Olympus OM-4 User manual

C&CASSOCIATES
troubleshooting
ELECTRONICTROUBLESHOOTINGTHEOLYMPUSOM-4
1.CIRCUITDESCRIPTION
PowerCircuit
AswithotherOM-seriescameras,batterypositive
connectstothechassisandtotheflexcircuitthrough
screwsholdingthecircuitinplace.Inthisguide,battery
positiveisdesignatedasVccandconnectionstothe
chassisareshownasthe"earth"symbol,
AblackwireconnectsbatterynegativetotheShutter
TerminalBoardandtothemainflexneartherowsof
variableresistors,Fromthere,conductorsfanouttopins
22,51,IC-101;pins6,26,62,IC-102;andpin13,IC-103.
TheDisplayFlexandResetBoardreceivebattery
negativethrougha blackwiresolderedtotheMainFlex
nearIC-101,
Whenbatteriesareinstalled,a quartzoscillator
involvingtwocapacitorsandIC-101isactivated.
Pressingthereleasebuttonone-halfstrokeclosesswitch
SW-I11toconnectpins15and18,IC-101.IC-101then
signalsIC-102topowerupthemeteringcircuitandthe
LCDforabout2 minutes.Powersignalsarefrompins53,
54,IC-101topins24,23,IC-102.Pressingtherelease
buttonrenewsthe2-minutepowerlatch,A 1.8vconstant
voltage,Vrefsisgeneratedatpin75,IC-102.
Adiodeisconnectedtothebatteryterminalsinreverse
directiontoprotectthecircuitifbatteriesareinstalled
backward.
Batteryrequirement:twoS-76silveroxideortwo
LR44alkaline-manganese.
MeteringCircuit
TherearefourICsinvolvedinmetering,exposure
control,anddisplay.IC-101containsa microprocessor
(CPU)andunderstandsonlybinarysignalsasinputsand
outputs.Itkeepstrackofmode,calculatesexposures,
andownstheclock.IC-102isa bipolarICwhichcontains
comparatorsforA/Dconversion,watchesovervariable
resistors,controlsmagnetsandLEDs,and
communicateswithIC-101,
IC-103,underthefloorpanelofthemirrorbox,
supports"average"and"spot"photodiodeswith
amplifiersandtemperaturecompensationcircuits.Italso
takescareofintegrationforautomaticexposurein
ambientandflashmodes.IC-104isa decoder/driverfor
thecomprehensiveLCD.
Priortoexposurea sub-mirrorbehindthereflex
mirrorreflectsa portionoflightgoingtotheviewfinder
tothephotodiodesonIC-103,A BVvoltage,changing
18mv/Evwithlight,isoutputfrompin16,IC-103topin
7,IC-102,Atthesametime,IC-102watchesaperture
setting(AV-VRatpin74),ASA(SV-VRatpin67),and
shutterspeedsetting(TV-VRatpin73).Although
variableresistorsareusedstheyarepartofananalog-to-
digitalconversionprocesswhichchangesallexposure
informationtobinarycodesfortheCPU.
Thecodeissentbackasseriesdatafrompin38,IC-102
topin29,IC-101sotheCPUknowsASA,aperture
setting,andshutterspeedsetting.HowtheCPU
interpretsthedatadependsuponoperatingmode
selected,IC-101willcalculateanexposure,thensenda
codedmessagetoIC-104whichdrivesanLCDdisplayto
indicateexposureandotherinformation,A quartzclock
operatingat32.8KHzkeepstheoperationorderlyand
thewholeprocessisrepeatedevery100mstokeepdataup
todate,
IC-101sendsdigital-to-analogdataalongeightlines
(DAC-0toDAC-7).DuringexposureinManualand
Spotmodes,IC-103willneedanalogvoltagetoset
exposuretimes.
Detailssuchasdifferentvoltagelevelsbetweenaverage
andspotSPDsaretakencareofbyvoltageboosting
circuits.Becauseofa wideexposurerange,integration
capacitorsareswitchedinandoutofcircuitaccordingto
ASAsetting,
ReleaseCircuit
Pressingthereleasebuttonfullstrokemechanically
unlatchesthemirroraswithotherOM-seriescameras,As
themirrorrises,switchSW-101closestoconnectVcc
(B+)throughtwodiodestobasesoftransistorsQ-103and
Q-904.Asthetransistorsturnon,pin49,IC-101issetlow
andpin58,IC-102issethigh.InthismannertheICsare
toldthemirrorisonitswayupandtheyhadbettergel
readyforanexposure.IC-101storesexposuredataand
LEDsaretemporarilydisabledtoconservepower.
IC-101alsosetsanexposureprogramaccordingtomode.
IC-102testsbatteryvoltagetobesureitisabove2.65v,
thenpin61goeslow.Pin61isconnectedtothebaseof
transistorQ-201(PNP)ontheshutterboard,Q-201
switchesoncausingcapacitorC-201todischargethrough
thecoilofcombinationmagnetM-l.M-lrepelsits
keeperwhichunlatchestheopeningcurtain,IC-102then
waitsforswitchSW-103,theTriggerSwitch(Timing
Switch),tosignalthefirstcurtainismovingbefore
initiatingexposurecontrol.

