McIntosh MI-3 User manual

MAXIMUM PERFORMANCE INDICATOR
MI3

GENERAL
DESCRIPTION
THANKYOUfor
purchasingthisMl3.To
insureyourenjoyment
pleasereadthismanual
carefullyandfollow
instructions.
CONTENTS
GENERALDESCRIPTION1
TECHNICALDESCRIPTION2
SPECIFICATIONS3
FRONTPANELINFORMATION4
BACKPANELINFORMATION5
CABINETINSTALLATIONS6
CONNECTIONS7,8
SETUPPROCEDURES9
SYSTEMHOOKUP10
TYPICALPATTERNS11
GUARANTEE12
TheMclntoshMl3 isfivelaboratoryinstrumentscombinedintoone
compactinstrument.Itisa professionaloscilloscope,relativesignal
strengthindicator,calibratedFMdeviationmeter,calibratedbalance
meter,andphaseindicator.TheseinstrumentsareusedbyFMstations
todeterminethebestpossibleperformanceforyourlisteningenjoyment.
TheMclntoshMl3 MaximumPerformanceIndicatormakesiteasyfor
youtoattainprofessionalbroadcastingqualityFMlistening.
TheMclntoshMl3 showsyouwhatyouneedtodotoimproveyour
system'soverallperformance.ItisdesignedtobeusedwithanFM
tunerandstereopreamplifier.
WhentheMl3 isusedwithanFMtuneritwilldetectanddisplay
multipathreception.Multipathreceptionistheresultofa reflected
signalarrivingatthetunerantennaslightlylaterthanthedirectsignal.
ByrotatingorrepositioningyourFMantennaitispossibletoreduce
themultipathreception.TheMl3 MaximumPerformanceIndicator
makesiteasytoknowwhentheFMantennaisorientedforthebest
receptionofanystation.
ToshowmultipathreceptiontheMl3 displaysinstantaneoussignal
strengthversusfrequencydeviation.Signalstrengthisshownasvertical
deflectionoftheindicatordisplaybeam.Frequency deviation isshown
ashorizontaldeflection.Multipathreceptionappearsasa peakor
valleyintheMl3 picturetubedisplay.
MultipathreceptiondegradesFMtunerperformanceinseveralways:
1.Usuallythereisanincreaseinbackgroundnoiselevel.
2.Distortionisoftenheardintheprogramsignal.
3.Stereoseparationmaybereduced.
4.Thestereoeffectmaybecompletelylost.
5.Stereoindicatorsmayfailtofunction,orfunctionerratically.
Toovercomemultipathreceptionitisusuallynecessarytoturnthe
antennatoreceivetheFMsignalbyonepredominantpath.Rotatinga
directionalantennaiseffectiveatcorrectingmultipathreception.Ina
metropolitanareawhere a simpleantenna such asa dipole is used
repositioning the antenna will achieve the same result.
TheMl3 isa veryeffectivetuningindicator:
1.Signalstrengthisshownbytheverticalpositionofthedisplay
trace.Thehigherthepositionofthetracethegreaterthesignal
strength.
MAXIMUM PERFORMANCE INDICATOR
MI3
1

2.Correcttuningoccurswhenthedisplaytraceiscenteredhori-
zontallyonthescreen.Sincethedisplaytraceeffectivelyfollows
thetunerI.F.responsecurve,centeringthetracetunesthede-
tectortothecenteroftheI.F.curve.
TheMl3 MaximumPerformanceIndicatorisa versatileinstrument.
Whenusedwitheithera stereopreamplifier,or poweramplifierthe
Ml3 whenswitchedtotheL+RAUDIOpositionwillshowyouthe
characteroftheaudiosignalspresent.TheMl3 will:
1.Displaya tracealongtheL+Rlinewhena monauralprogram
isplaying.
2.WilldisplayalongtheL —Rlinewhena monauralprogram
sourcehasonechanneloutofphase.
3.Displaya verticaltraceifonlytheleftchannelisbeingde-
livered.
