Revox B225 Service Manual

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REI/QX

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B225

IiILI„OF_CgNTEyTS page

1. GENERAL

1-1 Index of CO olayer controls 1/i
1*1* 1 General controls 1/1
1*1*2 Special controls 1/2
1*1*3 Rear panel connectors 1/3

2. t REMOVAL OF ASSEHBLIES

2.1 Removing the top cover 2/1
2*2 Removing tne side panels 2/1

2.3 Removing the individual circuit boards 2/1
2*4 Removing the player mechanism 2/1
2®5 Removing the display 2/2
2*6 Removing the po^er
2*7 Removing the drawer motor 2/1
2*8 Removing tne operating panel 2/3
Z«9 Removing the guide rods 2/3

t r

ansf or mator 2/2

3* CIRCUIT DESCRIPTIONS

3.1 SERVO 1 PC3 1.759.310 3/1

3.1®1 Stabilization of the supply voltages 3/1
3*1*2

Orawer position detector 3/1
3*1.3 Focus control loop 3/2
3*1*4

Oisc motor control loop 3/2

3.2 Microprocessor PC3 . 1.769.320 3/3

3.2*1 Microprocessor system 3/3
3^2*2

Drawer motor control 3/4
3*3 SERVO- 2 PCP 1.769*330 3/4

3.3^1 Radial control 3/4
3*3.2

Radial control circuit 3/4
3*3*3

Automatic gain control- {AGC-} circuit 3/5
3«3r-4 Offset control circuit. 3/5

3.3.5 Track detecting circuit 3/6
3*4 Preamplifier and laser PCB 1*769*100*35 3/6

3.4.1 Laser control 3/6
3*4^2

Focus and radial control signals 3/6

3«4*3 HF signal amplifier 3/6

3.5 Decoder PCh l-7o^.300 3/6
3*

t>

• 1 Digital signal processing

3»5«2 Digital sine-wave generator 3/7

3.

5. J

HFL and 0-J detector 3/7

3*o OAC TC3 1.769.23 3 3/7

3.t».l

digital filtering (oversampl ing) and 0/A conversion 3/7

3*6.2

Level adjustment and headphones amplifier 3/3

3/7

mmmm

*• TEST POINTSt ADJUSTMENTS OH E225

4 i Test points on 622^ 4/1
4«-l»l Test points on SERVO I PCB 1«?69*310 4/1

4.1.2 Test points on SERVO 2 PCB 1.769.330 4/3

4.1.3 Test points on microprocessor PCB 1.769*320 4/4

4.1.4 Test points on decoder PCB 1.769.300 4/6

4.1.5 Test points on 0AC- PCB 1.769.260 4/8
4®2 Adjustments on CO player B225 4/9

4.2.1 Aids 4/9

4.2.2 Aligning the player mechanism? general 4/9
4*2®3

4.2.4 Adjusting the balance 4/9
4«Z*5 Adjusting the focus gain 4/10
4*2*6
4*»2#7

4.3 Measuring the audi.o data 4/11
4*3.1

A i 4s

4*3#2

4.3.3 Output level 4/11

4.3*4

4.3.5 Cross talk 4/12

4.3.6 Signal-to-noise ratio* linear 4/12

4.3.7 Signal-to-noise ratio? weighted - ' 4/12

4.3.3 Phase linearity 4/12

4.4 Listening test with reference CO 4/12

eel/ox

Adjusting the laser current 4/9

Checking the -tingle alignment 4/10
Adjusting the DC component of the focus signal 4/11

Harmonic distortion 4/11

Frequency response 4/11

B225

4/i1

5* DIAGRAMS

6. SPARE PARTS

7*

TECHNICAL APPENDIX

7.1 Technical data 7/1
7«Z

Dimensions 7/2"

R^/ax

B225

1.

1.1

1.1.1

1 Ij POWER *

[

2 j

LOAD

[

3 J

STOP *

[

4 J

PLAY/NEXT

H5"f REPEAT

[6j (CD drive)

[7j (Display)

[8j (keys 0-9)

GENERAL

Index of CD player controls

General controls

Key for switching the CD player ON and
OFF.

However, certain assemblies (such
as the IR receiver) remain always switched"
on (in so-called standby
The drawer with the player mechanism

[6j opens or closes when this key is
pressed.
Interrupts the player function. The
optical laser head is retracted to the
starting position and the program is
cancelled if the CD player was in program

mode.