Ifbatteryvoltage isbelow2.65vorthereareno
batteries,IC-102doesnotreleasetheopeningcurtain.
Forlowvoltagelockoutsituations,thereisa Reset
CircuitwhichresetstheCPUwhenvoltagegoesabove
2.90vornewbatteriesareinstalled.Thisfeature
eliminatesthemanualresetfunctionnecessaryonOM-2
models.IC-102willwaittoseeifvoltagerisesto2.90v,If
itdoes,thereleasecyclecontinues.
Settingthespeedringtomechanical"60"or"B"
overridesIC-102'scontrolso theshutteris releasedby the
mirror.
ExposureControl
Hereisa listofexposuremodes, allofwhichare
aperturepriorityormanual.
1,Automaticbyaveragelightmeasurement.Thisis
essentiallythesameoff-the-filmmethodas usedby
OM-2andOM-10.
2Automaticbyspotmeasurement.Unlikethe
OM-2,exposureiscalculatedinadvance,
3. Automaticby memory,whereinan exposureis
repeatedonallsubsequentexposuresforuptoan
hour.
4.Manualbyaveragelightmeasurement,whichis
similartomatchneedleonlywithanLCDbargraph
insteadofa needle.
5.Manualbyspotlightmeasurement.
6.Anymodeusingspotmeasurementcanbewitl
highlightorshadowcompensation.
7.Off-the-filmflashexposurecontrol.
Whereandhowalloftheseoptionsareusedisthe
operator'sprovince.Oursistoknowhoweachmode
functionsfromanelectricalstandpoint.
1.AutomaticbyAverageLight
ASAistheonlyexposurecomponentneededin
advanceforthisexposuremode.Subjectbrightnessand
aperturearestillmeasuredpriortoexposure,butareonly
usedfordisplaypurposes.
AsthemirrorrisesandtheICsprepareforexposure,
voltagetooneinputofcomparatorCP-MinsideIC-102
issettoa valuebaseduponASA.Thesecondinputis
connectedtotheintegrationoutputfrompin10,IC-103.
BecauseIC-102hasnotsignaledIC-103tostart
integration,voltageatthesecondinputissetlow.
Nowthemirrorisupandtheaveraginglight
photodiode(SPD-A)islookingattheopeningcurtain
whichispaintedtohavereflectivityequaltofilm.IC-102
—aftercheckingbatteryvoltage— firesmagnetMG-1to
releasetheopeningcurtain.TriggerSwitchSW-103
openstosignalmovementofthecurtain,(Thereisan
adjustabledelaycircuitwithC-101andVR-102tosetslit
widthatfastspeeds.)Lightfromthesubjectisfocusedon
theopeningcurtain(andlaterthefilm)throughthe
stopped-downlens,A portionofthislightreflectsbackto
thephotodiodeonIC-103,
IC-102initiatesintegrationofreflectedlightwithtime
(theequivalentofexposure)witha signalfrompin80to
pin14,IC-103.Voltageontheintegrator'soutputbegins
toincreaseata rateproportionaltolightintensityatthe
filmplane.Thesamevoltageappearsonthesecondinput
ofcomparatorCP-M.Whenvoltagelevelsatbothinputs
ofCP-Mareequal,exposureforthatparticularfilmis
correct,CP-Mswitchesstatesandthevoltageatpin57,
IC-102fallstozero.
Pin57isconnectedtotransistorQ-202ontheshutter
board,Q-202stopsconductingcurrentthroughmagnet
MG-2whichhasbeenlatchingtheclosingcurtainandthe
exposureends.Asthemirrorreturns,SW-101opensto
resettheICsintometeringmode,
2.AutomaticbySpotMeasurement
Withthemodesetto"Auto,"pressingthe"Spot"
buttonchangesexposurecontrolfromoff-the-filmtoa
typeusingdigitalmemory.Partofthelightfromthe
portionofsubjectcoveredbythefocusingareaofthe
viewfinderscreenisreflectedtothespotphotodiode
(SPD-S).TheCPUcontrolswhichphotodiodesareused
accordingtomode.SPDselectionisthroughpins6 and
7,IC-103.
IC-102convertsBVvoltagealongwithapertureand
ASAdatatoa binarycode,thensendstheinformationto
theCPUinsideIC-101.Subjectbrightnessatthemoment
theSpotButtonwaspressedisstored;however,changesi
apertureandASAwillstillaffectautoshutterspeed.
EachtimetheSpotButtonispressed(beforeexposure)a
newspotreadingisaddedtotheexposurecalculationand
averagedwithpreviousreadings.Theprocesscontinues
untila totalof8 spotreadingsaretaken,thensubsequent
measurementscausethefirstreadingstodropoff.
Whenthereleasebuttonispressedandthemirror
closesSW-101,thelastexposureindicatedbythebar
graphinthedisplayisstoredinIC-101'sdigitalmemory,
TheCPUsendsanexposureprogramtoIC-102tellingit
toignoreIC-103'soff-the-filmintegrationandinsteadto
setupitsownintegration.CapacitorC-104,connectedto
pin44,IC-102,willbechargedbya constantcurrent.
Magnitudeofthecurrentissetproportionaltothe
shutterspeedcalculatedbytheCPU.Binaryspeed
informationisdecodedbyIC-102(DAC)toanalog
voltages.Fasterspeedscallforhigher currents.
WhentheTriggerSwitchopens,currentfromIC-102
beginstochargecapacitorC-104,VoltageonC-104is
alsoconnectedtooneinputofcomparatorCP-M,the
sameasusedforoff-the-filmexposure.Whenthevoltage
reachesa presetlevelequaltothatonCP-M'sother
input,thecomparatorswitchesstatestoturnoffQ-202
andreleasetheclosingcurtain,
AsthemirrorreturnsandSW-101opens,theICsare
resettoautoexposureusingaveragelightreadings.
OLYMPUSOM-4,PAGE2