4.Displaya horizontaltracewhenonlytherightchannelisbeing
delivered.
5.Helpsyousettheprecisebalanceofyoursystem.Withthebal-
ancecontrolyoucanchangetheangleoftheL+RorL—Rdisplay.
6.A stereoprogramwillbea complexandvaryingcircularor
ellipticaldisplayofirregularoutlinethatdependsonchannel
separationoronthephaseamplituderelationoftheleftand
rightchannel.
TECHNICAL
DESCRIPTION
TheMl3 MaximumPerformanceIndicatorisessentiallyanoscilloscope
usinga threeinchcathode-raytube.Adequatebrightnessisassured
witha 1350voltacceleratingvoltage.A sharperwelldefinedtraceis
providedbyusingseparatefocusandastigmatismcontrols.
Twoidenticaldirectcoupledpush-pullamplifiersareusedinthehori-
zontalandverticaldeflectioncircuits.PhaseshiftineachamplifierIs
heldtowithina fewdegreesfromD.C.throughouttheoperating
frequencyrange.Phasedifferencesbetweenverticalandhorizontal
amplifiersareheldtowithina fewdegrees.
Thehighvoltagepowersupplyusesa seleniumrectifier.Thelowvolt-
agesuppliesuseseleniumrectifiers,twogasfilledrectangulartubes
andanelectronicvoltageregulator.Theoperatingvoltagesfrom
thesesuppliesarecarefullyregulatedovera widerangeofpower
linevariations.Thisdesignfeatureassuresa steadyindicatortrace
despitechanginglinevoltage.
Formultipathdisplaythehorizontaldeflectionvoltageisobtained
fromthetunerdiscriminatoroutputaheadofthede-emphasisnetwork.
ThisvoltageisproportionaltothefrequencydeviationoftheFM
transmission.Themaximumwidthoftheindicatorscreenisdesignedto
correspondtoapproximatelyplusandminus75kilocycledeviationof
theFMtransmitter.
Thehorizontalmultipathinputisconnectedthroughthedeviationinput
jackandthedeviation(horizontal)calibrationcontrol.
Formultipathdisplaytheverticaldeflectionvoltageisobtainedfrom
thetunerAutomaticGainControlcircuitattheinputtothefirstlimiter.
ThisvoltageisproportionaltotheFMstationsinstantaneoussignal
strength.However,theaverageproportionallyisexpotential.Because
oftheexpotentialcharacteristic,a weakstationwillproduceadequate
verticaldeflection.A powerfullocalstationshouldpositionthecenter
oftheindicatortraceabouthalftothreequartersofaninchbelowthe
topoftheverticalscale.TheverticalMultipathInputisconnected
throughtheSignalStrengthInputandtheSignalStrength(vertical)
CalibrationInputControl.
ForL+Raudiodisplaythehorizontaldeflectionvoltageisobtained
fromtherightchanneloutputofa tuner,a preamplifierorevena
poweramplifier.Thedeflectionvoltageisconnectedthroughthe
RightAudioInputandtheRightGainControl.ForL+ R audiodisplay
theverticaldeflectionvoltageisobtainedfromtheleftchanneloutput
ofa tuner,a preamplifier,ora poweramplifier.Thedeflectionvoltage
isconnectedthroughtheLeftAudioInputandtheLeftGainControl.
Witha normalloudnessmonauralsignalbothaudioinputcontrolsare
adjustedforequaldeflectionofthedisplaytrace.(Atthispointthe
tracewillbeontheL+R lineifthetwosignalsareinphaseorthe
L- R lineiftheyare1 80°outofphase.)

MI3SPECIFICATIONS
SENSITIVITY
SignalStrength(vertical)Input—700MV
LeftAudio(vertical)Input20MV
Deviation(horizontal)Input±350MV
RightAudio(horizontal)Input20MV
DIMENSIONS
Frontpanel:16incheswideby5-7/16inches
high; chassis (includingPANLOC shelf) 15
incheswideby5 incheshighby13inches
deep,includingconnectors;clearancein
frontofmountingpanelincludingknobs,
1½inches.