The position in which the laser
pickup was operating before STOP was
pressed cannot be reproduced. If this

is desired, please refer to tJL (PAUSE)

key.

Play key with the following functions;
If pressed after LOAD [2j, the CD starts
to rotate, the content list is read, and
the disc is played starting at the first
selection

(TRACK) is accessed when this key is

pressed again.

If pressed after PROGRAM MODE [26 J has
been selected: play program mode is
activated.
The selection currf.r^ly being played
is repeated immediately when this key
is pressed. If the CD player is in STOP

mode,
disc will be played. If the CD player is
in program mode, the current program step
will be repeated.
Drawer module with CD player mechanism
and liquid-crystal display. The drawer
can be opened or closed with LOAD [2].
Multifunction LC display 'which provides
information on all operating modes of
the CD player and the content of the
loaded compact disc.
Digit keys for direct addressing of
a selection (TRACK) in conjunction with
PLAY/NEXT [4j, or for programming.

(TRACK).

the first selection of the compact

The next selection

mode).

The CD player can be switched on by pressing any of
the controls [ Ij through [8j of the upper row (except
REPEAT [5j and the digit key 0). The CD player starts
in the selected operating mode.

mruim

REVOX

B225

1.1.2

The controls
roughly divided into
for supplementary player functions,
controls.

A Controls

[9] PHONES

[10] VOLUME

[11j VOLUME

[12]

CAL

13] AUTOSTOP

[ 14j

Key •

[ 15 J

VA

[16]

« key

[17] DISPLAY

Special controls

in the

+

-

TONE

*

(pause ) *

lower front-panel section

two

for

Headphones jaGk socket
200
Increases
and
Decreases
and
This calibration button connects
1000

outputs

of a connected tape deck
accurately adjusted.
CAL TONE corresponds
output level. This maximum level
is system-dependent
be exceeded even
pulses.

Interrupts

at

or program step.

is automatically positioned
the beginning
The next selection
immediately when PAUSE

pressed. Upon conclusion

selection,
again
Repositions
location toward
Interrupts

at

Repositions
location toward
Switches over
The time elapsed since

of

in normal PLAY mode.

play time from
current selection
by pressing this

function groups: controls

supplementary player functions

to 600

the

the

Hz

the end of the

any

the

ohms.

the

level

level

calibration tone

so

to

time.

current selection

headphones level

of the

the

headphones level

of the

that

the

of the

the CD

PAUSE mode.

the

the

the

the

can be

and

programming

for

headphones

VARIABLE OUTPUT.

VARIABLE OUTPUT

the

by

playing sequence

current selection

The

is

player switches

pickup from

the end.

playing sequence

pickup from

the

display mode.

the

start

can be

key.

to the

recording level

can be
The 1000 Hz
to the

and

short peak

laser pickup

next selection.

started

start.

The

maximum

will

not

at

TA [15] is

of

this

any

any

the

start

is

displayed

total

to the

displayed

a

These functions

PROGRAMMING keys

18] LOOP

19]

[20]

[21]

[ 22] STORE

[ 23] MARK

[24] TRACK/TIME

+

-

IR

*

SENSOR

can

also

be

programmed.

Command key for repeating the CD
or the proqr^4«until STOP [3j is
pressed.
Forward "paging" in program mode.
Particularly useful for modifying
an existing program.

Same function as [19] but backward
paging.
Infrared receiver window
Memory load key to be pressed after
each program step entry. The next
program step is subsequently
displayed so that the corresponding
entries can be made.
Allows a start and a stop mark
to be set in programming mode while
a selection is being played. Any
CD location can thus be programmed.
Switches the display in programming
mode from selection (track) input
to time input (minutes and

seconds).

mWU\n)MPd

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B225

[25j CURSOR

[26 J

PROGRAM

Any position on the display can
be edited by approaching it with the
cursor.
TIME mode, the cursor must be
advanced with this key in order to
enter the seconds after the minutes.
Sets the program entry mode. If
PLAY/NEXT [4J is pressed after
the program entries have been
completed, the CD player starts in
PROGRAM mode,
If the CD player is to be started

in normal mode after the program
entries have been completed, press
the PROGRAM key

PLAY/NEXT [4].

