingmanner.
Tightenthefourscrewsholdingthetuner
tothefrontpanel.Thefour10-32x % inch
screwsusedinshippingthetunerarealso
usedtomountittoa shelfof½ inchor5/8
inchthickness.Usethe10-32x ½ inch
screwsifthemountingshelfis3/8inchthick-
nessorless.Usethe10-32x 1 inchscrewsif
theshelfis¾ inchor7/8inchthickness.
Securethechassiswiththeproperlength
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10-32screwsbyinsertingthemupthrough
theholesintheshelf,andintothethreaded
holesinthetunerchassisbottom.Tighten
the10-32screwsafteryouhavefirsttight-
enedthefrontpanelscrews.
IMPORTANT
Useofthewronglength10-32
screwsmaycauseelectricalshort-
inginthetunercircuits.
Attachthetwometalpanelend caps
(packedwiththetuner)oneachend ofthe
tunerpanelbyslidingontothepins.(See
Figure10.)Theendcapsareheldbyspring
tensionandcaneasilyberemovedifthe
tuneristobetakenoutofthecabinet.
MOUNTINGINTHEL66CABINET
TheMclntoshL66cabinetissupplied
withcompleteinstructionsandallnecessary
hardwareforinstallingtheMR65Btuner.The
PUSHON
Figure10.FittingofPanelEndCapstoPanel.
dimensionsoftheL66cabinetare169/16
incheswideby6-11/16incheshighincluding
mountingfeetby13¾inchesdeepincluding
tunerfrontpanelandcontrolknobs.
CONNECTING
UsethelefthandpairoftunerAUDIO
OUTPUTjacksforconnectingtoa conven-
tionalstereophoniccontrolpreamplifier.The
outputvolumelevelsatthesejacksare
affectedonlybythetunerbackpaneldual
concentricOUTPUTADJcontrols.Theleft
handpairofjacksisrecommendedwhenthe
tunerisusedwitha Mclntoshcontrolpre-
amplifier.
UsetherighthandpairofAUDIOOUT-
PUTjackswhenyouwishtousethetuner
frontpanelvolumecontrol.Usethesejacks
forconnectingdirectlytotaperecorders,
poweramplifiersoranyequipmentwithout
itsownvolumecontrol.
Thereisnodifferenceinthesignalquality
oravailableoutputlevelateachpairofout-
putjacks.
STEREOPHONICFMMULTIPLEX
Connecta shieldedcablefromtheproper
tunerLEFTchannelAUDIOOUTPUTjack,
tothecontrolpreamplifierLEFTchannel
tunerorauxiliaryinputjack.
Connecta secondshieldedcablefromthe
properRIGHTchanneltunerAUDIOOUTPUT
jacktothecorrespondingcontrolpreampli-
fierRIGHTchanneltunerorauxiliaryinput
jack.
Suitableshieldedcablesaresupplied
withthetuner.
MONOPHONICFM
Connecta shieldedcablefromtheproper
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tunerleftorrightaudiooutputjacktothe
monophoniccontrolpreamplifiertuneror
auxiliaryinputjack.WiththetunerMODE
SELECTORsettoFM,themonophonicFM
signalappearsatBOTHtheleftandright
channelAUDIOOUTPUTjacks.
REMOTEAMPLIFIERS
Thetwo AUDIOOUTPUTjacksnotbeing
usedinaninstallationmaybeconnectedto
externalorremoteamplifiers.FMprograms
canthenbefedtospeakerlocationsapart
fromthemainsoundsystem.
OFF-THE-AIRRECORDING
Taperecordersortapedeckswithrecord-
playbackpreamplifiersarenormallycon-
nectedtotheTapeOutputjacksonthecon-
trolpreamplifier.AnyFMprogramcoming
fromthetunerintothepreamplifiercan
thenberecordedontape.Youmayalsocon-
necttheextrapairoftuneraudiooutput
jacksdirectlytotherecorderinputsifdesired.
ANTENNACONNECTIONS
SatisfactoryFMmultiplexstereoreception
requiresapproximately10timesasmuch
signalfromtheantennacomparedtoequiva-
lentFMmonophonicreception.Monophonic
installationsthatweresatisfactorywithan
indoorFMantennamayrequireanoutsideor
directionalFMantennaforequivalentFM
multiplexreception.
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Figure11.MR65BTypicalHook-up.
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INDOORFLEXIBLEFMDIPOLE
300OHMINDOOR
DIPOLEFMANTENNA
Figure12.Connectionof300OhmIndoor
DipoleFMAntennatoMR65B.
Aconvenientflexibleindoordipole(300
ohm)antennaissuppliedwiththeMR65B
tuner.Thisantennaiseasytoinstallandis
suitableforgoodFMreceptioninurbanor
highintensitysignalareas.
