McIntosh MR65 User manual

STEREOFM
TUNER
MR65
TABLEOFCONTENTS
OWNER'SMANUAL
ISSUENO.2 ReadingTime30MinutesPrice$1.25
MR65
GENERALDESCRIPTION1
TECHNICALDESCRIPTION1
FRONTPANELFACILITIES2
DialScale2
Meters2
VolumeControl2
ModeSelector2
Auto.Freq.Control3
Muting3
BACKPANELFACILITIES3
ExternalMultiplex3
MutingAdjustment3
OutputJacks3
InputJacks3
AntennaTerminals4
Fuse4
INSTALLATIONINSTRUCTIONS4
CONNECTINGINSTRUCTIONS5
MonophonicFMPrograms5
StereophonicInternalMultiplex6
StereophonicExternalMultiplex6
StereophonicFM-FMorFM-AM6
AntennaConnections6
OPERATINGINSTRUCTIONS7
MonophonicFMPrograms7
Stereophonic—InternalMultiplex7
Stereophonic—ExternalMultiplex7
Stereophonic—FM-FMorFM-AM7
TapeRecording7
ADJUSTMENTS8
Meters8
DialLights8
GUARANTEE8

MR65STEREOTUNER
GENERALDESCRIPTION
Care,inthegreatestdegreehasbeendevotedonthis
tunerduringresearch,design,engineering,andmanu-
facture.Sothroughlyhaseverydetailofthisequipment
beenplannedandcarriedoutthatevenitsappearance
speaksofthequalityworkmanshipthatisusedthrough-
out.
OnceyouhavelearnedtousetheMR-65. . . expe-
riencedtheoperationofitscontrolsandmanyfunctions
.. . andhadtheopportunitytoevaluateitsperformance
.. . youwillunderstandhoweffectivelytraditionalMcln-
toshdesignandengineeringhavebeencombinedto
defeatobsolescenceandprovideyearsoftrouble-free
performance.
TheMR-65ishighlyflexibleinitsoperation.Itwill
receiveeithermonophonicorstereophonicFMbroad-
casts.A frontpanelvolumecontrolandtwo-stageaudio
amplifierallowtheMR-65tooperatethroughanytypeof
monophonicorstereophonicequipmentincludingpre-
amplifiers,poweramplifiers,taperecorders,etc.
Allprovisionshavebeenmadetoconnectanadapter
foranytypeofmultiplexsystemtheFederalCommunica-
tionsCommissionmayadoptasa resultoftheirpresent
investigationandseriesoftests.Mclntoshwillmanu-
facturea built-inmultiplexadapterdesignedtofitina
preparedchassisopening.Youcanconnectitwitha
minimumofeffort.Or,ifyouchoose,anexternalmulti-
plexadaptercanbeconnectedtothejackprovidedonthe
backpanel.
TECHNICALDESCRIPTION
TheMR-65RFtuningsectionusesa cascodeampli-
fier,speciallydesignedtoamplify"weaksignals"forless
noiseanddistortion.Threeflat-toppedIFamplifiers
rejectadjacentchannelinterference.Theygiveenough
gainforweaksignalstooperatethelimiters.Twocas-
cadedlimitersfurtherimprovethesignal-to-noiseratio.
A4-gangcapacitorandanadditionaltunedcircuitin-
creasesRFselectivity,reducingspuriousorunwanted
signals.
TheMR-65usestwotemperaturecompensateddis-
criminators.Oneisa narrow-banddiscriminatorusedfor
ultrasonicmuting,automaticfrequencycontrol,andtun-
ingmeterdrive.Thesecondoneisa broad-banddis-
criminatorthatgivesnearlyperfectaudioperformance.
Avariabie-capacitancesilicondiodeisusedintheAFC
circuitinsteadofa conventionaltube.Thesilicondiode
improvesAFCaction,isunaffectedbytemperature
changes,eliminatesfilamenthum,anddoesnotdrift
duringwarm-up.
ThenewlydevelopedAFCcircuitautomaticallyaids
tuning.Duringmanualtuning,theMR-65respondsasif
noAFCwereoperating.Whenmanualtuningiscom-
pleteda smalldifferenceusuallyremainsbetweenthe
lowestdistortionsettingandthemanualtuningsetting.
ThenewcircuitbringstheAFCintoactiongradually,
overapproximatelya threesecondinterval,toimprove
thetuningelectricallyandautomatically.Thisautomatic
advantageisrepeatedeachtimea stationistunedon
theMR-65.TheAFCiscompletelyvariablebya control
onthefrontpanel.
