Revox B225 Technical specifications

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REI/QX ' . B225
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1.GENERAL
1-1IndexofCOolayercontrols1/i
1*1* 1 Generalcontrols1/1
1*1*2Specialcontrols1/2
1*1*3Rearpanelconnectors1/3
2.
t REMOVALOFASSEHBLIES
2.1Removingthetopcover2/1
2*2Removingtnesidepanels2/1
2.3Removingtheindividualcircuitboards2/1
2*4Removingtheplayermechanism2/1
2®5Removingthedisplay2/2
2*6Removingthepo^er t r ansformator2/2
2*7Removingthedrawermotor2/1
2*8Removingtneoperatingpanel2/3
Z«9Removingtheguiderods2/3
3*CIRCUITDESCRIPTIONS
3.1SERVO1 PC31.759.3103/1
3.1®1Stabilizationofthesupplyvoltages3/1
3*1*2 Orawerpositiondetector3/1
3*1.3Focuscontrolloop3/2
3*1*4 Oiscmotorcontrolloop3/2
3.2MicroprocessorPC3 . 1.769.3203/3
3.2*1 Microprocessorsystem3/3
3^2*2 Drawermotorcontrol3/4
3*3SERVO-2 PCP1.769*3303/4
3.3^1Radialcontrol3/4
3*3.2 Radialcontrolcircuit3/4
3*3*3 Automaticgaincontrol-{AGC-}circuit3/5
3«3r-4Offsetcontrolcircuit.3/5
3.3.5Trackdetectingcircuit3/6
3*4PreamplifierandlaserPCB1*769*100*353/6
3.4.1Lasercontrol3/6
3*4^2 Focusand radialcontrolsignals3/6
3«4*3HFsignalamplifier3/6
3.5DecoderPChl-7o^.3003/6
3* t> • 1 Digitalsignalprocessing 3/7
3»5«2Digitalsine-wavegenerator3/7
3. 5.J HFLand 0-Jdetector3/7
3*oOACTC31.769.23 3 3/7
3.t».l digitalfiltering(oversampling)and0/Aconversion3/7
3*6.2 Leveladjustmentandheadphonesamplifier3/3

mmmm eel/ox B225
*•TESTPOINTStADJUSTMENTSOH E225
4i Testpointson622^4/1
4«-l»lTestpointsonSERVOI PCB1«?69*3104/1
4.1.2TestpointsonSERVO2 PCB1.769.3304/3
4.1.3TestpointsonmicroprocessorPCB1.769*3204/4
4.1.4TestpointsondecoderPCB1.769.3004/6
4.1.5Testpointson0AC-PCB1.769.2604/8
4®2AdjustmentsonCOplayerB2254/9
4.2.1Aids4/9
4.2.2Aligningtheplayermechanism?general4/9
4*2®3 Adjustingthelasercurrent4/9
4.2.4Adjustingthebalance4/9
4«Z*5Adjustingthefocusgain4/10
4*2*6 Checkingthe-tinglealignment4/10
4*»2#7 AdjustingtheDCcomponentofthefocussignal4/11
4.3Measuringtheaudi.odata4/11
4*3.1 A i 4s 4/i1
4*3#2 Harmonicdistortion4/11
4.3.3Outputlevel4/11
4.3*4 Frequencyresponse4/11
4.3.5Crosstalk4/12
4.3.6Signal-to-noiseratio*linear4/12
4.3.7Signal-to-noiseratio?weighted- ' 4/12
4.3.3Phaselinearity4/12
4.4ListeningtestwithreferenceCO4/12
5*DIAGRAMS
6.SPAREPARTS
7* TECHNICALAPPENDIX
7.1Technicaldata7/1
7«Z Dimensions7/2"

R^/ax B225
1.
1.1
GENERAL
IndexofCDplayercontrols
1.1.1 Generalcontrols
1IjPOWER*
[ 2 j LOAD
[ 3 J STOP*
[ 4 J PLAY/NEXT
H5"fREPEAT
[6j(CDdrive)
[7j(Display)
[8j(keys0-9)
KeyforswitchingtheCDplayerONand
OFF. However,certainassemblies(such
astheIRreceiver)remainalwaysswitched"
on(inso-calledstandby mode).
Thedrawerwiththeplayermechanism
[6jopensorcloseswhenthiskeyis
pressed.
Interruptstheplayerfunction.The
opticallaserheadisretractedtothe
startingpositionandtheprogramis
cancellediftheCDplayerwasinprogram
mode. Thepositioninwhichthelaser
pickupwasoperatingbeforeSTOPwas
pressedcannotbereproduced.Ifthis
isdesired,pleaserefertotJL (PAUSE)
key.
Playkeywiththefollowingfunctions;
IfpressedafterLOAD[2j,theCDstarts
torotate,thecontentlistisread,and
thediscisplayedstartingatthefirst
selection (TRACK). Thenextselection
(TRACK)isaccessedwhenthiskeyis
pressedagain.
IfpressedafterPROGRAMMODE[26 J has
beenselected:playprogrammodeis
activated.
Theselectioncurrf.r^lybeingplayed
isrepeatedimmediatelywhenthiskey
ispressed.IftheCDplayerisinSTOP
mode, thefirstselectionofthecompact
discwillbeplayed.IftheCDplayeris
inprogrammode,thecurrentprogramstep
willberepeated.
DrawermodulewithCDplayermechanism
andliquid-crystaldisplay.Thedrawer
canbeopenedorclosedwithLOAD[2].
MultifunctionLCdisplay'whichprovides
informationonalloperatingmodesof
theCDplayerandthecontentofthe
loadedcompactdisc.
Digitkeysfordirectaddressingof
aselection(TRACK)inconjunctionwith
PLAY/NEXT[4j,orforprogramming.
TheCDplayercanbeswitchedonbypressinganyof
thecontrols [ Ijthrough[8joftheupperrow(except
REPEAT[5jandthedigitkey0).TheCDplayerstarts
intheselectedoperatingmode.