3.AutomaticbyMemory
Closingthe"Memory"switchineitherautomatic
modeinstructstheCPUtostorethebrightnessreading
usedinthelastexposure.Thatis,aftertheshutterhas
run,thesamespeedwillbeusedforallsubsequent
exposuresregardlessoflightconditions.Changesin
apertureandASAwillcausecomparablechangesin
shutterspeed.Theconditionwillremainforaboutone
houroruntilthe"Clear"switchisclosed,
ThefirstAuto-by-AverageexposureinMemorymode
willbeoff-the-filmusingIC-103'sintegratorAllother
exposureswillbecontrolledbyIC-102inthesame
mannerasforAutobySpot.
4.ManualbyAverage
Manualspeedsareselectedbyturningthespeed
selectorringbehindthelens.A variableresistor
(TV-VR)undertheShutterBoardisturnedbya gear
coupledtothespeedselectorring.Inmanualmodethe
CPUinstructsIC-102toconvertvoltagechangesfrom
theTV-VRtobinarycodealongwithvoltagechanges
frombrightness,aperture,andASA.
TheCPUcalculatesproperexposurebaseduponASA
andlight.Thedifferencebetweenthecorrectexposure
andthatresultingfromapertureandspeedsettingsis
indicatedbythebargraphintheviewfinderdisplay.
Whenthetwoareequal,theendofthebargraphisatthe
indexmarkinthecenter.
ShutterspeediscontrolledbyIC-102inthesame
mannerasAutobySpot.ThecurrenttochargeC-104is
proportionaltothemanualspeedselected.
5.ManualbySpot
ExposurecalculationsbytheCPUarebaseduponan
averageofuptoeightspotlightreadings.Thebargraph
indicatestheresultofthisaverage,Shutterspeedcontrol
isthesameinallmanualmodes,sincethespeedselected
willbeusedregardlessofexposureerror.
6.HighlightandShadow
Inany"Spot"modeofoperation,pressingthe"Hi,
Light"or"Shadow"switcheswillchangetheindicated
exposure."Shadow"shortensexposuretimebyabout2 1/2
Ev,while"Hi.Light"extendsexposuretimeby2 Ev.In
automodes,theactualshutterspeedischanged
accordingly,
7-Off-The-FilmFlashExposureControl
Whena suitableflash,suchastheT-32,isinstalledon
thecamera,operationchangestoOff-The-FilmFlash
mode.Allothermodesareclearedbytheflashoperation.
TheCPUgatherslight,ASA,andapertureconditions,
thencalculatesanexposure.Ifshutterspeedislessthan
1/60,theflashwillbetriggeredduringexposure.Light
fromtheflashisintegratedbyIC-I03,thesameasAuto
byAveragemode.Whena properexposurehasbeen
made,pin48,IC-102goeshighsignalingtheflash
throughitsdedicationcontact.Theflashquenches,the
shuttertimesoutat1 /60second,andthesystemresetsfor
thenextexposure.
Aftera flashexposure,thestrobeLED(viewfinder)
willflickerifexposurewascorrect.Forinsufficientlight,
the"Under"LCDwillflickerandthe"Over"LCDflickers
toindicatetoomuchlight.
TheSyncSwitchdoesnotconnectdirectlytothehot
shoecontact.Whentheopeningcurtainrunstoclosethe
SyncSwitch(X-Contact),pin59,IC-102isconnectedto
thechassisorB+,Pin50,IC-102,thengoeslowtoturnon
transistorQ-101.Q-101switchesB+tothegateofan
SCRwhichturnsontoconnectthehotshoecontactto
thebody.Iftheautospeedwillbefasterthan1/60,the
SCRisnotswitchedonandtheflashdoesnotfire.
Connectingthepositivesideofa 2vpowersourcetothe
shoeandthenegativesidetotheright-sidededication
contactshouldsetflashmodeoperation.TheredLED
indicatingtheflashsymbolwilllightintheviewfinder
andshutterspeedwillbe1/60.
Readout
TheLCDviewfinderindicationisdrivenbyIC-104
situatedundertheflexcircuitbetweentheprismand
rewindshaft.CapacitorC-302betweenpins3 and4,
IC-104,actsasa voltagebooster(+/-3vtoVcc)to
providethenecessary6 voltstooperatetheLCD,Power
(Vcc)issuppliedthroughtransistorQ-301(PNP)which
iscontrolledbypin54, IC-102.
AstheCPUdeterminesexposureandmode,that
informationistransmittedtoIC-104fordecodingand
display,Datatransmissiontakesplaceaboutonceevery
100msthrougha seriesline,
1.DataSyncsignalissentfrompin12,IC-101to
pinllsIC-104.
2.Timingclocksignalissentfrompin10,IC-101to
pin13,IC-104.
3.Seriesdataissentfrompin11,IC-104topin12,
IC-104.
Thedisplayismadeupof41horizontalrowsandback
platesinthreeverticalrows.Voltagedifferencesof4.0v
betweenanyhorizontalandverticalwillresultinthat
segmentbeingdarkened.Thereisa RAMincludedinside
IC-104,
Thereisa backlightlampforviewingthedisplayin
darkconditions.Pressingthe"Lamp"switchsetsthe
lightonforabout8 seconds.
OLYMPUSOM-4,PAGE3