TheexcellentsoundqualityoftheMR-65istheresult
ofusinga two-stage,lowimpedance,feedbackaudio
amplifier.A frontpanelvolumecontrolpermitscon-
venientadjustmentofoutputlevel.
TheRFandIFcircuitsoftheMR-65arecompletely
shieldedandexceedtheFCCrequirementsforsuppres-
sionofoscillatorradiation.Eithera 300ohmor75ohm
antennamaybeusedwiththeMR-65.A VHFtelevision
antennawhichissuitableforFMreceptioncanbecon-
nectedtotheMR-65.Whenthetuneristurnedoff,it
switchestheantennabacktotheTVreceiver(seeAn-
tennaConnectingInstructions).
IntheMR-65,a newtypeofmechanicaltuning
assemblygivessmoothflywheeltuning.Withdirectdrive
tothetuningcapacitor,whichinturndrivesthepointer,
backlashisalmosteliminated.Forsmooth,quietaction
andextendedlifewithvirtuallynowear,a teflonlined
pointercarriageandnylonpulleysareusedinthedial
cordassembly.
ELECTRICALSPECIFICATIONS
USABLESENSITIVITY
3¼microvoltsat100%modulation(±75kc.)forless
than3%totalnoiseanddistortioninaccordancewith
IHFMStandards.
AUDIOFREQUENCYRESPONSE
Within2 dbfrom20-20,000cycles.
DISTORTION
Lessthan3%for100%modulation(accuracyofthebest
availabletestequipmentisnotguaranteedbelow3%).
CAPTURERATIO
1to0.7.
MUTING
Atleast60dbnoisereductionbetweenstations.
OSCILLATORDRIFT
Lessthan25kc.withAFCdisabled;negligiblewith
AFCinoperation.
IMAGEREJECTION
Betterthan80dbat90mc.;betterthan70dbat105mc.
HUM
Betterthan65dbbelow100%modulation.
OUTPUT
Approximately4 volts;lowimpedance.
ANTENNAINPUTS
300ohmsbalanced;75ohmsunbalanced.
POWERCONSUMPTION
75watts,105to125volts,50-60cycles.
TUBECOMPLEMENT
6BN4ARFAmplifier6SC62ndLimiter
6BN4AOscillator6BN8Squelchamplifier
andAGCClamp
12AT7Mixer6C4Meter
(3)6AU6IFAmplifiers6U8AAudioamplifier
6AU61stLimiterEZ80/6V4Rectifier
1

MECHANICALSPECIFICATIONS
DIMENSIONS
Frontpanel—155/8"by51/8".Overalldepthofchassis
behindfrontpanelis125/16"—Acabinetopening145/16"
by411/16"isrequiredtoinsertchassis(refertoTemplate).
WEIGHT
Chassisonly—21lbs.6 oz.Inshippingcarton—30lbs.
12oz.
AccessoriessuppliedwiththeMR-65include:
1.Instructionbook,
2.Templatesformounting,
3.FoldedDipoleAntenna,
4.6 ft.shieldedsignalcable,
5.Mountinghardware.
FRONTPANELFACILITIES
Fig.1—DrawingofMR-65frontpanelshowingallcontrols,dialandmeters.
DIALSCALES
TheMR-65dialhastwoscales.Thescale,belowthe
line,ismarkedinmegacyclesandthescale,abovethe
line,isa loggingscale.Theloggingscaleisusedto
accuratelyre-tuneanystation.Itisusuallyeasiertokeep
arecordofyourfavoritestationsbytheuseofthesimple
numbersontheloggingscale.
METERS
Inthedialassemblytherearetwometers.Themeter
ontherightistheTUNINGmeterandtheoneontheleft
istheSIGNALSTRENGTHmeter.
Astationiscorrectlytunedwhenthepointerofthe
TUNINGmetercomestorestanywhereintheblackarea
inthecenterofthemeterface.Themeterisdrivenby
thenarrow-banddiscriminator.Becausethemetermove-
mentismagneticallydampedthepointermayneed
adjustmenttothecenterofthescaleatthetimeof
permanentinstallation.Undertherightpanelendcapis
aredknobwitha decalbesideitmarkedTUNINGMETER.
ThisknobcenterstheTUNINGmeter.Properadjustment
isexplainedonpage8 under"MeterAdjustments."
TheSIGNALSTRENGTHmeterisdrivenbythe1st
IFAmplifierandindicatestherelativestrengthofsignal
fromeachstation.Tuningformaximumsignalstrength
ona weakstationassistsincorrecttuning.Ifa directional
FMantennawitha rotatorisusedtheSIGNALSTRENGTH
metercanindicatetheproperdirectionfortheantenna.