mruim REVOX B225
1.1.2 Specialcontrols
Thecontrols inthe lowerfront-panelsection canbe
roughlydividedinto two functiongroups:controls
forsupplementaryplayerfunctions, and programming
controls.
AControls for supplementaryplayerfunctions
[9]PHONES
[10]VOLUME +
[11jVOLUME -
[12] CAL TONE *
13]AUTOSTOP
[14j Key•
[15J VA (pause ) *
[16] « key
[17]DISPLAY
HeadphonesjaGksocket for headphones
200 to600 ohms.
Increases the headphoneslevel
and the level ofthe VARIABLEOUTPUT.
Decreases the headphoneslevel
and the level ofthe VARIABLEOUTPUT
Thiscalibrationbuttonconnects a
1000 Hz calibrationtone tothe
outputs so that the recordinglevel
of a connectedtapedeck canbe
accuratelyadjusted. The1000Hz
CALTONEcorresponds tothe maximum
outputlevel.Thismaximumlevel
issystem-dependent and will not
beexceededeven by shortpeak
pulses.
Interrupts the playingsequence
at theendofthe currentselection
orprogramstep. The laserpickup
isautomaticallypositioned at
thebeginning ofthe nextselection.
Thenextselection is started
immediatelywhenPAUSE TA[15]is
pressed.Uponconclusion of this
selection, theCD playerswitches
again to PAUSEmode.
Repositions the pickupfrom any
locationtoward theend.
Interrupts the playingsequence
at any time.
Repositions the pickupfrom any
locationtoward the start.
Switchesover the displaymode.
Thetimeelapsedsince the start
of the currentselection is displayed
innormalPLAYmode. The total
playtimefrom the start tothe
currentselection canbe displayed
bypressingthis key.
Thesefunctions can also be programmed.
PROGRAMMINGkeys
18]LOOP *
19] +
[20] -
[21] IR SENSOR
[22]STORE
[23]MARK
[24]TRACK/TIME
CommandkeyforrepeatingtheCD
ortheproqr^4«untilSTOP[3jis
pressed.
Forward"paging"inprogrammode.
Particularlyusefulformodifying
anexistingprogram.
Samefunctionas[19]butbackward
paging.
Infraredreceiverwindow
Memoryloadkeytobepressedafter
eachprogramstepentry.Thenext
programstepissubsequently
displayedsothatthecorresponding
entriescanbemade.
Allowsa startanda stopmark
tobesetinprogrammingmodewhile
aselectionisbeingplayed.Any
CDlocationcanthusbeprogrammed.
Switchesthedisplayinprogramming
modefromselection(track)input
totimeinput(minutesand seconds).

mWU\n)MPd R^OX B225
[25jCURSOR
[26J PROGRAM
1.1.3Rear-panelconnectors
[30]AUDIOOUTPUTFIXED.Outputforconnecting
anamplifieronwhichtheinputcanbematched
totheleveloftheCDplayer(theREVOXB251
amplifierisideallymatchedatthe factory).
[31]AUDIOOUTPUTVARIABLE.Activespeakersor
anoutputstagefetc.canbeconnecteddirectly
tothisoutput.Thevolumecanbeadjusted
withVOLUME+ and- onthefrontpanelof
theCDplayer.
[32]ACPOWER.Powerinlet(thesettingofthe
linevoltageselectorcanbecheckedadjacent
toit ) .
..[33J • " REMOTE.Thisconnectorcanbeusedfor:a)
disablingtheIRreceiverandb)connecting
acable-typeremotecontroldevice.
Anypositiononthedisplaycan
beeditedbyapproachingitwiththe
cursor. NOTE;ifthedisplayisin
TIMEmode,thecursormustbe
advancedwiththiskeyinorderto
enterthesecondsaftertheminutes.
Setstheprogramentrymode.If
PLAY/NEXT[4Jispressedafter
theprogramentrieshavebeen
completed,theCDplayerstartsin
PROGRAMmode,
IftheCDplayeristobestarted
innormalmodeaftertheprogram
entrieshavebeencompleted,press
thePROGRAMkey [ 26J againbefore
PLAY/NEXT[4].