NOTE; if the display is in

[ 26 J

again before

1.1.3 Rear-panel connectors

[30] AUDIO OUTPUT FIXED. Output for connecting

[31] AUDIO OUTPUT VARIABLE. Active speakers or

[32] AC POWER. Power inlet (the setting of the

..[33J

• "

an amplifier on which the input can be matched
to the level of the CD player (the REVOX B251
amplifier is ideally matched at the

an output stagef etc. can be connected directly
to this output. The volume can be adjusted
with VOLUME + and - on the front panel of
the CD player.

line voltage selector can be checked adjacent
to it ) .

REMOTE. This connector can be used for: a)

disabling the IR receiver and b) connecting
a cable-type remote control device.

factory).

B^OX

B225

2 . REMOVAL OF ASSEMBLIES
Important:

Disconnect the CD player from the AC supply before

removing any parts of the housing.. For certain work

it is necessary to open or close the drawer module.

This can be done manually without damaging the unit.

2.1 Removing the top cover

- Unfasten five screws [Aj on the rear of the CD player.

- Withdraw cover toward the rear.

2.2 Removing the side panels

- Unfasten two screws on each side panel in order to
remove them.

2

. 3

Removing the individual circuit boards

SECTION 2/1

The circuit boards are accessible when the top cover
is removed (Section 2.1).

The circuit boards 1.769.280 (DAC PCB), 1.769.300

(DECODER PCB), and 1.769.330 (SERVO 2 PCB) can be pulled

out of the interconnection board after the fixing screws

[ B] have been unfastened.

Four connectors must be detached before the PCB 1.769.320

(MICROPROCESSOR) is removed. Then unfasten screw [Bj

and withdraw the PCB from the housing toward the rear.
The SERVO 1 PCB 1.769.310 is connected to the chassis

via the cooling plate of the voltage regulators. First
detach all connectors leading to this PCB. Push the
drawer out completely in order to gain access to the
three fixing screws. The three screws [C] can
subsequently be unfastened and the PCB withdrawn toward
the rear

2

. 4

.

Removing the player mechanism.

- Remove top cover (Section 2.1)

- Push drawer out part of the way and set the CD player
upside down.

- Now pull the drawer out to the point where the screws
[ Dj ^become accessible.

- Unfasten screw [Dj and set the CD player again in its

- . ~ normal operating position on the

fc--^ch

(NOTE; hold the

player mechanism with your hand to prevent it from

falling out of the

drawer).

- Pull drawer out completely and carefully lift the CD
player.

'umrnm ¥%EMOK

Detach the six connectors (see Fig. 2.5).
The player mechanism can now be lifted out of the

drawer»

2.5 Removing the display

B225

SECTION 2/2

- Open the drawer and unfasten two screws [ Ej

on each

side.

- Unfasten cable clamp [F] and detach connector of
cable harness. The display can now be lifted out

by carefully sliding the cable harness out below
the player mechanism.

2 •6

Removing the power transformer

- Remove top cover (see Section 2.1).

•

- JJniiasten four screws [Gj from the bottom.

- Detach the connectors of the power transformer to

the SERVO 1 PCB 1.769.310, remove power inlet by
unfastening the two screws and unfasten screw [Hj

(black cable, soldering tag).

- The transformer can now be removed.

2.7 Removing the drawer motor

- Remove top cover (see Section 2.1).

- Remove power transformer (see Section 2.6).

- Unfasten three screws [Hj from the top, unhook spring

[I],

detach connectors leading from the motor to

the microprocessor PCB 1.769.320, and carefully lift

out the motor.

UJPEMKi KEl/OX

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B226

2.8 Removing the operating panel

- Remove top cover (Section 2.1) and side panels
(Section 2.2).

- Unfasten four screws [Kj each on the top and the

bottom of the operating panel.

Carefully withdraw operating panel' from the chassis
and detach the connectors.

2 -9

Removing the guide rods

- Remove top cover (see Section 2.1).

- Unfasten the inner retaining ring [Lj; the rod can
now be pulled out of the unit from the rear.

Note:

Do not lose the small O-ring that cushions the

drawer stop-

2.10 Reassembly

The CD player is reassembled by following the dismantling
steps in the reverse order. It is absolutely essential to
secure the cable harness in the drawer with a clip as
illustrated in Fig. 2.7.