ThezeroadjustmentfortheSIGNALSTRENGTHmeter
istheredknobundertheleftendcapidentifiedbythe
SIG.ST.ADJ.decal.Properadjustmentisexplainedon
page8 under"MeterAdjustment."
VOLUMECONTROL
Thevolumecontrolpermitsadjustmentofthepro-
gramloudnessattheMONOOUTjacksontheback
panel.TheSTEREOOUTjacksarenotcontrolledbythe
frontpanelvolumecontrol.
MODESELECTOR
Fig.3-The4 positionMODESELECTORinthe
POWEROFFposition.
POWEROFF:
TheMR-65isoffwhentheswitchisturnedtothe
extremeleftorcounterclockwiseposition.TheA.C.out-
letonthebackpanelisalsoturnedoffbythisswitch.
InthePOWEROFFpositionanyaddedprogram
sourcepluggedintothejacksmarkedSTEREOINonthe
backpanelisconnecteddirectlytotheSTEREOOUT
jacks.Thispermitsanaddedprogramsourcetobe
playedthroughthesystemwithouttheMR-65being
turnedon.
Fig.2—VolumeControl.
Fig.4-MODESELECTORintheFMposition.
FM:
InthispositionallmonophonicFMprogramscon-
necttothebackpaneljacksmarkedMONOOUT.The
programatthesejacksiscontrolledbythevolumecon-
trolonthefrontpanel.InthispositiontheSTEREOOUT
jackshavethesamemonophonicprogrambutwithout
thevolumecontrol.
2

Fig.5-MODESELECTORintheMPXSTEREOposition.
MPXSTEREO:
Inthispositiontheoutputofthemultiplexadapter
(thatcanbeinstalledonthechassisintheprepared
space)connectstothejacksmarkedSTEREOOUTon
thebackpanel.TheSTEREOOUTjacksarenotcontrolled
bythevolumecontrol.Therightchannelprogramisalso
connectedtothejacksmarkedMONOOUTandiscon-
trolledbythevolumecontrol.
Fig.6-MODESELECTORintheEXT.STEREOposition.
EXTSTEREO:
InthispositiontheMR-65isusedforstereobroad-
castsofFM-FMstereoorFM-AMstereo.Theswitchcon-
nectsthejackSTEREOIN-LEFTtothejackSTEREOOUT-
LEFTwithoutamplificationorvolumecontrol.TheSTEREO
OUT-RIGHTjackisconnectedtotheMR-65FMprogram
withoutthevolumecontrol.ForFM-FMstereoanother
FMtunercanbepluggedinthejackSTEREOIN-LEFT.
TheMR-65suppliestherightchannelprogramwhile
theexternaltunersuppliestheleftchannelprogram.
SimilarlyforFM-AMstereo,theAMtunercanbeplugged
intheSTEREOIN-LEFTjacktosupplyleftchannelpro-
gramwhiletheMR-65suppliestherightchannelprogram.
Againinthispositiontherightchannelprogramfrom
theMR-65isconnectedtotheMONOOUTjacksthrough
thevolumecontrol.
AUTO.FREQ.CONTROL
Fig.7-TheAUTOMATICFREQUENCYCONTROL
TheamountofAFCcanbevariedfromofftofullon
byturningthiscontrol.Turnedtotheextremeleftposi-
tiontheAFCisoff.Turnedtotheextremerightposition
AFCismaximum.
TheautomaticactionoftheAFCisanexclusive
Mclntoshdevelopment.TheAFCiselectronicallydelayed
toallowtuningwithoutAFC.Whentuningiscomplete,
AFCisautomaticallyrestored.
MUTING
Fig.8—TwopositionMUTINGswitch.
Betweenstationnoiseissuppressedwhiletuning
whenthisswitchisturnedtotheINposition.Ultra-sonic
muting,developedbyMclntosh,electronicallyturnsoff
thebetweenstationnoiseincludingthenoisesusually
heardwhentuninginandoutofa station.
BACKPANELFACILITIES
Fig.9—Rearofchassisshowingjacks,terminals,andadjustments.
MPXOUT
TheunfilteredoutputoftheMR-65isconnectedto
theMPXOUTjacktofeedanexternalmultiplexadapter.
TheFMprogramisalwaysconnectedtothisjackandis
notaffectedbythefrontpanelswitching.
MUTEADJ
Theultra-sonicmutingfeatureoftheMR-65isde-
signedtosuppressnoisebetweenstations.Thethres-
holdofthemutingisadjustedatthefactoryusingprecise
measuringinstruments.Wedonotrecommendcasual
adjustmentofthiscontrol.Intheeventitisnecessaryto
adjustthethreshold,turningtheMUTEADJcontrolto
therightlowersthethresholdofmutingandturningthe
controltotheleftraisesthethreshold.