B^OX B225 SECTION2/1
2 . REMOVALOFASSEMBLIES
Important:
DisconnecttheCDplayerfromtheACsupplybefore
removinganypartsofthehousing..Forcertainwork
itisnecessarytoopenorclosethedrawermodule.
Thiscanbedonemanuallywithoutdamagingtheunit.
2.1Removingthetopcover
-Unfastenfivescrews[AjontherearoftheCDplayer.
-Withdrawcovertowardtherear.
2.2Removingthesidepanels
-Unfastentwoscrewsoneachsidepanelinorderto
removethem.
2 . 3 Removingtheindividualcircuitboards
Thecircuitboardsareaccessiblewhenthetopcover
isremoved(Section2.1).
Thecircuitboards1.769.280(DACPCB),1.769.300
(DECODERPCB),and1.769.330(SERVO2 PCB)canbepulled
outoftheinterconnectionboardafterthefixingscrews
[B]havebeenunfastened.
FourconnectorsmustbedetachedbeforethePCB1.769.320
(MICROPROCESSOR)isremoved.Thenunfastenscrew[Bj
andwithdrawthePCBfromthehousingtowardtherear.
TheSERVO1 PCB1.769.310isconnectedtothechassis
viathecoolingplateofthevoltageregulators.First
detachallconnectorsleadingtothisPCB.Pushthe
draweroutcompletelyinordertogainaccesstothe
threefixingscrews.Thethreescrews[C]can
subsequentlybeunfastenedandthePCBwithdrawntoward
therear .
2 . 4 Removingtheplayermechanism.
-Removetopcover(Section2.1)
-PushdraweroutpartofthewayandsettheCDplayer
upsidedown.
-Nowpullthedrawerouttothepointwherethescrews
[Dj^becomeaccessible.
-Unfastenscrew[DjandsettheCDplayeragaininits
- . ~ normaloperatingpositiononthe fc--^ch (NOTE;holdthe
playermechanismwithyourhandtopreventitfrom
fallingoutofthe drawer).
-PulldraweroutcompletelyandcarefullylifttheCD
player.

'umrnm ¥%EMOK B225
Detachthesixconnectors(seeFig.2.5).
Theplayermechanismcannowbeliftedoutofthe
drawer»
SECTION2/2
2.5Removingthedisplay
-Openthedrawerandunfastentwoscrews [ Ej oneach
side.
-Unfastencableclamp[F]anddetachconnectorof
cableharness.Thedisplaycannowbeliftedout
bycarefullyslidingthecableharnessoutbelow
theplayermechanism.
2•6Removingthepowertransformer
-Removetopcover(seeSection2.1).
• - JJniiastenfourscrews[Gjfromthebottom.
-Detachtheconnectorsofthepowertransformerto
theSERVO1 PCB1.769.310,removepowerinletby
unfasteningthetwoscrewsandunfastenscrew[Hj
(blackcable,solderingtag).
-Thetransformercannowberemoved.
2.7Removingthedrawermotor
-Removetopcover(seeSection2.1).
-Removepowertransformer(seeSection2.6).
-Unfastenthreescrews[Hjfromthetop,unhookspring
[I], detachconnectorsleadingfromthemotorto
themicroprocessorPCB1.769.320,andcarefullylift
outthemotor.

UJPEMKiKEl/OX • . B226
2.8Removingtheoperatingpanel
-Removetopcover(Section2.1)andsidepanels
(Section2.2).
-Unfastenfourscrews[Kjeachonthetopandthe
bottomoftheoperatingpanel.
Carefullywithdrawoperatingpanel'fromthechassis
anddetachtheconnectors.
2-9Removingtheguiderods
-Removetopcover(seeSection2.1).
-Unfastentheinnerretainingring[Lj;therodcan
nowbepulledoutoftheunitfromtherear.
Note: DonotlosethesmallO-ringthatcushionsthe
drawerstop-
2.10Reassembly
TheCDplayerisreassembledbyfollowingthedismantling
stepsinthereverseorder.Itisabsolutelyessentialto
securethecableharnessinthedrawerwitha clipas
illustratedinFig.2.7.