BatteryCheck
TurningtheModeSwitchto"BatteryCheck"sets
IC-101tothecheckcondition.IC-101directsIC-102to
drivethePiezoBuzzerthroughpin25andtheTimer
LEDthroughpin41.Thedisplayisalsoinvolved:
1.Whenvoltageisabove2.75v,thetoneissteady
andtheLCDandLEDaresteady,
2.Whenvoltageisbetween2.65vand2.75v,the
tone,LED,andLCDareintermittent.
3.Below2.65vthereisnoindication.
4.Below1.9vthereisa constantwarningtone.
Rememberalso,whenvoltageisbelow2.65v,releaseis
inhibitedbutwillresetbyitselfwhennewbatteriesare
installed.
WinderDedication
Therearefivewinderormotordrivededication
contactsonthecamera'sbottom.Fromfronttoback
theyconnectasfollows:
1.SFSwitchlocatednearthebatterycase.The
switchisclosed,shortingthecontacttochassiswhen
thereisnofilmonthespool,
2.RKSwitchwhichcloses,shortingthecontactto
chassiswhentherewindbuttonispressed,
3.& 4,MDSwitchlocatednearthecontacts.
Withthemirrordown,thecontactsareshorted
together.Withthemirrorup,#3isopenand#4is
shortedtochassis,
5.U Switchlocatedonbottomrewindside.The
switchcloses,shortingthecontacttochassiswhen
filmdoorisopen.
Self-Timer
ClosingtheTimerSwitch(SW-104)connectspins20
and26,IC-101.Thisprogramsanelectronicdelay
betweenthetimeSW-101closes(mirrorrises)and
whenIC-102signalsMG-1toreleasetheopening
curtain.Thetimerintervalis12secondswithflashing
LEDandbuzzertocallplentyofattentiontothe
situation.
II.EXTERNALTESTS
1.Tryoperatingthecamerainmechanicalmode,"B"
and"60."Thereshouldbenormalshutterand
transportfunction.Ifnot,removethebottomcover,
thenchecktheshutterchargegears,mirrorcharging
lever,andreleaselever.
1MovetheModeSwitchto"BatteryCheck."There
shouldbe audibleandvisual(LED)indications.If not,
testbatteryvoltage.Below2.65vtheLEDandBuzzerwill
notfunction.Ifthevoltageisabove2.65v3theremaybea
powercircuitproblemorpossiblya dirtybatterycontact.
3.SettheModeSwitchto"Auto,"theshutterspeed
controlringto1/125,thenpressthereleasebuttonone-
halfstroke.TheLCDintheviewfindershouldshowa bar
graphandlistshutterspeedsfrom1 through2000,If
thereisnodisplayandnobatterycheckintheprevious
step,thereisa powercircuitproblem.Testpower
consumption,
4.WatchtheviewfinderLCDasyouchangeaperture,
ASA,andscandifferentsubjectbrightnesses.Thebar
graphshouldchangeoneEvforeachEvchangeyou
makewiththecontrols.Ifchangesareerratic,wipersare
dirtyormakingpoorcontact.Ifthereisnochangewith
brightness,lookfortheword"Memo"intheLCD.Ifitis
flashing,memoryhasbeensetMovethecontrolswitch
to"Clear"toresetthesystem.Stillnochangeinthebar
graphwithlightsuggestsa flexorICproblem,
5.IfLCDresponsewasnormalinstep4,pressthe
"Spot"buttonwhilethecircuitsareon.Theword"Spot"
shouldappearandthebargraphshouldremain
unchangedwithlight.Tryseveralmoretestsforspot
meteringondifferentsubjectbrightnesses.Thebargraph
shouldadjusttoanaverageofthesettings.Also4test
"Highlight"and"Shadow"buttons.Finally,movethe
controlswitchto"Clear."The"Auto"modewithbar
graphshouldreappearIfanyfunctionsfail,themost
likelycauseispoorswitchcontactora brokenconnection
tothetopcover.
6.Seeif"Auto"exposure(without"Spot")delivers
speedsneartobargraphindications,(Besuretousefilm
orsimilarmaterialinfrontofpressureplate.)Ifthe
speedssoundfast,checktheaperture.Ifspeedsdonot
matchLCDindications,thereisanoff-the-filmcircuit
problem.
7.Seeif"Spot"modespeedscorrespondtothebar
graph.Ifnotbutthe"Auto"speedsdo,thereisa possible
problemwithIC-102orthevariableresistors.Ifspeedsin
steps6 and7 arebothwrong,thereisa problemwith
MG-2'scircuitorthetimingswitch.
8.Testseveralshutterspeedsin"Manual"mode.Ifthe
speedsareincorrect,but"Spot"speedsarenormal,
suspecttheTV-VRundertheshutterboard.Ifmanual
speedsarenormalbut"Spot"arenot,thereisa logic
problembetweenIC-101andIC-102— probablyanopen
connection.
9.Apply2 volts(—)tothewind-sideflashdedication
contactwiththemodesetto"Auto"andcircuitson.The
"Flash"LEDshouldappearintheviewfinderandthe
shutterspeedshouldbenear1/60.
10.Trytheauxiliaryfunctionssuchasself-timerand
LCDlampswitch.
Finally,alwayskeeptheseimportantfactsinmind:
A."Auto-Average"exposureiscontrolledbyIC-103at
thetime,ofexposureandmaynotbewhattheLCD
indicatesinadvance.
B."Spot"and"Manual"exposuresarecalculatedin
advancebytheCPUandareindicatedbytheLCD,
Thoseexposuresshouldalways equaltheindication.
OLYMPUSOM-4,PAGE4