MONOUT
Allmonophonicprogramsandallrightchannelstereo
programstunedinontheMR-65areconnectedtothe
MONOOUTjacks.Thesejacksareconnectedinparallel
andarefedfroma lowimpedancefeedbackamplifier.
Thefrontpanelvolumecontroladjuststheprogramlevel
fedtothese jacks.Theoutputlevelisvariableupto4
voltsdependingonvolumecontrolsetting.
STEREOIN
Thesejacksconnecta separatetunerthroughthe
frontpanelswitchingforFM-FMstereo.(Seethepara-
graphsPOWEROFFandEXTSTEREOunderMODE
SELECTORonpages2 and3 fora completeexplanation.)
STEREOOUT
Alowimpedancefeedbackamplifierwithoutvolume
controlfeedstheoutputjackmarkedRIGHT.TheLEFT
jackprogramconnectiondependsonthesettingofthe
MODESELECTOR(SeeMODESELECTORpage2.)The
outputvoltageoftheRIGHTjackisapproximately4 volts.
3

FMANT
Eithera 300ohmbalancedor75ohmunbalanced
antennacanbeconnectedtotheMR-65.The300ohm
inputisbalancedandconnectedinternallythrougha
specialbalundesignedbyMclntosh.The75ohmun-
balancedantennaconnectionisbetweenonesideof
the300ohminputandground.
TOTVSET
AVHFtelevisionantennamaybeusedforFMrecep-
tion.AninternalswitchontheMODESELECTORcon-
nectstheMR-65betweenaTVantennaandaTVreceiver.
WiththeMODESELECTORturnedtoanyoperatingposi-
tiontheVHF-TVantennaisdisconnectedfromtheTVset
andconnectedtotheMR-65.WhentheMR-65isturned
off,byrotatingtheMODESELECTORtothePOWEROFF
position,theantennaisswitcheddirectlytotheTV
receiver.
FUSE
TheMR-65usesa 1 ampere"SloBlo"typefuse.The
AuxiliaryACoutletisnotfused.
ACOUTLET
Amaximumof350wattsmaybeconnectedtothe
ACoutlet.Theoutletisnotfused.TheMODESELECTOR
onthefrontpanelcontrolsthepowertothisreceptacle
andturnsthepoweroffinthePOWEROFFposition.
LAMPS
Thediallightbrightnessiscontrolledbythisswitch.
SimplyswitchtoHIorLObrightnesstosuityourin-
stallation.
INSTALLATIONINSTRUCTIONS
TheMR-65canbeinstalledinconventionalcabinets,
custombuilt-insorprofessionalequipmentracks.Ifthe
MR-65istobeplacedona bookshelfortable-top,the
MclntoshModelL-66cabinetmaybeusedtoenclosethe
chassis.TheMR-65isinstalledfromthefrontofthe
cabinet.. . notfromtherear.Theminimumthicknessof
woodpanelsusedtomounttheMR-65shouldbe¼". . .
andpanelsupto1"thickmaybeused.
Ashelfisrequiredtosupporttherearofthechassis
whenthefrontpanelismadeofwood.Itisimportantto
makea suitablecutoutintheshelfforventilation.When
mountedona metalrackpanel,a shelfisnotneeded.
ThespaceinwhichtheMR-65willbeinstalledshould
beatleast13¾"behindthefrontpaneltoallowabout
1½"forconnectors.Allowatleast16½"forwidthand
5½"forheightsotherewillbesufficientspaceforcir-
culationofair.Theseareinsidedimensions.
Fig.10—Positions"A"to"C"showingthelocationof
theverticalcenterline;howthemeasuringtool
(mountingstrip)isusedtolocatethehorizontal
centertine,andtomeasureoffthetwopointsto
therightandleftoftheverticalcenterline.
MAKINGTHEFRONTPANELCUTOUT
Thepaneliscutoutusingthe"FRONTPANELCUT-
OUTTEMPLATE."Topositionthetemplateonthefront
ofthepanel,itisnecessarytomaketwolocatingholes
fromtheback(inside)ofthepanelusingoneofthe
mountingstrips(½"by3½")asa measuringtool.Pro-
ceedasfollows:
Measuretheexactcenteroftheproposedcutout
areaandscribea verticalcenterlinefromthetopofthe
paneldowntothetopsurfaceoftheshelf.Seeposition
"A"inFig.11.Drawa horizontalline3½"abovetheshelf
usingoneofthemountingstripsasa measuringtool.