R^OX B225 SECTION3/1
3.CIRCUITDESCRIPTIONS
3.1SERVO1 PCB 1.769.310
ThefollowingcircuitsareimplementedontheSERVO1
PCB;
-Stabilizationofthesupplyvoltages
-Drawerpositiondetector
-Focuscontrolloop
-Discmotorcontrolloop
3.1.1Stabilizationofthesupplyvoltages
Allsupplyvoltagesarestabilizedbyvoltagecontrollers
(IC4 toIC9, LM317/LM337).
The+5Vsupply(+5V STBY)isalwaysavailable.It
suppliesthemicroprocessorsystemandtheIRreceiver
evenwhentheCDplayerisswitchedoff (standby).
Theremainingsupplyvoltagesareswitchedonoroff
bythemicroprocessorwiththePS-OFFsignal.When
theCDplayerisswitchedoff,PS-OFFbecomes"H"(+5V)
andtransistorsQ9andQ10becomeconductive
(staturated), causingthe+5V and+12V supplyvoltages
todroptoa residualvoltageof1.3V.The-7V supply
isswitchedoffthroughthecircuitR38, R39? andQ8;
the-12V supplyviaR52,R54,andQll;andthe-17V
supplyviaR51, R53f andQ12.Thispreventsthepositive
supplyvoltagesfrombecomingnegative.Thevoltage
isdoubledthroughdiodesD15,D16,D17andcapacitors
C29, C30# andtakentothevoltagecontrollerIC9for
the-17V supply.D18protectsthecontrollerfrom
anexcessivedirect-axiscomponentofthevoltage.
3.1.2Drawerpositiondetector
ThetwolightbarriersDLQ1andDLQ2(onPCB 1.769.310)
checkwhetherthedrawerisopenorclosed.The
correspondingsignalsindicatethefollowingconditions:

R^OX B225 SECTION3/2
3.1.3Focuscontrolloop
Thelenscanbemovedverticallyandisdesignedsimilar
tothemechanicalsystemofa speaker.Thelensis
controlledmagnetically.Thecoilisstationaryand
themagnetmoves.ThefocuserrorsignalFOC-ERRis
firstamplified(leadamplifierIC2a,R3,R12,R16,
R17, C3,C4)andsubsequentlytakentothecontrolling
amplifier ("lag" amplifierRl,R2,R5,Rll,R15,R29,
R30, C2,C12,IC2b,Q6,Q7andtheimpedanceofthe
lens coil). InSTOPmode,thecontrolloopisinterrupted
viaQlbythesignalFOC-0{=H)whichmeansthatno
unnecessarypowerisconsumedbytheoutput-amplifier
(Q6andQl).
Thestart-upcircuit(IC1,R6,R7 ) adjuststhefocussing
tothereflectivelayerofthecompactdisc.Thesignals
FC-1andFC-2arealternatingiyswitchedto"H",causing
thelenstomovealternatingiyupordown.Oncethe
correctfocushasbeenfound,thesignalFOC-NEGbriefly
dropsto"L".Themicroprocessorthenenablesthefocus
controlloop (FOC-0, FC-1,andFC-2- "L" ).. Upto12,000
trackspersecondareskippedinfastsearchmode.
Becausethefocussinglensreadjustsforeachtrack,a
whistlingsoundofapproximately12kHzwoulddevelopas
isthecasewitha speaker.Thiswhistlingsoundis
eliminatedbyR60,R61,C31,Q13inthecontrolloop.
Thisfilterisonlyactiveinsearchmode.
3.1.4Discmotorcontrolloop
Thedatafromthecompactdiscmustbesuppliedas
steadilyaspossibletothedigitalsignalprocessing
circuit. Thespeedwithwhichthesedata(bits)arrive
dependsonthepositionofthelaserpick-up(constant
peripheralspeedbetween1.2and1.4m/s).
Ifthelaserpick-upreadsinthemiddleoftheCD,
the^speedis-muchhigherthanneartheedge.Thespeed
correctionsignalMCESisgeneratedintheerror
correctionIc"(SAA7020onPCB 1.769.300).
ThesignalMCESisswitchedofforonviathesignal
FOC-0(R15,R16,IC3bonPCB 1.769.330). Thesignal
isfirstfilteredviaa 2ndorderlowpass(R22,R23,
R25r R26,R28,C10,Cll, IC3b). The"leadnetwork"
isformedbyC9,R19,R21,R24,andR28,the,rlagnetwork"
byIC3a,C6,C7 , R8 , Q2,andQ3.
Assoonasthefocalpointhasbeenfound,thesignal
FOC-0changesto"LOW1'andthesignalMCESisenabled.
AnegativepulseviaC5issimultaneouslytriggeredon
IC3a, pin3,therebyfullydrivingtransistorQ3inorder
torapidlyacceleratethecompactdisc.Thespeedis
subsequentlycontrolledbytheMCESsignal.