III.EQUIPMENTANDGENERALINFORMATION
A.Toolsandequipmentneededtocarryouttesting
proceduresinthisguide:
Groundedsolderingiron
DVM
Oscilloscope
Powersupply
Zeroohmtestprobe
1000ohmprobe
B.PowerConsumption:
Allmeasurementsmadewithtypicalcameraconnected
througha DVMtoa regulated2.9vpowersupply.
Circuitsoff(clockon)17micro-amps
Circuitson......................................0,6ma
Shutteropen.........7.5ma
BatteryCheck9 ma
Flashmode6 ma
Self-timer12ma
C.Typicalcoilresistance:
Openingcurtainmagnet,MG-1, . . 54ohms.Measure
betweenQ-201'scollectorandthelegofC-210nearestthe
frontofthecamera.
Closingcurtainmagnet,MG-2..........580ohms.Measure
betweenthebodyandQ-202'scollector,thepinnearest
thefront
D.Preparationfortroubleshooting:
1.AllDVMandscopemeasurementsshouldbemade
withreferencetothenegativesideofthepowersupply.
Forconvenience,youmaywanttosoldera shortwireto
theboardatTP-2,thenusethatasa reference.
2.Mosttestscanbemadewithonlythetopcover
removed.Ifthebottomcoverisremoved,youwillneedto
connecta powersupplyorusea cut-offbottomcoverto
holdthebatteries.
3.Usea straplugforB+orVccsource.
4.Ifyouneedtopowerupthecircuitswithlensoff,first
pressthesmallblackbuttonneartheredindexdotonthe
bayonetring.
5.Removethecoverplateinfrontunderthemirrorto
gainaccesstoMG-2andtheshutterboard,
6.TheindexmarkstraighttothebackontheASA
resistorisASA100.Zeroexposurecompensationisthe
markattwoo'clock.
7.Withthetopremoved,logicswitchesfor"Spot,"
"Clear,""Memo,"etc.,aredisconnected.Toprogram
thosemodes,usetweezertipstomomentarilyconnect
wiresolderpadsorpinsonIC-101asindicated:
"Spot"GraytoRedorPins16and17
"Memory". YellowtoBrownorPins18and14
"Clear"....YellowtoRedorPins16and18
8.ThecircuitmaybeclearedbymovingtheMode
Switchtothebatterycheckposition.
9.TakecaretoavoidstaticelectricitydamagetoICs
whencoversareoffthecamera.
10.Takefulladvantageofthecomprehensiveviewfinder
LCDtoaidyourtroubleshooting.Checkeachfunction
todeterminewhatworksandwhatdoesn't.ESTABLISH
THEEXACTSYMPTOMSBEFOREYOUBEGIN
TOTROUBLESHOOT
IV.ADJUSTMENTPROCEDURE
Triggerdelay(TimingSwitch),BV,andDirectEv
adjustmentscanbereachedthrougha cutoutinthefront
plateabovetheSelf-TimerSwitch,
Ifpossible,usea powersupplyinsteadofbatteriesduring
adjustment.Setsupplyvoltageat3.0v.
1.Testmanualspeedsat1/8(117ms,+/-0)and1/2000
(0.49ms,+/-0.2ms).Adjust1/8speedwithVR-101.
Adjust1/2000speedwithVR-102,thetriggerdelay
underthefrontleathernearestthewindside.
2.SetASA100,f-5.6,andLV-10,andmodeto"Auto."
Besure"Spot"modeisnotusedandexposurecorrection
factoron ASAdialis zero.Usefilm or surfaceofsimilar
reflectivityontestersensorface.
Tryseveraltestexposures,thenadjustfornearzero
exposureerrorusingVR-110,underthefrontleather
nearestthelens.ChecktheexposureathigherASAs(up
to3200)andfinetuneifnecessaryusingVR-103,Tryto
maintain+/-0.3EvoverASArange.
3.SetASA100,f-4,"Auto"(not"Spot")andLV-11.
AdjustVR-105,underthefrontleatheratthecenter,so
theLCDbargraphindicates1/125.
4.SetASA100,f-4,"Auto,"andLV-11.Pressthe
"Spot"button;theindexdotshouldindicate1/125.
AdjustusingVR-106
5.Ifautoexposurein"Spot"modeisnotcorrect,DAC
referencevoltagemaybeincorrect.SetASA3200,
correctionfactortozero.Usinga DVM,measurethe
voltagebetweenVref(DVMcommonlead)andDAC
outputatpin46,IC-102,Atroomtemperature,21
degreescentigrade,thevoltageshouldbe198mv,Adjust
withVR-108.
OLYMPUSOM-4,PAGE5