Seeposition"B"inFig.11.Now—placea mountingstrip
alongthehorizontallinetotheleftoftheverticalcenter
lineandmarka point3½"leftfromtheverticalcenter
line.Repeatthisprocedureandmarka point3½"right
fromtheverticalcenterline.Thesepointsshouldnowbe
3½"upfromthetopoftheshelfand7"apart,one3½"to
theleftandone3½"totherightoftheverticalcenter
line.Seeposition"C"inFig.11.Drilla3/16"holeateach
point—takecaretoholdthedrillperpendiculartothefront
panelsothattheholewillbelocatedaccuratelyonthe
frontofthepanel.
Positionthetemplateonthefrontofthepanelusing
thetwolocatingholestolineitupcorrectly.Scribethe
rectangularopeningonthefrontpanelandmarkthe
positionofthesixmountingholes.Drillthesix3/16"
mountingholesbeforecuttingthepanelopening.Then
cutouttheopening.Itisimportantthatthecutoutbe
justwithinthelines.
MAKINGTHESHELFCUTOUTS
Iftheinstallationusesa shelf,itmustbecutoutto
provideventilationbelowthechassis.Tomakethecut-
out,usethe"SHELFCUTOUTTEMPLATE."Locatethe
centeroftheshelfandscribea linefromfronttoback.
Thetemplateismarkedforpanelthicknessesfrom¼"to
1".Foldonthelinethatcorrespondstothethicknessof
thepanel.Placeitontheshelfsothatitbuttsagainstthe
insideofthepanel.Matchthecenterlinemarkonthe
templatetothescribedcenterlineontheshelf.Markthe
positionofthefourholesandscribethesquareventila-
tionopening.Drillthefour¼"holesandcutoutthe
ventilationopening.
INSTALLINGTHEMR-65
RemovethefourscrewsholdingtheMR-65tothe
shippingpallet(savethesescrews,youwillneedthemif
yourcabinethasa ¼"or3/8"shelf.)Removethefour
plasticfeet.
Inthemountinghardwarepackagearefour6-32
flatheadscrewsandeight6-32roundheadscrews.Two
oftheflatheadscrewsoftheproperlengthareusedto
attachthemountingstripstothecabinet.Fourofthe
roundheadscrewsoftheproperlengthareusedto
attachtheMR-65tothecabinetandmountingstrips.
The6-32x ½"screwsaretobeusedwithpanelsunder
3/8"inthickness.The6-32x¼"screwsaretobeusedwith
panels½"to1"inthickness.
4

Fig.11—Securingthemountingstriptothefrontpanel.
Selecttheproperlength6-32flatheadscrewsand
usethemtoinstallthetwomountingstripsbehindthe
frontpanel.Besurethattheedgeofthestripwiththe
clipsistowardthepanelopening.Lineupthemounting
stripsoneachsideofthefrontpanelcutoutsothethree
holesinthestripareinlinewiththethreeholesinthe
panel;seeFig.11.Installtheproperlengthflathead
screwsinthecenterhole,anddrivetheminsotheflat-
headsareflushwiththepanel;ifnecessary,countersink
thetwocenterholes.
InserttheMR-65carefullyintothepanelopening
fromthefrontsothatitrestsontheshelf.Insertthe
properlength6-32roundheadscrewsintothefourholes
inthemountingflangesoneachendofthetunerfront
panelanddrivethemin,butdonottighten.
IFTHECABINETISFIXEDANDWILLNOTBEMOVED
ABOUT,ITISNOTNECESSARYTOSECURETHEMR-65
CHASSISTOTHESHELF.
Ifthisisthecase,tightenthefourscrewsholdingthe
frontpanel.Ifthecabinetistobemovedabout,itis
recommendedthattheMR-65chassisbesecuredtothe
shelf.Thefour10-32x ½"screwsusedinshippingare
suppliedforuseiftheshelfisunder3/8".Usethe10-32
x¾"screwsiftheshelfis½"or5/8"andthe10-32x 1"
screwsiftheshelfis¾"or7/8".Securethechassiswith
theproperlength10-32machinescrews,insertingthem
frombeneaththeshelf.Donottightenthe10-32screws
untilyouhavetightenedthefrontpanelscrews.Useof
thewronglength10-32screwsmaycauseelectrical
shortinginthecircuit.
Fig.12—Detailofhowthepanelendcapsarefittedto
theMR-65panel.
Attachthetwometalpanelendcaps(packedwith
mountinghardware)oneachendofthepanelbysliding
ontothepins.(SeeFig.3).Theendcapsareheldby
springtensionandcaneasilyberemovedifthechassis
istobetakenoutofthecabinet.