WmrMM R^I/OX• B225 • SECTION 3/3
3.2MicroprocessorPCB 1.769.320
Themicroprocessorsystemandthedrawercontrolare
implementedonthemicroprocessorPCB1.769=320.
3.2.1Microprocessorsystem
Themastermicroprocessor(M-jiP,IC2 ) scansthekeyboard
(POOtoPG5,P10toP14).Themicroprocessorsystemis
resetwhentheLOADkeyispressed.Toenable
differentiationbetweena powerfailureanda LOAD
command,P15ofthemasterprocessorisalsopulledto
"LfI inconjunctionwitha LOADcommand.CapacitorC12
latchesthisconditionuntilP15isread.This
unconventionalcircuitarrangementofferstheadvantage
thata RESETcommandcanbeinitiatedatanytimeby
pressingtheLOADkeyintheeventthatthesystem
becomesblockedforanyreason.
ThecommandsfromtheIRreceiverortheREMOTEsocket
arereadthroughtheinterruptinputofthemaster
processor . Whena commandarrivesfromtheIRremote
control, theIR-RECsignalisswitchedto"LOW"for
approximatelyonesecond,causingtheLEDintheIR
receiverwindowtoturnon(commandacknowledgment).
Thesignals BRA^TOS3! andDRA-POS-Fsupplytheprocessor
withdrawerpositioninformation.
ThesignalsCLK,DATA, DLEN-1, andDLEN-2controlthe
twoLCDdriversPCE2111(onPCB 1.769.250).
Thegainoftheheadphonesamplifierandthe
VARIABLEOUTPUTiscontrolledbythesignalsCLK,DATA,
andDLEN-3(onPCB 1.769.280).
Theslavemicroprocessor(S-]iP,IC4 ) processesthe
subcode(supplementaryinformationonthecompactdisk
suchastrack,time, etc.). Therequiredsignals
originatefromPCB 1.769.300 (IC13,SAA7010,signals
Q-SYNC,SWCLK,Q-DATA,and P-BIT).
The-signalsRC-0andRC-0switchtheradial-control
looponoroff.Whentheradialcontrolloopisswitched
off(RC-0= L),thelaserpick-upcanberepositioned
withthesignalsRCl,RC2,CUR-SUM,andCUR-DIR.
Thetracksignal(TRK)isreadthroughtheinterrupt
inputoftheslaveprocessor.Thissignalchangesto
"L" assoonasthelaserpick-uppassesovera track.The
directioninwhichthelaserpick-upmovesisreported
totheslaveprocessorbythesignalTl.Thissignal
alsochangesto"L"assoonasthelaserpick-uppasses
overa track.Itisalsousedinsearchmodeforcounting
thetracks.Becausethecountingspeedofthe
microprocessorisnothighenough,onlyeveryothertrack
iscountedinfastsearchmode(divisionby2, IC6b).
AnyprogramenteredthroughthekeyboardIsstored
serially,in.IC5(serialRAM).
BothmicroprocessorsareinitializedbyIC1(resetchip
TL 7705). The+5V STBYsupplyissupervisedbyICl
viapin7.A resetisalso ' initialwaiviaRl/R8,andC8
whentheLOADkeyispressed.
Commandsfroma cable-typeremotecontrolcanberead
throughtheREMOTEsocket(pin2 andpin3).These
commandsareelectricallyisolatedthroughthe
optocoupierIC12a.Thesesignalsareconvertedto
TTLsignalsbythecomparatorcircuit(IC9a,R44,R45,
R48, andR60).Inordertodisablethecommandsfrom
theinfraredreceiver,thevoltageatpin4 mustbe
higherthanonpin2 by+5V.The+5V STBYoftheREMOTE
socketcanbeusedforthispurpose(interconnectpins1
and2,pins4 and5).TheIRsignalisthusshort-
circuitedvia DLQ2, R41,R42,R43,R62,andIC9b.