R^OX

3. CIRCUIT DESCRIPTIONS

B225

SECTION 3/1

3.1 SERVO 1 PCB

The following circuits are implemented on the SERVO 1
PCB;

- Stabilization of the supply voltages

- Drawer position detector

- Focus control loop

- Disc motor control loop

3.1.1 Stabilization of the supply voltages

All supply voltages are stabilized by voltage controllers

(IC 4 to IC 9,
The +5V supply (+5 V STBY) is always available. It
supplies the microprocessor system and the IR receiver
even when the CD player is switched off
The remaining supply voltages are switched on or off
by the microprocessor with the PS-OFF signal. When
the CD player is switched off, PS-OFF becomes "H" (+5 V)
and transistors Q9 and Q10 become conductive

(staturated),

to drop to a residual voltage of 1.3 V. The -7 V supply

is switched off through the circuit R38,

the -12 V supply via R52, R54, and Qll; and the -17 V

supply via R51,

supply voltages from becoming negative. The voltage

is doubled through diodes D15, D16, D17 and capacitors

C29,

C30# and taken to the voltage controller IC9 for
the -17 V supply. D18 protects the controller from
an excessive direct-axis component of the voltage.

1.769.310

LM317/LM337).

(standby).

causing the +5 V and +12 V supply voltages

R39? and Q8;

R53f and Q12. This prevents the positive

3.1.2 Drawer position detector

The two light barriers DLQ1 and DLQ2 (on PCB

1.769.310)
check whether the drawer is open or closed. The
corresponding signals indicate the following conditions:

R^OX

B225

3.1.3 Focus control loop

The lens can be moved vertically and is designed similar
to the mechanical system of a speaker. The lens is
controlled magnetically. The coil is stationary and
the magnet moves. The focus error signal FOC-ERR is
first amplified (lead amplifier IC2a, R3, R12, R16,

R17,

C3, C4) and subsequently taken to the controlling
amplifier
R30,
lens

("lag"

amplifier Rl, R2, R5, Rll, R15, R29,

C2, C12, IC2b, Q6, Q7 and the impedance of the

coil).

In STOP mode, the control loop is interrupted
via Ql by the signal FOC-0 {= H) which means that no
unnecessary power is consumed by the output-amplifier

(Q6 and Ql).

SECTION 3/2

The start-up circuit (IC1, R6, R7 ) adjusts the focussing
to the reflective layer of the compact disc. The signals
FC-1 and FC-2 are alternatingiy switched to "H", causing
the lens to move alternatingiy up or down. Once the
correct focus has been found, the signal FOC-NEG briefly
drops to "L". The microprocessor then enables the focus
control loop

(FOC-0,

FC-1, and FC-2 -

"L"

)..

Up to 12,000
tracks per second are skipped in fast search mode.
Because the focussing lens readjusts for each track, a
whistling sound of approximately 12 kHz would develop as
is the case with a speaker. This whistling sound is

eliminated by R60, R61, C31, Q13 in the control loop.
This filter is only active in search mode.

3.1.4 Disc motor control loop

The data from the compact disc must be supplied as

steadily as possible to the digital signal processing

circuit.
depends on the position of the laser pick-up (constant
peripheral speed between 1.2 and 1.4 m/s).

If the laser pick-up reads in the middle of the CD,

the^speed is-much higher than near the edge. The speed
correction signal MCES is generated in the error
correction Ic"(SAA 7020 on PCB

The signal MCES is switched off or on via the signal
FOC-0 (R15, R16, IC3b on PCB
is first filtered via a 2nd order low pass (R22, R23,

R25r R26, R28, C10, Cll,

is formed by C9,R19, R21, R24, and R28, the

by IC3a, C6, C7 , R8 , Q2, and Q3.
As soon as the focal point has been found, the signal
FOC-0 changes to "LOW1' and the signal MCES is enabled.
A negative pulse via C5 is simultaneously triggered on
IC3a,
to rapidly accelerate the compact disc. The speed is
subsequently controlled by the MCES signal.

The speed with which these data (bits) arrive

1.769.300).

1.769.330).

IC3b).

pin 3, thereby fully driving transistor Q3 in order

The "lead network"

The signal

,r

lag network"

WmrMM R^I/OX •

B225

•

SECTION

3/3

3.2 Microprocessor PCB

The microprocessor system and the drawer control are

implemented on the microprocessor PCB 1.769=320.

3.2.1 Microprocessor system

The master microprocessor (M-jiP, IC2 ) scans the keyboard

(POO to PG5, P10 to P14). The microprocessor system is
reset when the LOAD key is pressed. To enable
differentiation between a power failure and a LOAD
command, P15 of the master processor is also pulled to

"LfI in conjunction with a LOAD command. Capacitor C12
latches this condition until P15 is read. This

unconventional circuit arrangement offers the advantage
that a RESET command can be initiated at any time by
pressing the LOAD key in the event that the system
becomes blocked for any reason.