Connectthetwoleadsofthedipolean-
tennatothetwo terminalsmarkedFMANT
onthetunerbackpanel.Theflexibilityofthe
thinflatwireallowsthedipoletobeeasily
locatedbehindtheequipmentenclosureor
inanyconvenientpositionnearthetuner.
Openthedipoleinto"T"andextendthe
armsasstraightaspossible.Thedipole
antennaissomewhatdirectionalandmay
havetobepositionedina particularlocation
forbestreceptionofdesiredstations.
IMPORTANT
Keepthedipoleawayfromlarge
metalobjectsorsurfacessince
theymayinterferewiththeeffi-
ciencyoftheantenna.
OUTDOORFMANTENNA
AnoutdoorFMantennaisalwaysrecom-
mendedforbestFMreceptionunderall
conditions.Infringeoroutlyingareasespe-
cially,a highlydirectionalFMantennaused
inconjunctionwitha rotatorwillgivethe
finestpossibleFMreception.Rotatethe
antennauntilitpointsinthedirectionofthe
stationoruntilitreceivesthebestpossible
signal.
TheFMsignalstrengthmeteraidsin
positioninga directionalantenna.Observe
themeterindicationfora givenstationasthe
antennarotates.Themeterwillindicateits
highestreadingwhentheantennaispointed
inthedirectionformaximumsignalpickup.
75OHMANTENNA
FROMVHFTV
ANTENNA
TO TV SET
Figure13.Connectionof75OhmAntennatoMR65B.
Anunbalanced75ohmFMantennamay
alsobeusedwiththeMR65B.Connectthe
centerleadofthecoaxiallead-incabletothe
righthandFMANTterminal.Connectthe
shieldofthecoaxialcabletotheground
screwnexttothissameFMANTterminal.
VHFTVANTENNA
Figure14.VHFTVAntennaConnections.
AconventionalVHFTVantennaofthe
typealsosuitableforFMmaybeusedwith
theMR65B.Connectthetwoleadsfromthe
300ohmTVantennalead-inwiretothetwo
FMANTterminalsonthetunerbackpanel.
Connecta lengthof300ohmflatlead-inwire
fromtheTOTVSETterminalsonthetuner
backpaneltotheantennaterminalsofthe
TV set.
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OPERATINGINSTRUCTIONS
STEREOPHONICFMMULTIPLEX
1.TurntheMODESELECTORtoMPXSTEREO.
2.TurntheAUTOFREQcontroltoMAX.
AutomaticFrequencycontrolcorrectsthe
electricalstationtuningtotheexactpointfor
minimumdistortion.Anelectronicdelay
turnsontheAutomaticFrequencycontrol
overa 3 secondintervalafterthedialpointer
stopsona station.Forallnormaltuning,set
theAUTOFREQCONTROLtoMAX.
Ifstationsareclosetogetheronthedialor
ifa desiredstationisclosetoa muchstronger
station,reducetheAUTOFREQCONTROL
settingforbesttuning.
3.TurnMUTINGtoIN.
MclntoshUltrasonicmutingsuppresses
allbackgroundnoiseandhissusuallyheard
whentuningbetweenstations.UseMUTING
INforallnormaltuning.
Weakordistantstationsthatdon'tover-
ridethebackgroundnoiseandinterference
arealsosuppressed.TurnMUTINGOUT
tolistentotheseweakerstations.
4.TurntheFMTUNINGdialtothedesired
station.Thetuningmetershouldindicate
inthecenterblackarea.IftheredMPX
indicatorlights,thestationisbroadcasting
multiplexstereo.TheMPXindicatorlights
ONLYwhenthetunerisreceivinga station
broadcastingFMmultiplexstereo.The
indicatorwillNOTlightonnoiseorinter-
ferencesignals.
Ifthesamestationbroadcastsa regular
monophonicFMprogram,theMPXindicator
willremainoff.
5.Adjusttheappropriatevolumecontrols,
dependingonwhichpairofAUDIOOUT-
PUTjacksisbeingused.
ThefrontpanelVOLUMEcontroloperates
onlywiththepairofAUDIOOUTPUTjacks
markedFRONTPANELCONTROLLED.Set
theVOLUMEcontroltoitsmidposition.
TheOUTPUTADJcontrolsontheback
panelpre-setthevolumelevelsoftheleft
handpairofAUDIOOUTPUTjacks.Turnthe
outerknurledsleeveforRIGHTchannel
volumeandthecenterknurledshaftforLEFT
channelvolume.SettheOUTPUTADJcon-
trolstotheirmidpositions.Makefinalvolume
adjustmentstobalancethetunervolume
withthevolumeofa phonorecordplaying
throughthecontrolpreamplifier.
MONOPHONICFM
1.TurntheMODESELECTORtoFM.