TUBEANDSEMICONDUCTOR
COMPLEMENT
1—3RP1,3 inchcathoderaytube.
4—6EA8,horizontalandverticaldeflection
amplifiers.
1—6EA8,electronicvoltageregulator.
2—OB2,voltageregulators.
1—Seleniumrectifier,highvoltagerectifier.
6—Seleniumrectifiers,low-voltagesupply.
4—siliconplanartransistors.
WEIGHT
Chassisonly,23pounds.
Inshippingcarton,30pounds.
FINISH
Anodizedgoldandblackglassfrontpanel
POWERCONSUMPTION
50watts,105to125volts.
50to60cycles.
FUSE
1AmpereSlo-Blo
3

FRONT
PANEL
INFORMATION
INDICATORSCREEN—Thescreenisthefaceofa cathode
raytube.Calibrationmarksareprovidedtoallowcorrect
positioningoftheindicatortrace.
Acorrectlytunedstationfreeofmultipathdistortionappears
asa smoothcurvecenteredontheindicatorscreenvertical
scale.Theverticallineismarkedtoshowtherelativestrength
oftheFMsignal.A stronglocalsignalshouldpositionthedis-
playabout½ to¾ inchfromthetopoftheverticalscale.
Thehorizontallineismarkedtoshowdeviation.
Thetwo45°slopedlinesshowL+RandL—Raudioinformation.
SCOPETEST—Thiscontrolswitchestheindicatorcircuitsto
show multipath, Left and Right audio signals or TEST. The
TESTpositionswitchestheindicatortracetoa singledotfor
adjustmentoftraceposition,focusandintensity.Different
tracereferencepositionsarenecessaryformultipathand
L+R Audio.
HORIZONTALPOSITION—Thiscontrol moves the indi-
catortracetotheleftorright.WiththeScopeTestswitchin
TEST position, the trace dottan easily be centered onthe
indicatorscreen.
VERTICALPOSITION—Thiscontrolmovestheindicator
trace upor down. With the Scope Test switch in TEST posi-
tiontheindicatortracecanbeeasilymovedtothecorrect
verticalposition.Formultipathdisplaythetraceispositioned
atthebottomreferencepoint.
Foraudioindicationsthetraceispositionedatthecenter
reference point. This shift in position occurs automatically as
theScopeTestcontrolisturned.Aninternaladjustment
labeledL+Rpositionisfactorypresetbutcanbereadjusted
ifneeded.
INTENSITY—Thiscontroladjuststhebrightnessoftheindi-
catortrace.AftertheIntensitycontrolhasbeentuned,the
Focuscontrolmayhavetobeadjustedforthebestpossible
indicatortrace.
FOCUS—Thiscontroladjuststhesharpnessandclarityof
theindicatortrace.FocusiseasiestwiththeScopeTest
switchintheTESTposition.
AUDIODISPLAY—Thiscontrolwillincreasethedisplay
areaonthefaceofthecathoderaytube.Atlowvolumes
youwillFindthedisplaywouldbesmall.Toseeallthein-
formationpresentturntheAUDIODISPLAYtowardmax.
Thiswillincreasethesizeofthedisplay.Athighvolumesyou
maywanttoturndowntheAUDIODISPLAYtoreducethe
sizeofthedisplay.
4

SIGNALSTRENGTH(VERTICAL)
MULTIPATHCONTROL
ThiscontroladjuststhepositionoftheMultipath
tracedisplayalongtheverticalscaleoftheindi-
catorscreen.
DEVIATION(HORIZONTAL)
MULTIPATHCONTROL
Thiscontroladjuststhemaximumwidthofthe
multipathtracedisplayalongthehorizontalscale
oftheindicatorscreen.
LEFT GAIN (VERTICAL)
AUDIOCONTROL
Thiscontroladjuststhemaximumverticalindicator
tracedeflectionfora leftchannelaudiosignal.
