Arcam ALPHA ONE User manual

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ARCAM
ALPHA 5 CD PLAYER
SERVICE MANUAL

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ALPHA 5 CD SERVICE MANUAL
ALPHA 5 CD PLAYER SERVICE MANUAL
Issue 1 Serial No. 30000
Paul Newton/Andy Howe August '93
Arcam Drawing No. H04/0022
CONTENTS
CIRCUIT DESCRIPTION
AudioBoard ........................................................................................................ 2
Mono Board ..................................................................................................... 2
Photodiodesignal&RadialErrorProcessors.........................................................................2
Microcontroller & Decoder .............................................................................................2
Display& Keyboard .......................................................................................................4
MuteCircuit .......................................................................................................................4
Power Supply ................................................................................................................5
DISASSEMBLY FOR SERVICING .................................................................. 6
CHANGE OF MAINS VOLTAGE .................................................................... 7
LIST OF DIAGRAMS ....................................................................................... 7

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ALPHA 5 CD SERVICE MANUAL
CIRCUIT
DESCRIPTI
ON Audio
Board
Theaudioboardcontainsthedigitalfilter,DAC,audiooutput stages and associated power supplies.
The required signals from the main board are passed to the audio board via the 18 way
connector. This connector carries DAAB, CLAB, WSAB, DEEM, OV, ATSB XSYS, EFAB and +5V
line.
The DAC requires 3 supply rails to function, +5V, -5V and -15V and also a series of averaging
capacitors, (C1-7,C101-107), for the bit switches in each channel of the DAC for good linearity
and low distortion. The +5V supply is filtered by RC network R216, C219, C220 and the -15V
supply L201 and C224, C225. The output of the DAC is fed to Z1 to convert the output current
to a voltage and provide gain. The second ic, Z2, with its associatedcomponents forms a lowpass
2polefilter,which combined with the first stage formsa3 poleBesselfilter.
TransistorQ1isusedtoswitchinadditionalcomponentsif thede-emphasisflagDEEMgoes high.This is
doneautomaticallywhen adiscrecordedwithpre-emphasis isplayed.
Thedigitaloutput(DOBM)isderivedfrompin14ofthedigitalfilter (Z206) and is formed by isolating
transformerT201and associated circuitry.
The"Kill"linetomutetheaudiooutputs,withtransistorsQ2, 102, comes in on the 4th pin ofsocket
SK202whichalso carriesthedcsupplies fortheaudio board.
The audio board is supplied with smoothed +/- 25v D.C via a 4 way connector, SK202.
R201,C205andR202,C206providesadditionalfilteringbeforetheregulators.Thereare4regulators, +/-
15V and +/- 5V formed by adjustable regulators Z201,202 and Z203,204 respectively.
MonoBoard
Photodiodesignal&RadialErrorProcessors
The TDA8808(Z501) and TDA8809(Z502) ic's are the signal processors for the laser unit. The TDA8808
amplifies the photo-diode signals from the CDM-9 mechanism and processes the error signals for the
focus and radial control network. The TDA8809 provides control signals for the radial motor. These
signals are generatedfrom radial error signals received from the TDA8808 andvelocity control signals
from the control processor. Z503,(TCA0372) is a high power op-amp to drive the radial arm. Z604 is
usedtodrivethe turntable motor with the use of thetransistoroutputstageformed byQ604andQ605.
Unlikeearliermechanisms theCDM-9mechanism is aligned during manufacture and is not
adjustable.
Microcontroller& Decoder
The appropriate signals are passed to and from these ic's to the servo microprocessor, 68HC05C8,
(Z603)andthedecoder(Z601)ic.Theoutputfromthe decoderchipgoesvia an 18 way connector to
the audio board.
The meaningof theused signals on the servo microprocessoris as
follows: 2