V.ICCHECKS
IC101
Pins1,2,3.Batterycheckmodesignalsoutputs.Voltage
isnormallynearzero,
Pins4,5,6.ControltoIC-102forwhichsignalsshouldbe
decoded.Typicaltracesshown,
Pins7,8.Integrationcapacitorselectioncontrollines.
Setscodeforselectionduringrelease.Totest,applyVcc
toSW-101wirethrough1000ohmprobe.ASA6,pin7
low,pin8 high.ASA100,pin7 high,pin8 low,
Pin9 hasnoconnection,
Pins 10,11,12. Exposureoutput to LCD, Pin10is timing
signal,pin11isserialdata,andpin12issync.Seescope
traces.
Pins13to20areinputsfromlogicswitches,("Mode,"
"Clear,"etc,)Commonlinesarepins17,18,and20.
Pins21and22arebatterynegative.
Pin23hasnoconnection.
Pins24,25,26. Momentarilyconnectingeachtopin20
setslampon,batterycheck,orself-timer.
Pin27istheinputfromIC-102tosetflashmode.Vcc
througha 1000ohmprobeshouldsetflashsymbolon
LCD.
Pin28istheflashLEDinput.
Pin29istheexposuredatafromIC-102,Seescopetrace.
Pin30istheinputfromIC-102tosignalSW-101closed
(mirrorup).Firsthighstoresexposuredata,nexthigh
returnstometeringmode.Youcandrivethecircuit
bonkerswithrandomhighstopin30,
Pin31isoutputtoMemoryLEDon"Spot"button.
Pin32isoutputtoQ-105tooperateLCDbacklightlamp,
Pin33isoutputtoQ-106forstrobeLEDinviewfinder.
Dependsuponinputatpin28.
Pin34isoutputtoIC-102toturnonbatterycheckLED.
Shouldgohighin"Check"modeifsupplyisabove2.75v.
Pins35to42areDACoutputlinestoIC-102,Seescope
traces.
Pin43isinputfromresetcircuit,Vccresetscircuit,
Pins44and45are500KHzclocksignal,probablyfor
CPU,
Pin46isVccin.
Pins47and48connecttothequartzcrystal.32,8KHz
sinewave,
Pin49isMirrorSwitch,SW-101,signalinput.Goeslow
asSW-101closes.
Pin50isthesameaspin27.
Pin51isbatterynegative.
Pin52isCLKoutput.
Pin53isthepowersignaltoIC-102forallcircuits.Series
ofhighpulsesafterreleaseispressedone-halfstroke.
Pin54issignaltoIC-102tosupplypowertoLCD.High
whenon.
Pin55isoutputtoIC-103thatsetsphotodiodeaccording
tomode.Highis"Average,"lowis"Spot."
Pin56signalsIC-103withlowwhenSW-101closes,
Pin57isintegrationcompensationtoIC-102.
Pin58isPiezosignaltoIC-102.
Pins59and60aresignalstoIC-102tochargeMG-l's
capacitorandrelease.Lowsignalsrelease.
OLYMPUSOM-4,PAGE6

IC-102
Pin1 islimiteroutputtoIC-103'sintegrator,Iflightis
above1/2000exposure,pin! goeshightosetexposure
timeto1/2000,
Pin2 hasnoconnection,
Pin3 isIC-103'sintegratorinputtoCP-M.Vccthrougha
1000ohmprobeshouldcausefastspeedin"Auto."See
scopetrace,
Pins4,5 switchintegrationcapacitorsintoIC-103's
circuit.Normallylow.
Pin6 isground.
Pin7 isBVinputfromIC-103.l,5vto1.7v,I8mv/Ev,
Pin8 connectstopin15,IC-103;SPDanode.Typical
voltageis1.8v.
Pins9 and10areintegrationcapacitorcontrolcodefrom
CPU.Seepins7 and8,IC-101.
Pins11,12,13aredecodingcontrolinputsfromCPU.
Seescopetraces.
Pins15and16arebatterycheckmodeinputsfrompins1,2,
IC-101.
Pins17and18areMG-l'scontrolsignalsfromtheCPU.
B-througha 1000ohmprobeshouldcauseM-lto
"click."
Pin19isthePiczoinputfromCPU.
Pin20isintegratorcompensationinputfromCPU.
Pins21and22aremodecontrolfromCPU,(Pins56,55,
IC-101.)
Pin23issignalfromCPUtopowerLCD.
Pin24is"poweron"signalfromIC-101.Shouldgohigh
whenreleaseispressedone-halfstroke.
Pin25isCLKin.
Pin26isB-,
Pin27isresetsignaltoIC-101whenbatteryvoltage
comesupto2.90v,
Pins28to35areDACdatafromIC-101.Seescope
traces.
Pin36isinputsignalforLED.Vccthrougha 1000ohm
probeshouldlightLED.
Pin37istriggeroutputtoCPU.
Pin38isEvdataouttoCPU.Seescopetrace,
Pins39and40areoutputstoCPUtoindicateflashison
(40)andcharged(39).Pin39voltageshouldfallfrom
nearVcctonearzerowhenflashcharges.(B-through
1000ohmprobetopin48),
Pin41isSelf-TimerLEDdrivesignaltoQ-40I.Voltage
nearzerototurnonLED.
Pin42isthe"go"signaltoCPUifbatteryvoltageisabove
2.65v.Seriesoflowpulsesstopwhenbatteryvoltageis
low.
Pin43connectstoC-105.
Pin44isintegrationcurrentchargingC-104for
"Manual"and"Spot"shuttertiming.Seescopetrace.
Vccthrougha 1000ohmprobeshouldresultinfast
manualspeed.
OLYMPUSOM-4,PAGE7