r^;-:;:^,- n^ox B225 SECTION3/4
3.2.2Drawermotorcontrol
Thedrawermotoramplifier(IClOa,R52,53,56, 57, and
R58, C14,Q8andQ9)iscontrolledthroughtheshift
registerIC3(pins4 and5).Ifthedrawermovement
isblockedduringtheopeningorclosingoperation,
themotorcurrentrisesandhencethevoltageacross
R64. SignalTlofthemasterprocessorconsequently
changes'to"L"(circuitR40,54,55,59,63, Q6,^Q7, C13,
and IClOb). Inresponsethemasterprocessorreverses
thedirectionofthedrawermovement.
3.3 SERVO-2PCB
1.769.330
TheSERVO2 PCB 1.769.330 containsthecircuitsfor
radialcontrolandtheIRreceiver.
3.3.1Radialcontrol
Amovingarmallowsthelaserpick-uptofollowthe
trackhorizontally.Thisarmbasicallyfunctionslike
amovingcoilinstrument.
Theradial-controlcircuitcanbesubdividedintofour
blocks:
-Radialcontrolcircuit
-AGCcircuit
-Offsetcontrolcircuit
-Trackdetectioncircuit
3.-3.2 Radial-controlcircuit
Thevalueoftheradial-errorsignalcanbecomputed
asfollows^RE=kd(II+12+13+14)- k (II+ 12).
Thevalueofk isdeterminedbytheAGCcircuit,and
dbytheoffsetcontrolcircuit.
RAD-ERR2=11+12
RAD-ERR1=13+14
ThesignalsRAD-ERR1andRAD-ERR2aresummedviathe
circuitIC9b,R58/59/61/62/63andQ6.Thesumflowsasa
currentthroughR63andQ6.TheerrorsignalRAD-ERR2 is
convertedviaR55andR57toa currentthatflowsthrough
R54andtransistorE ofIC8.Thefactork isformedby
transistorsA andB aswellasC andD (IC8), factord is
formedbyQ5andtransistorF (IC8).
ThesignalRAD-ERR2 x k (=k[II+ 12])onpin10ofIC9c
appearsonpin9 ofIC9c;thesignal[RAD-ERR1+
RAD-ERR2Jkd(=kd[11+ 12+ 13+ 14j)appearsonpin10
ofIC9c.Thedifferencesignal(RE),developedinIC9c,
appearsonPin8 (RE= kd[II+ 12+ 13+ 14 j - K[I1+
K2j).The"lag"networkoftheradialcontrolis
implementedbyR66,R67,R68,C15,andIC9d,the"lead"
networkbyR69,R7 0, andC16.Thesignalisconductedto
IC5throughtheprotectivediodesD5andD6.Thesignal
is^takenthroughswitchB (IC5)topin2 ofIC2which
togetherwithQ2,Q3;R6,R7",R8,RT1,andC5constitutes
the_outputstagefortheradial-controlsignalRAD-MOT+/
-RAD-MOT-. RT1protectsthe coil;- ThJBMwontrolcanbe
disabled(Signal RC-o). Thisoccursinsearch,pause,
forwardandreversemode.Thelaserpick-upcanbe
positionedduringthisphasewiththesignalsRC-1,RC-2,
CUR-DIR,andCUR-SUM.

KEI/OX
B225 SECTION3/5
3.3.3Automaticgaincontrol(AGC)circuit
Thebandwidthoftheradial-controlcircuitisstabilized
bythiscircuit.A 650Hzsine-wavesignalisgenerated
inthecircuitIClOc,IClld,C22, C23# C24,C25, R85r
R86, R87? R90,andR91.Asthegainincreasesor
decreasesthephaserelationofthesuppliedsignal
becomesalsolargerorsmallerwithrespecttothe
returningsignal*Thetwosignalsarecomparedinthe
phasedetector(ICll)anda newsignalisdeveloped.
Thelatterisproportionaltothephageandalsotothe
gain. Thissignalcontrolsthefactork.Thegainislaid,
outfora"phaseshiftbetweenthesignals-of-.135°The
650Hz.sine-wavesignalisthereforefedintothecontrol
loopatpin13ofIC9dthrougha 45°phaseshifter(R84,
C21). Thephaseshiftis90°attheinputofthephase
detector.The650Hzsine-wavesignaliseliminatedfrom
thecontrolcircuitthrougha bandpass(IClOd, R82r
R83, C19,C20)andconvertedinICllatoa square-wave
signal. Thissquare-wavesignalisinputtothephase
comparator(ICllc,pin8).Thephasereferenceis
suppliedbypin9 ofICllc.
3.3.4Offsetcontrolcircuit
Theasymmetryofthereflectedlaserbeamiscorrected
bythiscircuittoensurethatthelaserbeamiskept
exactlyonthecenterofthetrack.Thedifference
betweenminimumandmaximumreflectionisthegreatest
(presenceofpit= minimumreflection,betweenpits
=maximumreflection)whenthelaserbeamfollowsexactly
thecenterofthetrack.
Throughthe650Hzsine-wavesignalthemovingarm
oscillateswithanamplitudeof0.05jim.
Ifthelaserbeamisonthetrackcenter,allhalf-waves
ofthefilteredoutsignalarefoldedtothesame
(positive)side.Ifthelaserbeamistotherightofthe
trackcenter,thesignalisin~phasewiththe650Hz
oscillationsofthemovingarm,orantiphaseifthebeam
isontheleftofthetrackcenter.
ThevoltageacrossR63isproportionaltothereflected
lightintensity (11 + 12 + I3 + I4). Thevoltageisamplified
throughIC6a, R30f R31rand R64# andthe650Hzcomponent
isfilteredoutina bandpass(R32,R33,R34,R35,R37,
Cll, C12,and IC7b). Thefilteredsignalisinverted
throughlC7arR36,andR38.Theformerandthe
noninvertedsignalaretakentoswitchC ofIC5.The
outputofthisswitch(IC5,pin4)isintegratedthrough
IC7dandC.30anddeterminesthefactord (Q5and
transistor'F ofIC8).ThestatusofswitchC (IC5)
iscontrolledbythe650Hzsignalinthecontrolloop
.-vara-thebandpass R42f R43r R44 , R45,C13,C14 , D4,
"andIC7c.