RIGHTGAIN(HORIZONTAL)
AUDIOCONTROL
Thiscontroladjuststhemaximumhorizontalindi-
catortracedeflectionfroma rightchannelaudio
signal.
SIGNALSTRENGTHINPUT(TP1)
Thisinputconnectstoa MclntoshtunerTestPoint
No.1,whichsuppliesa voltageproportionalto
SignalStrengthforverticaldeflectionoftheindi-
catortrace.
DEVIATIONINPUT(TP2)
Thisinputconnectstoa MclntoshtunerTest
PointNo.2,whichsuppliesa voltagepro-
portionaltodeviationoftheFMtrans-
missionforhorizontaldeflectionofthe
indicatortrace.
LEFTAUDIOINPUT
Thisinputconnectstotheleftoutputofa
tuner,preamplifier,orpoweramplifier.
Theleftchannelaudiosignalvoltage
causesverticaldeflectionoftheindicator
trace.Thisinputjackisinparallelwiththe
leftaudiooutputjack.
LEFTAUDIOOUTPUT
Thisoutputjackisinparallelwiththeleft
audioinputjack.Thisparallelconnection
makesitconvenientforconnectinga pre-
amplifierortuneroutputtoboththeMl3
andthepoweramplifier.
RIGHTAUDIOINPUT
Thisinputconnectstotherightoutputofa
tuner,preamplifier,orpoweramplifier.
Therightchannelaudiosignalvoltage
causesahorizontaldeflectionoftheindica-
tortrace.Thisinputjackisinparallelwith
therightaudiooutputjacks.
RIGHTAUDIOOUTPUT
Thisoutputjackisinparallelwiththeright
audioinputjack.Thisparallelconnection
makesitconvenientforconnectinga pre-
amplifierortuneroutputtoboththeMl3
andthepoweramplifier.
1ASLOBLO
A1 ampereSLO-BLOfuseprotectsthe
Ml3 indicatorcircuits.Thisfusedoesnot
protectadditionalequipmentconnectedto
thebackpanelACoutlets.
350WATTSACOUTLET
A117voltACoutletisprovidedforextra
equipmentdrawingasmuchas350watts
power.Theoutletisnotfusedandison
whenevertheMl3 powercordisconnected
toanACoutlet.
5
BACK
PANEL
INFORMATION

HOWTOINSTALLYOUR
Ml3 INA CABINET
1Usethemountingtemplatetopositionwhereyouwillmountthe
instrument.
NOTE:Thetemplateletsyoupositionthecutoutfromthefrontof
thepanel.
2Markthe"A"and"B"drillholes.
3Markthefourcorners.Jointhefourcornerstomakea rectangle.
Usetheedgeofthetemplateasa straightedge.
4Drillthemountingholesandcutouttherectangularhole.
5Fastenthetwomountingstripstothepanel.Usetwoofthefillister-
headscrewsprovided.Thereare12fillister-headscrewsinthe
package.Sixare% incheslongandsixare1 % incheslong.For
panelsunder½ inchthickusethe¾ inchscrews.Forpanelsover
½inchthickusethe1¼inchscrews.Inserta screwinthecenter
hole.("B"holeonthetemplate.)Tightenthescrewssotheheads
arepulledhalfoftheirthicknessintothewood.
6Fastentheshelvestothemountingbrackets.Usetwofillister-head
screwsinthe"A"holesforeachshelf.
7Placethetemplateoverthemountingscrews.Thescrewsshould
becenteredinthe"A"and"B"holesonthetemplate.ThePAN-
LOCshelvesshouldmatchtheverticaldashlinesonthetemplate.
8Removetheplasticprotectivecoveringfromtheinstrument.Turn
theinstrumentover.Topreventdamageresttheinstrumenton
theshippingpallet.
9Removethefour(4)plasticfeet.
10Nowtheinstrumentisreadyforinstallation.
11Putthepowercordthroughtheopening.Slidetheunitintothe
brackets.CarefullyslidetheMl3 intotheopeningsotheplastic
railsonthebottomofthechassisengagethegroovesinthemetal
mountingbrackets.SlidetheMl3 inuntilitsfrontpanelisagainst
thecabinetmountingpanel.