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ALPHA 5 CD SERVICE MANUAL
Si/RD:On/off control for the focus servo system. This line is continuously made low by the SERVO-uP during
the stop condition. At starting up, the SERVO-uP forces this line in a high-Z state. In this case the focus servo
system is enabled. After some time the Si/RD-signal is made low for a short period to indicate that the focus
servo is ready.
TL: Trackloss.ThissignalismadelowbytheTDA8808assoonasatrackislost.
REdig: Digitalradialerrorsignal(Re2- RE1).
BO:
B1: Inputcontrolbitsforoff-,catch-,play-statusand
B2: DAC-output-current for radial motor. B3:
RE:
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/2 bit DAC. This signal is normally held high-Z bythe SERVOuP.However when TLgoes low the REline
can influence the proportionalamplificationoftheradialservo(improvedS-curve).
CRI: Counterresetinhibit.Thissignalgoeslowduringarealtrackloss(>600us)or during execution of a jump
command. When low, this signal allows the divide-by-588mastercounterintheDEMODtimingoftheSAA7310
torunfree.Thesignalbecomeshighduringinitializationofthe"catch"statusoftheradialservo.
DODS: Drop-out detector suppression. This signal is externally hard wired with the CRI-
signal.
QRA:
QDA: Subcode channel.
QCL:
SWAB/SSM:Subcoding word clock and start/stop turntable motor. This line is continuously made low by the
SERVO-uP during the stop condition. At starting up the SERVO-uP forces thisline tothehigh-Zstate.In thiscase
theturntablemotoris started and the subcoding word clock is connected to this line by the SAA731 0. If this
line is forced low by the SERVO-uP, a motor stop condition will be decoded by the SAA7310 and fed to the
turntable motor control logic circuit.
MC: Motorspeedcontrol.TheSERVO-uPusesthislinetomeasuretheturntablemotor starting up time. This is
necessary for the 8cm/12cm disk identification andfor thesoftware controlledbrake of theturntable motor.
TEMP: Motor offset and bandwidth switch. At starting up the turntable motor, the SERVO-uP measures the
starting up time (cfr. MCES). If this time is small (small moment of inertia), the TTMO line it turned high by
the SERVO-uP. Ifthis time is long (high moment of inertia), the TTMO line remains low. As theTTMO line is
switched high the DC amplification is lowered and an offset is injectedtothe turntablemotor circuit.
ALPHA 5 CD SERVICE MANUAL
PowerSupply
Themainsinputtotheunitmaybe230Vor115V,selectableby insertion of the appropriate fuse.
This unit does not have a mains on-off power switch. Instead there is a 'Standby' switch (SW402)
which turns off the power to some parts of the circuit (decoder, digital filter and display)andputs the
mainmicrocontrollerintoaresetcondition.
Two separate windings on the secondary provide isolated digital and analogue power supplies.
The digital supplies consist of +10V & -10V unregulated to power the servo drivers and motors and
+5V (Z402) and -5V(Z403)forthe critical signal processing and microcontrollers.Twoothertaps onthe

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samewindingareregulated by Z401, providing the - 20Vrailrequired bythefluorescentdisplay.
There is an additional winding that powers the filament on the display via pass transistor Q403.
Pressingthe frontpanel'Display' button toggles flip-flopZ405,switchingQ403 (and therefore the display) on
and off.
Thesupplytotheaudioboard is+25V,-25Vwithan analogueground.
DISASSEMBLYFORSERVICING
ANTISTATICPRECAUTIONS MUSTBEOBSERVED
1. Removethecoverbyremovingthe4 sidescrews and4 rear screws.Slide the cover backwards and
up.
2. Removethe4sidescrewsholdingthefrontpanelonandone screw from the centre of thefrontpanel
accessedfrom inside theunit.Thefrontshouldnowpulloff.
3. Removethe2 screwsfromthedigitalandaudiooutputsocketson the audio board.
Squeezethepcbpillarin thecentreoftheaudioboardand pull the board up. It will
be tightbecauseoftheconnectorsbetween theaudioand monoboards.
NOTE:Becausethemasterclockisontheaudioboardtheunit will not function with the
audio boardremovedfromtheplayer.
4. PushthetrayoftheCDplayerforwardtorevealamountingscrew at the rear of the mechanism
chassis. Remove this screw.
5. Remove4screws situatedon themonoboard close to the corners of the
transformer.
6. Remove the 2screws connecting the rear panel to the mains inlet socket and squeezethetopof
the2pcbpillars.
Themonoboard,complete withmechanism,subfrontanddisplay board should now be
free and can be pulled up and out of the chassis.
The display board can be removed, if necessary, byremovingthe2screwson the
front and squeezing the pcb pillars. The board can then be pulled off its 2
connectors.
The mechanism can be removed by removing 2 screws from the sub front and
2 screws from the underside of the monoboard. Unclip the 3 connectors from the
mechanism to monoboard.
Lift the mechanism up carefully and release the flexible pcb from the mechanism to
monoboard. The mechanism can now be removed fully.
NOTE:-Youmustfitapaperclipacrosstheendoftheflexiblepcb topreventstatic
damagetothelaserwhilstitisoutofthecase.

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ALPHA 5 CD SERVICE MANUAL
CHANGEOFMAINSVOLTAGE
WARNING - the unit must be unplugged from the mains when replacing the fuse as the mains inlet
and fuse are at mains potential even with the unit switched off.
The Alpha 5 can be set for use on 230v or 115v mains supplies.
There are 2 mains fuseholders in the unit - one marked 230v & the other 115v
and the fuseholder with the fuse fitted to it determines the working voltage. To
change voltage remove the fitted fuse and fit the correct fuse to the other
fuseholder.
The correct fuses are:
160mA antisurge for 230v
25OmA antisurge for 11 5v
DIAGRAMS
ALPHA 5BLOCKDIAGRAM
SERVICE MODE BLOCK
DIAGRAM
FAULT FINDING CHART
MONO BOARD:POWER
SUPPLIES
MONOBOARD:PHOTODIODE&
RADIALERROR PROCESSORS
MONO BOARD: SERVOuP&
DECODER
AUDIO BOARD

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DISPLAY BOARD

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