2.TurntheAUTOFREQCONTROLtoMAX.
(AdjustthesameasforMPXreception.)
3.TurnMUTINGtoIN.
(SetthesameasforMPXreception.)
4.TurntheFMTUNINGdialtothedesired
station.Thetuningmetershouldindicate
inthecenterblackarea.
5.Adjusttheappropriatevolumecontrols,
dependingonwhichpairofAUDIOOUT-
PUTjacksis beingused.
(AdjustthesameasforMPXreception.)
EXTERNALSTEREO
1.Connectanexternaltunertotheback
panelEXTSTEREOINPUTjack.
2.TurntheMODESELECTORtoEXTSTEREO.
3.TurntheAUTOFREQCONTROLtoMAX.
(AdjustthesameasforMPXreception.)
4.TurntheFMTUNINGdialtotheFMsta-
tionbroadcastingonechannelofa stereo-
phonicbroadcast.Thetuningmetershould
indicateincenterblackarea.
(TheFMbroadcastappearsintheRIGHT
channel.)
5.Tunetheexternaltunertothestation
broadcastingtheotherchannelofthe
stereophonicbroadcast.(Theexternal
tunerprogramappearsintheLEFTchan-
nel.)TheEXTSTEREOfunctionwillmost
oftenbeusedforAM-FMstereophonic
broadcasts.Thestationbroadcastsone
channelofa stereoprogramontheAM
transmitterandtheotherchannelonthe
FMtransmitter.
6.Adjusttheappropriatevolumecontrols,
dependingonwhichpairofAUDIOOUT-
PUTjacksisbeingused.
(AdjustthesameasforMPXreception.)
Iftheexternaltunerhasa volumecon-
trol,adjustittoequalthevolumelevel
oftheMR65B.
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ADJUSTMENTS
MUTINGTHRESHOLD
TP2
MUTING
ADJ
OUTPUT
ADJ
MCINTOSHLABORATORYINC.
BINGHAMTON.N.Y.
MADEINUSA
Figure15.MutingThreshold
TheMR65Bultrasonicmutingcircuit
suppressesallnoisebetweenstations.Italso
suppressesallweakerstationsnotstrong
enoughtoover-ridethebackgroundnoise.
Themutingthresholdsettingdetermines
thestrengthofthesignalwhichcanbe
heardwithmuting inoperation.Themuting
thresholdiscarefullyadjustedtooptimumat
thefactoryusingprecisiontestinstruments.
Casualadjustmentofthemutingthreshold
isnotrecommended.
Ifitisfoundnecessarytoadjustthe
mutingthreshold,usetheMUTINGADJ
controlonthetunerbackpanel.Turnthe
MUTINGADJcontroltotheRIGHT(clock-
wise)tolowerthemutingthreshold.This
allowsweaker,noisierstationstobeheardat
theMUTINGINsetting.TurntheMUTING
ADJcontroltotheLEFT(counterclockwise)
toraisethemutingthreshold.Thisallows
onlythemorepowerfulstationstobeheard
attheMUTINGINsetting.
FMSIGNALSTRENGTHMETER
TheFMSIGNALSTRENGTHmeterpointer
shouldnormallyrestonthezeroscalemark-
ingwithFMoperatingbutnostationtunedin.
Figure16.FMSignalStrengthMeter
Toadjust,turntheMODESELECTORto
FM.TurntheMUTINGcontrolOUT.Turnthe
AUTOFREQcontroltoMIN.Thevolumecon-
trolhasnoeffectonthisadjustment.Turn
thetuningdialtoa positionNOTonorneara
station.Allowthetunertooperateforap-
proximately5 minutes.RotatetheredSIG
STHthumbwheelcontrol(undertheleftdial
panelendcap)untilthemeterpointeris
centeredonthezeroscalemarking.
FMTUNINGMETER
Figure17. FMTuningMeter.
TheFMTUNINGmeterpointershould
normallyrestwithinthecenterblackareaof
thescalewhenanFMstationisproperly
tuned.
Checkthetuningmeteradjustmentin
thefollowingmannerafterthetunerhas
beenoperatingapproximately5 minutes.
TurntheMODESELECTORtoFM.Turn
theAUTOFREQCONTROLtoMIN(counter-
clockwise).TheMUTINGandVOLUMEcon-
trolshavenoeffectonthisadjustmentand
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maybesetinanyposition.TunetoanFM
stationuntilthemeterpointerisexactlyin
thecenteroftheblackscalearea.Turnthe
AUTOFREQCONTROLtoMAX(clockwise).
Waita fewsecondsandwatchthemeter
pointertoseeifitmovesoffthecenterof
theblackscalearea.
Adjustthebrightnessofthedialpanel
lightsbymeansofthePANELLIGHTswitch
onthetunerbackpanel.Settheswitchto
BRIGHTformaximumpanellight.Setthe
switchtoDIMforlessdiallightandextended
lamplife.