MOUNTINGINTHEL-66CABINET
TheMclntoshL-66cabinetissuppliedwithcomplete
instructionsandallnecessaryhardwareforinstallingthe
MR-65StereoFMTuner.ThedimensionsoftheL-66are
169/16"wideby611/16"high(includingmountingfeet)by
13¾"deep,includingthefrontpanelandcontrolknobs.
CONNECTINGTHEMR-65
MONOPHONICPROGRAMCONNECTIONS
MONOPHONICFMPROGRAM
Fig.13—Monophonicoutputwithvolumecontrol.
TheshieldedcablesuppliedwiththeMR-65isused
toconnecttheMR-65outputjackmarkedMON-OUTto
ahighlevel(tuneroraux.)inputofa preamplifieror
directlytoa poweramplifier(seeFig.13.)Theprogram
atMON-OUTjacksiscontrolledbythefrontpanelvolume
control.
Fig.14—Monophonicoutputwithoutvolumecontrol.
Ifyoudonotwishtousethevolumecontrolonthe
MR-65thenthecableispluggedinoneortheotherofthe
jacksmarkedSTEREO-OUT.(SeeFig.14).Theprogram
thenistakenfromtheMR-65aheadofthevolumecontrol.
STEREOPHONICPROGRAMCONNECTIONS
ForstereophonicprogramstheMR-65shouldbe
connectedtoa preamplifiercontrolcenter.TheMR-65
volumecontroldoesnotchangethetuneroutputpro-
gramlevelattheSTEREOOUTjacks.
5

STEREOWITHBUILT-INMPX
Fig.15—Stereooutputconnections.
Provisionshavebeenmadetoinstallanintegrated
multiplexadapteronthetopsurfaceoftheMR-65chas-
sis.AftertheF.C.C.haspublishedstandardsforstereo
multiplex,Mclntoshwillmanufacturesuchanadapter.
Afterthemultiplexadapterhasbeeninstalledonthe
MR-65chassis,connectionsforthestereoprogramare
madeattheSTEREO-OUTjacks.A shieldedcableis
pluggedintheSTEREO-OUT-LEFTjackandconnectedto
thelefttunerinputonthemusicsystem'spreamplifier.
Pluga secondshieldedcableintheSTEREO-OUT-RIGHT
jackoftheMR-65andconnectittotherighttunerinput
onthemusicsystem'spreamplifier.Programvolumeis
controlledatthemusicsystem'spreamplifier.The
volumecontrolontheMR-65doesnotoperateinthe
stereomodes.
ItisunnecessarytoconnecttheMONOFMoutput
jackstothepreamplifieriftheMR-65isconnectedfor
stereophonicoperation.ThemonophonicFMprogramis
internallyconnectedintheMR-65totheSTEREOOUT
jackswhentheMODESELECTORisintheFMposition.
STEREOWITHANEXTERNALMPXADAPTER
Fig.16—ConnectionsforanexternalMPXadapter.
Theunfiltered outputoftheMR-65isavailableatthe
jackmarkedMPXOUT.Plugtheinputoftheexternal
MPXadapterintothisjack.TheACpowercordforthe
adaptercanbepluggedintotheACreceptacleonthe
MR-65.TheMPXadapterwillthenbeturnedoffwhenthe
tuneristurnedoff.
FM-FMorFM-AMSTEREO
Fig.17—Connectionforexternaltunerforstereo.
TherightchannelprogramofFM-FMstereoorFM-AM
stereoistheMR-65program.Anexternaltunerisused
fortheleftchannelprogram.Theexternaltuneriscon-
nectedbya shieldedcabletotheSTEREOIN-LEFTjack.
Theleftchannelprogram(fromtheexternaltuner
throughtheMR-65switching)ispluggedintheSTEREO-
OUT-LEFTjackandconnectedtothelefttunerinputof
thepreamplifier.Therightchannelprogramsupplied
bytheMR-65ispluggedintheSTEREOOUT-RIGHT
jackandconnectedtotherighttunerinputofthepre-
amplifier.(SeeFig.17).TheMR-65volumecontroldoes
notoperateforthismethodofoperation.
ACPOWER
PlugtheACpowercordin105voltto125volt,50to
60cyclepowerline.ThepowerusedbytheMR-65is
75watts.
ANTENNACONNECTIONS
WiththeMR-65oneofthreeantennasystemscanbe
used:(1)theindoordipolesuppliedwiththeMR-65,
(2)anoutdoorFMantenna,or(3)a VHF-TVantenna.In
fringeareasbestresultswillprobablybeobtainedwith
theuseofanoutdoorFMantenna.Inmanyareasthe
indoordipoleantennaisusuallysatisfactory.Theuseof
aVHFTVantennaisalsoeffectiveinmanyinstallations.