WT^ZJ'jLTi R^OX B225 SECTION3/8
3 . 3.5Trackdetectioncircuit
Thetrackswhichareskimmedoverbythelaserpick-up
arereadthroughtheinterruptinputoftheslave
processor (TRK-SIG). Thissignalisgeneratedfromthe
signalavailableatIC6,pin1 (proportionalto
[ I1+ I2 +I3+ I4J ), theDOandtheHFLsignal.ThesignalDO
is,!L,!whennoerrorlocationisdetectedontheCD.
TheHFLsignalis"H"whentheHFsignalislargeenough.
TheTRKsignalisonly"L"whentheHEsignalistoo
small. Foreachskippedtrack,HFLis"L"ifnoerror
locationisdetectedontheCD (DO="L"). Theradial-error
signalRE(IC9c,pin8)informswhetherthelaserscanner
ispositionedtotheleftortherightofthetrack.The
signalrequiredforthispurpose(RAD-POS)isgenerated
viaIC3c,R12,R19,andR20fromtheradial-errorsignal.
3.4PreamplifierandlaserPCB1.769.100.35
Thisboardcomprisesthefollowingcircuits:
-Lasercontrol
-Signalsforfocusandradialcontrol
-HFsignalamplifier
3.4.1Lasercontrol
ThelaserdiodeissuppliedviaQ4.Theintensityof
thelaserlightcanbecheckedthroughthe"monitor
photodiode"andadjustedwiththetrimmerpotentiometer
R8CT.
ThesignalLAS-OFF(fromPCB 1.769.310 / IC1)switches
thelaseronoroff.Iftheintensityofthelaser
becomestoosmall,thecurrentflowingthroughthe
monitorphotodiodedecreasescorrespondingly.Thevoltage
acrossR84alsodrops.Theoutputof.opampIC3a
consequentlybecomesmorepositiveandQ4more
conductive.Theintensityofthelaserisadjustedby
dischargingsomeofthecurrentthroughthemonitor
photodiodeviaR80andR81.
3.4.2Focusandradial-controlsignals
Thefollowingsignalsaregeneratedbythiscircuit;
-FOC-ERR
-RAD-ERR1
-RAD-ERR2
Thecurrentsofthefourphotodiodes(AltoA4)are
amplifiedinIC1.Thecorrespondingerrorsignalsare
developedbythesubsequentnetwork.Thefocuserror
signalisproportionalto(11+14)- (12+13). 13+ 14
constitutesthe•RAD-ERRlsignal,II+ 12theRAD-ERR2
signal. Thegainofthefocuscontrolloopcanbe
-^djiis/tedwithR58,thebalancewithR41(notincludedin
'all versions).
"'3-4.3HFsignalamplifier
ThecircuitcomprisingtransistorsQlthroughQl consti-
tutesthesignalamplifierwithbandpasscharacteristic.
Low-frequency(e.g.controlsignalsoftheservos)
andhigh-frequency disturbancesignalsareconsequently
filteredout.
3.5DecoderPCB 1.769.300
ThedecoderPCBcontainsthefollowingcircuits:
-Digitalsignalprocessing
-Digitalsine-wavegenerator
-HF£andDOdetector