12Securetheinstrumenttothemountingbracketbypushing"in"the
PanlocButtons.
6

TWOPAIRSOF3 FOOTLONGLOWLOSSSHIELDEDCABLESARE
SUPPLIEDWITHTHEMl3.USETHESECABLESTOCONNECTTHE
Ml3 TOA TUNERFORMULTIPATHRECEPTION.A PAIROF6
FOOTLONGSHIELDEDCABLESARESUPPLIEDFORCONNECTING
THEMl3 INAUDIOCIRCUITS.
CONNECTINGTOMclNTOSHMR71ORMR67TUNER.
Connecta 3 footlowlossshieldedcablefromtheTPNo.1 (TestPoint
No.1 jackontopofthetunerchassis)totheSignalStrength(vertical)
InputontheMl3.
Connecta second3 footlowlossshieldedcablefromtheTPNo.2
(TestPointNo.2 jackonrearofthetunerchassis)tothedeviation
(horizontal)InputontheMl3.
cabletothetunerchassisground.Useoneofthe1 footlonglow-loss
shieldedcables,strippedandtinnedononeend(femalejacksonthe
otherend)suppliedwiththeMl3.
Usea connectorwithmaleplugstoconnectthesoldered-incablefrom
thetunertotheDeviation(horizontal)InputontheMl3.Connecta 3 foot
low-lossshieldedcablefromthetestpoint(ontopoftunerchassis)tothe
SignalStrength(vertical)InputontheMl3.
CONNECTINGTOMclNTOSHMR65BTUNER.
RemovecapacitorC 27(.005MFD)connectedbetweenTPNo.1 and
chassisground.MR65Btuners,serialnumbers300UOandabove,donot
havethiscapacitor.
Connecta 3 footlow-lossshieldedcablefromtheMR65BTPNo.1 (Test
PointNo.1 ontunerbackpanel)totheSignalStrength(vertical)Input
ontheMl3.
Connecta 3 footlonglow-lossshieldedcablefromtheMR65BTPNo.2
(TestPointNo.2 onrearoftunerchassis)totheDeviation(horizontal)
InputontheMl3.
CONNECTINGTOMclNTOSHMX110TUNER-PREAMPLIFIER
WITHZ ORX SERIALNUMBERS
Connecta 3 footlowlossshieldedcablefromtheMX1 1 0 TPNo.1
(TestPointNo.1 jackontopofthetunerchassis)totheSignalStrength
(vertical)InputontheMl3.
Connecta second3 footlow-lossshieldedcablefromtheMX110TP
No.2 (TestPointNo.2 jackontopofthetunerchassis)totheDeviation
(horizontal)InputontheMl3.
CONNECTINGTOMclNTOSHMX110TUNER-PREAMPLIFIER
WITHM SERIALNUMBERS
RemovecapacitorC 1 30(.005MF)connectedbetweenthetestpoint
andground.
Solderthecenterleadofa 1 footlow-lossshieldedcabletothejunction
pointofR 139(10K)andC 125(.1MFD).Soldertheoutershieldofthe
CONNECTINGTOMclNTOSHMR65AND65A
RemovecapacitorC 31(.005MFD)connectedbetweenthetestpoint
andground.
Connecta 3 footlow-lossshieldedcablefromtheMR65ATestPoint
(jackontopoftunerchassis)totheSignalStrength(vertical)Inputon
theMl3.
Connecta 3 footlow-lossshieldedcablefromtheMR65AMPXoutjack
onthetunerbackpaneltotheDeviation(horizontal)InputontheMl3.
IfanexternalmultiplexadapterisbeingusedwiththeMR65a "Y"
connectorwillbeneededintheMPXoutputjack.Thisallowsboththe
MPXadapterandtheleadtotheMl3 tobeconnected.
CONNECTINGTOMclNTOSHMR66TUNER
RemovecapacitorC 1 25(.005MFD)connectedbetweenthetestpoint
andground.