Pin45ismanualspeedcalibrationinputfromVR-101.
Vccthrough1000ohmprobeshouldresultinfastspeed,
Pin46isDACoutput.Seescopetrace.
Pin47isflashmodesignalfromshoecontactB-through
1000ohmprobeshouldsetflashmode.
Pins48and49areTTLflashexposureoutput,
Pin50issyncsignaloutputtotriggerflash.Shouldpulse
lowwhenfirstcurtainruns.
Pin51isVccin.
Pin52isPiezodrivesignal.Seescopetrace,
Pin53isCLKouttoIC-104,
Pin54ispowersignaltoIC-104.Shouldbelowtoturnon
display.
Pin55isTriggerSwitchinput.Shouldpulselowasfirst
curtainruns.Vccthrougha 1000ohmprobeshouldcause
shuttertolatchopen,
Pin56isreferenceforTriggerdelay.
Pin57isoutputtoQ-202tooperateMG-2.Shouldgo
highduringexposure,allmodes.
Pin58isinputfromResetCircuitVoltageshouldpulse
highasmirrorrises.
Pin59isinputfromX-syncSwitch.Voltageshouldbe
zerowithshuttersetandhighafterfirstcurtainhasrun.
Pin60ischargesignaltoC-201,forMG-1.Voltagewill
pulsehighatrelease,thenfalltonearzerotorechargeC-
201.
Pin61isreleasesignaltoQ-201forMG-1.Pulseslowfor
release.
Pin62isB-in.
Pins63and64areoffsetcompensation.Voltageisnear
zero.
Pin65isreferenceadjust.Voltageisabout30mv.
Pin66isexposurecompensationreferencecurrent.Near
2.7v.
Pin67isASAinput.Seescopetrace.Voltageisnear2.7v,
Pin§68and69are"Auto"adjustconnections.Voltageis
near2.7v.
Pin70DACreferenceadjustvoltage.Typicalisnear
1.8v.
Pins 71and72are reference current to TV-VR.Typical
voltageisnear1.8v.
Pin73isinputfromTV-VR.Seescopetrace.B-through
a1000ohmprobeshouldresultinfastmanualspeeds.
Pin74isinputfromAV-VR.Typicalvoltageisnear1.8v,
B-througha 1000ohmprobeshouldsendbargraphfull
scale.
Pin75isAV-VRreferencecurrentTypicalvoltageis
1.8v.
Pin76inputfromlockvoltageadjustmentTypical
voltageisnearl.8v.
Pins77to79aretoBVadjustmentcircuit.Typical
Voltagesarenear1.3vto77and78,Nearzerofor79.
Pin80isTriggerSwitchsignaltoIC-103.Shouldpulse
lowduringexposure.
OLYMPUSOM-4,PAGE8

,ir-i03
IC-104
This1Clivesbeneaththemirrorboxfloorandcanonly
bereachedbyremovingthefrontplate.Itsoutputsare
BV(measuredatpin7,IC102)andintegration
(measuredatpin3,IC-102).Ifthesearecorrect,the1Cis
probablyworking.Ifnot,youmaywanttoremovethe
frontplate,thencheckconnectionsaccordingtothe
drawing,
Pin16istheBVoutputmeasuredatpin7,IC102.
Typicalvoltageisl,5vto1.7v,18mv/LV.
Pin10isintegrationoutputmeasuredatpin3,IC-103.
Seescopetracefor"Auto"mode.
This1Clivesundera circuitboardbetweentheprismand
ASAresistor.Itisnoteasytoreachfortests,but
importantinputscanbecheckedatICs101and102,Its
output,of course,is theLCD,
Pin1 isCLKinput,Checkatpin53,IC-I02andthewhite
wire,
Pin5 isVccinfromIC-102.Checkatpin54,IC-102.
Pin6 isB-,
Pin11isdatasyncsignalfromIC-101.Checkscopetrace
atpin12,IC-101andthegreenwire.
Pin12isserialdatain.CheckscopetraceatpinII,
IC-101andtheyellowwire.
Pin13isdataclocksignalin.Checkatpin10,IC-101
andthebluewire.
Ifthereisnodisplay,checkforproperconnectionsto
pins3 and4andfromtheretocapacitorC-3Q2.Thisisthe
6-voltpowersourcefortheLCD,
OLYMPUSOM-4,PAGE9

V.TROUBLESHOOTING
TROUBLESHOOTINGFLOWCHARTINDEX
Camerasymptom
NoLCD
Nobatterycheck
Noshutteroperation
Excessivebatteryusage
LCDbargraphhighorover
"SpotAuto"speedsfast
"Auto"speedsfastornormal
"Manual"speedsnormal
LCDbargraphloworunder
"SpotAuto"speedsslow
"Auto"speedsslowornormal
"Manual"speedsnormal
LCDbargrapherratic
"SpotAuto"speedserratic
Manualspeedsnormal
Shutterwon'trun
Mirrorreleases,staysup
LCDnormal
Mechanicalspeedsnormal
Shutterwon'trunafter
firstreleaseunlessreset
Shutterstaysopen"Auto"
and"Manual"
Mechanicalspeedsnormal
LCDnormal
Shuttersloworopenin
"AutoAverage"mode
"Manual"and"SpotAuto"
speedsarenormal
LCDnormal
1-A
1-B
2-A
2-B
2-C
3-A
3-B
4-A
4-B
Shuttersloworopenin
"Manual"and"SpotAverage"
"AutoAverage"speedsnormal
LCDnormal
Shutterfastorrunning
through,"Auto"and"Manual"
LCDnormal
Mechanicalspeedsnormal
Shutterfastin"AutoAverage"
"Manual"and"Spot"speeds
arenormal
LCDisnormal
Shutterfastin"Manual"
and"SpotAuto"
"AutoAverage"speedsnormal
LCDisnormal
"Manual"speedsincorrect
"Auto"speedsnormal
LCDweakornotworking
Shutterfunctionsnormal
Exposurenormal
LCDshowswrongcharacters
Exposureisnormal
Flashwillnotfire
Shutterfunctionsarenormal
Flashcontrolproblems:
seeIC-ChecksandCircuitDescription,
Self-Timernotworking
LEDorPiezoBuzzerare
notfunctioning
Self-Timerdelaynormal
Flowchart
4-C
4-S
4-E
4-F
4-G
5-A
5-B
6-A
7-A
7-B
OLYMPUSOM-4.PAGE10