Ifthemeterpointerchangesposition,
adjusttheredTUNINGMTRthumbwheel
control(undertherightdialpanelendcap)
untilthemeterpointermovesbacktothe
centeroftheblackarea.Checktheadjust-
mentbyrepeatingtheprocedure.Again
turntheAUTOFREQCONTROLbacktoMIN
andre-tunethestation.TurntheAUTO
FREQCONTROLuptoMAXandagaincheck
formeterpointer movement.Adjustthe
tuningmeterthumbwheelcontrolagainif
necessarytore-centerthemeterpointerin
theblackarea.Ifthemeterpointer movesan
appreciableamountonthefirsttest,the
secondadjustmentisnecessaryforprecise
meteroperation.Whenthemetercircuitis
properlyadjustedthemeterpointershould
staycenteredintheblackscaleareawhen
theAUTOFREQCONTROListurnedfrom
MINto MAX.
WhentheFMtuningmeterisadjustedby
thisprocedure,preciseFMtuningisinsured
withthemeterpointercenteredintheblack
scalearea.Thisprocedureeliminatesthe
possibilityofnoiseaffectingthemeter
adjustment.
DIALPANELLIGHTS
105-125V
50-60CPS
70WATTS
PANEL
LIGHT
OUTPUTADJUST
TP2
MUTING
ADJ
OUTPUT
ADJ
MclNTOSHLABORATORYINC
BINGHAMTONNY
MADEINUSA
Figure18.DialPanelLights.
Figure19.OutputAdjust
ThedualconcentricOUTPUTADJcon-
trols(onthetunerbackpanel)adjusttheout-
putvolumelevelofthelefthandpairof
AUDIOOUTPUTjacks.Thecentershaftof
thecontroladjuststheleftchanneloutput.
Theoutersleeveofthecontroladjuststhe
rightchanneloutput.
Toadjust,firstconnectthelefthand
AUDIOOUTPUTjackstothetunerinputsof
thecontrolpreamplifierbeingused.Setthe
preamplifierselectortophonoandthe
volumecontroltonormallisteninglevelfora
typicalstereodiscrecording.Switchthe
preamplifierbacktothetuner.Setthe
MR65BMODESELECTORtoFMandtunein
alocalstation.TurnthetunerOUTPUTADJ
controlsuntilthelevelsofeachchannelare
equaltoeachotherandalsoequaltothe
volumelevelofthepreviousphonorecord-
ing.Youcannowswitchthepreamplifier
selectorfromtheMR65Bto otherprogram
sourceswithoutneedforreadjustingthe
mainvolumecontrol.
13
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YourMclntoshMR65Btunerwillgiveyoumanyyearsofpleas-
antandsatisfactoryperformance.Ifyouhaveanyquestionscon-
cerningtheoperationormaintenanceofthistuner,pleasecontact
CUSTOMERSERVICE
MCINTOSHLABORATORYINC.
2CHAMBERSSTREET
BINGHAMTON,NEWYORK
Ourtelephonenumberis723-5491.
Thedirectdialareacodeis607.
GUARANTEE
MclntoshLaboratory,Inc.guaranteesthisequipmenttoper-
formasadvertised.Wealsoguaranteethemechanicaland
electricalworkmanshipandcomponentsofthisequipmenttobe
freeofdefectsfora periodof90daysfromdateofpurchase.
Thisguaranteedoesnotextendto componentsdamagedby
improperusenordoesitextendtodamageincurredduring
transportationtoandfromMclntoshLaboratory,Inc.
3-YEARFACTORYSERVICECONTRACT
Anapplicationfora FREE3-YEARFACTORYSERVICECON-
TRACTisincludedinthepocketinthebackcoverofthismanual.
TheFREE3-YEARFACTORYSERVICECONTRACTwillbeissued
byMclntoshLaboratoryuponreceiptofthecompletelyfilledout
applicationform.Thetermofthiscontractisdefinedinthe
3-YearFactoryServiceContract.Iftheapplicationisnotmailed
toMclntoshLaboratory,onlytheservicesofferedunderthe
standard90-dayguaranteewillapplyonthisequipment.TAKE
ADVANTAGEOF3 YEARSOFFREEFACTORYSERVICEBYFILL-
INGINTHEAPPLICATIONNOW.
InCanada:Manufacturedunderlicenseby:
McCurdyRadioIndustries,Ltd.
22FrontStreetWest
Toronto,Canada
14
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LABORATORYINC.
2CHAMBERSSTREET,BINGHAMTON,N.Y.
MadeinU.S.A.
Phone-AreaCode607-723-5491
1M-AA107-2369-15
PrintedinU.S.A.
www.eskonline.nl