7

Connecta 3 footlow-lossshieldedcablefromtheTESTPOINT(ontop
oftunerchassis)totheSignalStrength(vertical)InputontheMl3.
Connecta 3 footlow-lossshieldedcablefromtheFMmultiplexoutput
jackonthetunerbackpaneltotheDeviation(horizontal)Inputonthe
Ml3.
CONNECTINGTOMclNTOSHMR55ATUNER
Removethefeed-throughcapacitorL 43(1000MMF)connectedto
TPNo.1.Thiscapacitorcanbestberemovedbyunsoldering.Solderthe
centerleadofa 1 footlow-lossshieldedcabletotheTestPointendof
R27(100Kresistor).Soldertheoutershieldofthecabletothechassis
wherethefeedthroughcapacitorwassoldered.Thecablecanfeed
throughtheholeInthechassiswherethecapacitorwassoldered.Useone
ofthe1 footlonglow-lossshieldedcables,strippedandtinnedonone
end(femalejacksontheotherend)suppliedwiththeMi3.
Usea connectorwithmaleplugstoconnectthesoldered-incabletothe
signalstrength(vertical)InputontheMl3.Connecta 3 footlow-loss
shieldedcablefromthemulti-out(multiplexoutput)jackonthetunerto
theDeviation(horizontal)Input.
Ifa multiplexadapterisbeingusedwiththeMR55A,a "Y"connector
willbeneededintheMULTI-OUTjack.Thisallowsboththemultiplex
adapterandtheleadtotheMl3 tobeconnected.
CONNECTINGTOMclNTOSHMR55TUNER
Soldera wireacrossresistorR 62
thetunerchassis.
meg)connectedtothetestpointon
Connecta 3 footlow-lossshieldedcablefromthetestpointontopofthe
tunerchassistotheSignalStrength(vertical)InputontheMl3.
Connecta 3 footlow-lossshieldedcablefromtheMULTIPLEXOUTPUT
jackonthetunertotheDeviation(horizontal)InputontheMl3.
Connecta low-lossshieldedcablefromthediscriminatoroutput(ahead
ofthede-emphasisnetwork)totheDeviation(horizontal)Inputonthe
Ml3.
AdjusttheSIGNALSTRENGTH(vertical)Multipathcontrolontheback
paneluntilthepatternontheindicatorscreenisabout¾ inchfromthe
topoftheverticalscale.
DEVIATIONMULTIPATHCONTROL
Tuneina relativelystronglocalsignalwiththeantennapositionedfor
maximummultipath.
AdjusttheDEVIATION(horizontal)Multipathcontroluntilthehorizontal
pattern(loudestsignalfromthestation)doesnotextendovertheendsof
thehorizontalscaleoftheindicatorscreen.
L+RAUDIOINDICATIONS
TurntheMl3 PowerswitchtoON.
TurntheSCOPETESTswitchtoTEST.
AdjusttheHORIZONTALPOSITIONfrontpanelcontroluntilthetraceis
centeredhorizontallyontheIndicatorscreen.Calibrationlinesarepro-
videdontheIndicatorfaceforcenteringpurposes.
Adjusttheverticalpositioncontroluntilthetracedotispositionedatthe
bottomofthecenterverticalscale.
AdjusttheINTENSITYANDFOCUScontrolsfora sharpandcleartrace
dot.
TurntheSCOPETESTswitchtoL + R Audio.
SetthepreamplifierorpoweramplifiertoMONO.
Adjust the LEFT GAIN and RIGHT GAIN controls ontheMl3 until the
incomingprogramcausestheIndicatortracetoaligndirectlyoverthe
line.
CONNECTINGTOALLOTHERTUNERS
Connecta low-lossshieldedcablefromtheinputtothefirstFMlimiter
througha 100Kresistor,totheSignalStrength(vertical)InputontheMl3.NOWYOURMl3 ISREADYTOHELPYOUACHIEVEMAXIMUM
PERFORMANCEFROMYOURSYSTEM
8