1.PowerCircuitMalfunctions
A.ExternalObservations
No LCD,
Nobatterycheck.
Noshutteroperationexceptmechanical
OLYMPUSOM-4,PAGE11

B.ExternalObservations:
Batteriesrundownquickly,
Shutterfunctionsmayormaynotbenormal.
LCDmayormaynotfunction.
OLYMPUSOM-4,PAGE12

2.MeteringCircuitMalfunctions
A.ExternalObservations:
Bargraphindicationsarehighor"over."
"Spot-Auto"speedsfast.
"Auto"speedsfastornormal
"Manual"speedsnormal.
OLYMPUSOM-4,PAGE13
B.ExternalObservations:
Bargraphindicateslowor"under."
"Spot-Auto"speedsslow,
"Auto"speedsslowornormal
"Manual"speedsnormal.
First,checkbargraphresponsetolight,ASA,andAV
changestoisolateproblem.Followthesamepro-
cedureas2-A,butlookforthefollowing:
1,Lowvoltageatpin7,IC-102.
2,OpenconnectionstoVR-105andVR-106,
3,Openconnectionto,orpoorcontactof,AV-VR
wiper.
4,SolderbridgearoundSV-VRterminalsorshorted
wiring,
5,Shortbetweenpins67,68,69,IC-102.

C.ExternalObservations:
Erraticbargraphreadings.
"Spot-Auto"speedserratic,
"Auto"and"Manual"speedsmaybenormal,
1.CapacitorC-108(filter)maybeopenornot
soldered.ItisnearIC-103butalsoconnectsacross
pins7 and8,IC-102.Valueis0,015MF.
2.CheckifbargraphisstableinBCmode.Ifso,
checkR-130,nearIC-101.
3.CheckfordirtywipersonAV-VRandSV-VR,
3.ReleaseMalfunctions
A.ExternalObservations:
Shutterwillnotrelease(orerratic)in"Auto"
or"Manual,"althoughmirrorisup.
Mechanicalshutterfunctionisnormal
LCDisnormal.
Supplyvoltageisabove2.65v.
OLYMPUSOM-4,PAGE14

B.ExternalObservations:
Shutterreleasesonce,thenwillnotrelease again
untilcircuitisreset,
LCDnormal.
4.ShutterMalfunctions
A.ExternalObservations:
Shutterstaysopenin"Auto"and"Manual"
MechanicalspeedsOK,
LCDnormal.
OLYMPUSOM-4,PAGE15

B.ExternalObservations:
Shuttersloworopenin"AutoAverage."
Manualspeedsnormal.
"Spot-Auto"speedsnormal
LCDnormal
C.ExternalObservations:
Shuttersloworopenin"Manual,"
Shuttersloworopenin"SpotAuto,"
"Auto"speedsnormal
LCDnormal.
Note:BesureLCDindicatescorrect
"Manual"speed.Ifnot,TV-VRis
dirty.
OLYMPUSOM-4,PAGE16

D.ExternalObservations:
Shutterfastorrunsthrough"Auto"and
"Manual"
LCDisnormal,
Mechanicaloperationisnormal.
OLYMPUSOM-4,PAGE17

E.ExternalObservations:
Shutterfastin"AutoAverage."
"Manual"and"SpotAuto"speedsnormal
LCDisnormal
F.ExternalObservations:
Shutterfastorrunsthroughin"Manual"or
"AutoSpot."
"AutoAverage"speedsnormal
LCDisnormal.
G.ExternalObservations:
"Manual"speedsnotcorrectorwon'trespond
toadjustment.
"Auto"modespeedsOKt
1.Checkeach"Manual"speedwithLCD.IfLCD
doesnotcorrespondtospeeddial,TV-VRisdirty
ornotmakingcontact.
2.Ifslowspeedsareoff,checkVR-101soldering.
3.Iffastspeedsareoff,check:
A.VR-102
B. R-102
C. C-102
D.TriggerSwitchchatter
E.Curtainoverlap
OLYMPUSOM-4,PAGE18

5.DisplayMalfunctions
A.ExternalObservations:
NoLCDorweakorerratic,
Shutterfunctionsnormal.
Exposureisnormal.
OLYMPUSOM-4,PAGE19

B.ExternalObservations;
LCDworks,butdisplayswrongcharacters
formode.
Shutterfunctionappearstobenormal.
Lookforpoorsolderconnectionsatwires
toDisplayBoard.
6.FlashMalfunctions
A.ExternalObservations:
Flashwillnotfire,
"Flash"modeselectedOK.
OLYMPUSOM-4, PAGE20