Makea choiceafterconsultingyourdealer.
INDOORDIPOLEANTENNA
Fig.18—Connectionfor300ohmantenna.
Theflexiblefoldeddipoleantenna(300ohm)sup-
pliedwiththeMR-65isforindooruseinurbanorhigh
intensitysignalareas.Theflexibilityofthethinflatwire
assemblypermitsittobeplacedundera rug,tacked
behindthehi-fiequipmentenclosure...or,placedin
anyotherconvenientlocation.Insomecases,itmaybe
necessaryto"position"theantennaforbestsignal
reception.Thisshouldbedonebeforeitispermanently
locatedortackeddown.
TopositionthedipoleforbestresultstheMR-65
mustbeoperating.Thefollowingproceduremaybe
followed:Connectthetwoleadsfromthedipoletothe
terminalsmarkedFMANTontherearofthechassisof
theMR-65;seeFig.18.
IMPORTANT:BEFORETURNINGTHEMR-65ON,
CHECKTOSEETHATALLTUBESAREFIRMLYSEATED
INTHEIRSOCKETS,ANDTHATALLPLUGSARECOR-
RECTLYANDFIRMLYINSERTED.
TurnthepoweronbysettingtheMODESELECTOR
toFM.TurntheAFCControltoMIN,theMUTINGcontrol
toOUT.Openthedipoletoa full"T"andtunetheMR-65
toa fairlyweakstation.ObservetheSIGNALSTRENGTH
meteronthefrontpanelasyourotateandmovethedi-
poleabout.. . whenthemeterreadshighest,thedipole
isinthebestpositionformaximumsignalreceptionfor
thisstation.Thisisnota criticalposition;thereforeyou
maypermanentlyinstalltheantennaina positionwhich
mostcloselyconfirmstoit.
IMPORTANT:KEEPTHEDIPOLEAWAYFROM
METALSURFACES,METALDOORWAYS,ETC.,ASTHEY
USUALLYINTERFEREWITHITSEFFICIENCY.
OUTDOORANTENNA
Anoutdoorantennaisrecommendedforoptimum
performanceinallareas.Infringe(outlying)areas,best
resultswillbeobtainedwitha highlydirectionalFM
antennausedinconjunctionwitha rotator.Inthisin-
stance,theSIGNALSTRENGTHmetermaybeusedasan
indicatoroftheantenna'sdirectionandpositionfor
maximumsignal.Connectthe300ohmantennatothe
terminalscrewsmarkedFMANTasinFig.18.
6

CONNECTINGA 75OHMCOAXIALANTENNALEADVHF-TVANTENNACONNECTION
Fig.19—Connectionsfora 75ohmantenna.
Anunbalanced75ohmantennacanbeconnected
totheMR-65withcoaxialcable.Connectthecentercon-
ductortotherightFMANTscrewandtheshieldtothe
groundingscrewnexttotheantennascrewasinFig.19.
TheMclntoshdesignedbalunmatchesthe75ohminput
tothetunerforoptimumperformance.
Fig.20-Connectionsforsharinga VHF-TVantenna.
TheMODESELECTORswitchdisconnectstheVHF-
TVantennafromtheTVsetandconnectsittotheMR-65.
WhentheMR-65isturnedofftheswitchre-connectsthe
antennatotheTVset.
ConnecttheVHF-TVantennatotheFMANTtermi-
nalsandconnecta 300ohmflatribbonwirefromthe
terminalsmarkedTOTVSETtotheantennaterminals
ontheTVset.(SeeFig.20).
OPERATINGTHEMR-65
Fig.21-FrontPanelControls.
MONOPH0NICFMPROGRAM
TurningtheMODESELECTORtoFMturnstheMR-65
poweron.TurntheVOLUMECONTROLtoitsmidpoint,
theAUTO.FREQ.CONTROLallthewaytotheright,and
theMUTINGswitchtotheINposition.Aftera warmup
ofabout30secondsturnthetuningknobtofindthe
stationofyourchoice.
WhiletuningtheMR-65youmaynoticethemeters
indicatinga stationyetnoprogramisheardfromthe
speakers.Themutingcircuitinthetunerisrejectingthe
stationbecausethereisobjectionablenoisewiththe
weaksignalfromthestation.TurntheMUTINGswitchto
theOUTpositionandthestationwillbeheard.Most
programsthatcanbetunedinthismannerareofpoor
qualityduetointerferingnoise.