mnruiDjiMM HEMOX B225SECTION3/7
3.5.1Digitalsignalprocessing
TheHFsignalisconvertedinIC13(SAA7010}into
diqitalsiqnalsandsplitintoaudioandinformation
data(subcode,fortheslave processor). TheCLOCK
signalisalsoregeneratedinJC13.Theaudiodata
arebroughtintothecorrecttimeslotpattern.Corrupted
audiodataarenotrecognizedin1C12andcorrected
ifnecessary.Shouldtheerrorsbeincorrigible,the
missingsamplevaluesarereplacedin.IC10(SAA7000)
throughinterpolation.Shouldthisalsobeinfeasible,
theHFsignalisslowlymuted(soft muting). Thespeed
oftheCDmotoriscontrolledbythesignalMCES(IC1,
pin 4 ) .
3.5.2Digitalsine-wavegenerator
ThePROM(IC4)containsa valuetableforthesine-wave
signalwhichrepresentsthemaximumpossiblelevel
ofa CD.
ThecircuitconsistsofIC5throughIC9withIC5and
IC6supplyingtheaddressesforthePROM.Parallel/serial
dataconversionisperformedinIC3.Thechange-over
betweenaudiodatafromtheCDandthe1 kHzsine-wave
signaliscontrolledbyIC1.
3•5•3HFLandDOdetector
TheHFsignalisfedintotheinvertingdifferential
amplifierQlandQ2throughC6andR2.Theoutputsignals
areDC-decoupledviaC8andC9respectivelyandtied
toDCgroundviaD2andD3.D4andD5orD6andD7
respectivelyconstitutea full-waverectifiereach
throughwhichthecapacitorsC10orCllarecharged.
Witha normalHFsignaltheDOsignalis"LSiandthe
HFLsignalis"H".IftheHFsignaldropstoapproxi-
mately70%ofthenormalvalue,theHFLsignalalso
changesto
!,Lt!
. OnlywhentheHFsignaldropsto
approximately10%of - thenormalvaluedoestheDOsignal
changeto"H".
TopreventtheoutputsignalsofIC11frombeing
influencedtoostronglybyminorcontaminations(e.g.
fingerprints)ontheCD, transistorQ3hasbeenaddedto
theoutput.WhentheRFlevelisatnominalvalue,pin7
ofIC11is "Hl! . Q3becomesconductiveandthecircuit
withCllreceivesa smallertimeconstant.Withlevel
fluctuationscausedbyminorcontaminations,thelevels
ofthetwoinputcapacitorsfluctuateinparallel,but
neithertheDOnortheHFLsignalareaffected.
3.6DACPCS 1.769.280 .
Tfee" following'circuitsareimplementedonthisPCB:
-Digitalfiltering(oversampling)anddigital/analog
-•conversion
-Leveladjustmentandheadphones"aTifffiifier
3.6.1Digitalfiltering(oversampling)andD/Aconversion
IC1(SAA7030)containstwoidenticalfiltersforboth
channels.Thesefiltersfeature3 sections:
~Oversamplingsection
-Transversaldigitalfilter
-Noiseshaper
Aftereachscanningcycle,thenewsamplevaluesare
insertedbyinterpolationintothe16-bitinformation
arrivingfromthedecoder.Thescanningratethusbecomes
4timesgreater(4x 44.1kHz= 176.4kHz).Thespectral
linesabove20kHzupto176.4kHz- 20kHzarefiltered
outbythetransversalfilter.Thesamplevaluesare
truncatedto14 bits. Thenoiseshapersubsequently
delaysthetruncationerrorbythescandurationand
negativelyaddedtothenextsamplevalue.The
guantisizingnoisecausedbytruncationisthereby
largelyshiftedtowardthefrequencyrangeabove20kHz.
ThedigitalsignalisconvertedinIC101orIC201
(TDA1540)toananalogsignal.Inordertofilterout
theresidualfrequencycomponentatn (176.4kHz
+;20kHz),a lowpassofthethirdorder(Besselfilter)
hasbeenaddedtotheconverteroutput.

r'r:;T*5^ R^QX
B225 SECTION3/8*
Thepreemphasisiscorrectedwiththecircuitillustratec
inFig.3.13.ThesubcodeontheCDspecifieswhether
theselectionwasrecordedwithorwithoutpreemphasis.
Thecharacteristicofthecorrespondingfiltercan
beadjustedwiththePREEMsignal.
3.6.2Leveladjustmentandheadphonesamplifier
Thevolumeiscontrolledbya DUALD/Aconverter
(AD7528). Itservesasanattenuatorbeforethe
correspondinginput(IC103a,pin2 = left-handchannel
/IC203bfpin6 = right-hand channel). Thenegative-
feedbackresistancesofbothopampsremainunchanged
whichmeansthatthelevelcanonlybeattenuatedwith
thiscircuit.ThedualD/Aconverteriscontrolledbya
CMOSshiftregisterthroughthesignalsDLEN-3,DATA,and
CLK.ThecircuitillustratedinFig.3.14constitutesthe
outputamplifierfortheheadphonessocketandalso
theVARIABLEOUTPUT*Thesignalisalsoattenuatedfor
thispurposethrougha voltagedividersothatthesignal
isthesame(2V RMS)atbothoutputs(FIXEDand
VARIABLE). ThesignalistakenthroughrelayKlinorder
topreventpower-onswitchingclicks.Whenpoweris
applied.,therelayisselectedbythe
KILLsignal(whichrisesto+5V afterapproximately
1to2 seconds). Asa result,theoutputsareonly
through-connectedwhenthesupplyvoltagesarestable.

REI/OX
B225 SECTION4/1
4. TESTPOINTS,ADJUSTMENTSON B2 2 5
4
m
i TestpointsonB225
4.1.1TestpointsonSERVO1 PCB1.769.310

'lDj[j R^OX B225 SECTION4/2
IfnoCOismountedwhenPLAYisselected*thesignalsonTP26
an CJ 2 7 become^l?Vinfourintervalsofapproximatelyonesecond
each• "
(*)InPLAY-mode*thesignalpatternofthesetestpointsdepends
onthewobbleofthemountedcompactdisc*

w^rumi
R^OX B225 SECTION4/3
4.1.2TestpointsonSERVO2 PCB1.769.330

hFtEMOX B225 SECTION
4/4
whensignals are receivedfroni theIR- remotecontrol t pulses of
•4.3Voccur on TP52«
4.13TestpointsonMICmPRGCESSQRPCB1.769.320,