TheAFCactioniselectricallydelayedtopermittuning
withoutAFCandwithoutturningswitchestodisablethe
AFC.AftertuningiscompletetheAFCautomaticallylocks
onthestation.TheMR-65maybeaccuratelytunedwith-
outhavingto"splithairs."Theverybestperformance
witha minimumofexperienceoreffortresultsfromthe
actionofthenewAFCcircuit.Forcriticaltuning,merely
tuneuntila stationisheardfromthespeaker,andthen
theAFC,aftera fewsecondsdelay,automaticallycenters
thestationonthechannel.
IftwostationsarenexttoeachothertheAFCaction
maytendtocaptureandholdthestrongerstation.By
turningtheAFCknobtothelefttheamountofAFCis
reducedandtheweakerstationofthetwocanbetuned
andheld.Thequalityoftheaudioprogramisunaffected
bytheamountofAFCused.
STEREOPHONIC-INTERNALMULTIPLEX(MPX)
AftertheMPXadapterhasbeeninstalledinthe
preparedspaceonthechassis,MPXstereobroadcast
programscanbereceived.TurntheMODESELECTOR
toMPXSTEREOandusetherestofthecontrolsasin
"MonophonicFMProgram"above.Thevolumecontrol
isnotoperatinginthisposition.
WhentheMR-65istunedtoanystationbroadcasting
stereotheMPXadapterwillseparatethe"left"and
"right"channelsforstereoreproductionbytheloud-
speakers.
STEREOPHONIC-EXTERNALMULTIPLEX(MPX)
Withanexternalmultiplexadapterpluggedinthe
MPXOUTjackallcontrolsaresetidenticallytothe
"MonophonicFM"settings.
STEREOPHONIC-FM-FMorFM-AM
Witha separatetunerpluggedintheSTEREOIN-
LEFTjacksandtheMODESELECTORintheEXTSTEREO
positionFM-FMorFM-AMstereobroadcastcanbetuned.
TheMR-65suppliestherightchannelprogramandthe
separatetunersuppliestheleftchannelprogram.
7

ADJUSTMENTS
Fig.22—TUNINGmeteradjustment.
TUNINGMETER
ThemeteradjustmentsaremadewiththeMR-65
turnedon.TurntheMODESELECTORtotheFMposition,
theMUTINGswitchtotheOUTposition,theAUTO.
FREQ.CONTROLtotheextremeleft,andtheVOLUME
toa comfortableloudness.Turnthetuningknobsothat
thedialpointerisnearthecenterofthedialscalebut
notonorneara station.Theredknobundertheright
panelendcapcentersthepointerintheTUNINGmeter.
Turntheredknobuntilthepointerisinthecenterofthe
blackareaontheTUNINGmeterface.
Fig.23—SIGNALSTRENGTHmeteradjustment.
SIGNALSTRENGTHMETER
TheSIGNALSTRENGTHadjustmentistheredknob
undertheleftpanelendcap.WiththeMR-65stilltuned
asaboveadjustthisredknobuntilthepointermoves
overthezero(0)ontheSIGNALSTRENGTHmeterface.
Bothmetersarenowproperlyadjusted.
DIALLIGHTS
Adjustmentofthedialscalelightingcanbemadeon
therearofthechassis.SettheswitchmarkedLAMPS
forHIifyouwantmorelight,andLOifyouwanta dimmer
lightplusextendedlamplife.
GUARANTEE
MclntoshLaboratoryIncorporatedguaranteesthe
mechanicalandelectricalworkmanshipandcompon-
entsofthisequipmenttobefreeofdefectsfora
periodof90daysfromdateofpurchase.Wefurther
guaranteethisequipmenttoperformasadvertised.
Thisguaranteedoesnotextendtocomponentsdam-
agedbyimproperusenordoesitextendtotransporta-
tiontoandfromthefactory.
3-YEARFACTORYSERVICECONTRACT
Anapplicationfora FREE3-YEARFACTORYSERVICECONTRACT
isincludedinthepocketonthebackcoverofthismanual.
8Designsubjecttochangewithoutnotice.
TheMR-65youhavepurchasedwiltgiveyouyearsofpleasant
andsatisfactoryperformance.Ifyouhaveanyquestionsconcerning
theoperationormaintenanceofthistunerpleasecontact:
CustomerService
MclntoshLaboratoryInc.
2ChambersStreet
Binghamton,NewYork
Ourtelephonenumberis723-5491.
Thedirectdialareacodeis607.

LABORATORY ,INC .
2CHAMBERSSTREET,BINGHAMTON,N.Y.
MadeinU.S.A.
Phone-AreaCode607-723-5491
650M-2M-HP
PrintedinU.S.A.