The commands from the IR receiver or the REMOTE socket

are read through the interrupt input of the master
processor . When a command arrives from the IR remote
control,
approximately one second, causing the LED in the IR
receiver window to turn on (command acknowledgment).
The signals
with drawer position information.
The signals CLK, DATA,
two LCD drivers PCE 2111 (on PCB
The gain of the headphones amplifier and the
VARIABLE OUTPUT is controlled by the signals CLK, DATA,
and DLEN-3 (on PCB

The slave microprocessor (S-]iP, IC4 ) processes the
subcode (supplementary information on the compact disk
such as track, time,
originate from PCB
Q-SYNC, SWCLK, Q-DATA, and
The-signals RC-0 and RC-0 switch the radial-control

loop on or off. When the radial control loop is switched
off (RC-0 = L), the laser pick-up can be repositioned
with the signals RCl, RC2, CUR-SUM, and CUR-DIR.

The track signal (TRK) is read through the interrupt

input of the slave processor. This signal changes to

"L"

direction in which the laser pick-up moves is reported
to the slave processor by the signal Tl. This signal

also changes to "L" as soon as the laser pick-up passes
over a track. It is also used in search mode for counting
the tracks. Because the counting speed of the
microprocessor is not high enough, only every other track

is counted in fast search mode (division by 2,
Any program entered through the keyboard Is stored
serially ,in.IC5 (serial RAM).

Both microprocessors are initialized by IC1 (reset chip
TL

7705).
via pin 7. A reset is also ' initialwai via Rl/ R8, and C8
when the LOAD key is pressed.
Commands from a cable-type remote control can be read
through the REMOTE socket (pin 2 and pin 3). These
commands are electrically isolated through the
optocoupier IC 12a. These signals are converted to
TTL signals by the comparator circuit (IC9a, R44, R45,
R48,
the infrared receiver, the voltage at pin 4 must be
higher than on pin 2 by +5 V. The +5 V STBY of the REMOTE
socket can be used for this purpose (interconnect pins 1
and 2, pins 4 and 5). The IR signal is thus short-

circuited via

the IR-REC signal is switched to "LOW" for

BRA^TOS3!

as soon as the laser pick-up passes over a track. The

The +5 V STBY supply is supervised by ICl

and R60). In order to disable the commands from

DLQ2,

1.769.320

and DRA-POS-F supply the processor

DLEN-1,

1.769.280).

etc.).

1.769.300

R41, R42, R43, R62, and IC9b.

and DLEN-2 control the

1.769.250).

The required signals

(IC13, SAA 7010, signals

P-BIT).

IC6b).

57,

B225

and

C13,

r^;-:;:^,-

3.2.2 Drawer motor control
The drawer motor amplifier (IClOa, R52,53,56,

R58,

C14, Q8 and Q9) is controlled through the shift
register IC3 (pins 4 and 5). If the drawer movement
is blocked during the opening or closing operation,
the motor current rises and hence the voltage across
R64.

Signal Tl of the master processor consequently
changes'to "L" (circuit R40,54,55,59,63,
and

IClOb).

the direction of the drawer movement.

n^ox

Q6,^Q7,

In response the master processor reverses

SECTION 3/4

3.3
The SERVO 2 PCB

radial control and the IR receiver.

3.3.1 Radial control
A moving arm allows the laser pick-up to follow the

track horizontally. This arm basically functions like
a moving coil instrument.

The radial-control circuit can be subdivided into four

blocks:

- Radial control circuit

- AGC circuit

- Offset control circuit

- Track detection circuit

3.-3.2

The value of the radial-error signal can be computed
as follows^ RE= kd (II +12+13 +14) - k (II + 12).
The value of k is determined by the AGC circuit, and
d by the offset control circuit.
RAD-ERR2 =11+12
RAD-ERR1 =13+14
The signals RAD-ERR1 and RAD-ERR2 are summed via the
circuit IC9b, R58/59/61/62/63 and Q6. The sum flows as a
current through R63 and Q6. The error signal RAD-ERR 2 is
converted via R55 and R57 to a current that flows through
R54 and transistor E of IC8. The factor k is formed by
transistors A and B as well as C and D
formed by Q5 and transistor F
The signal RAD-ERR 2 x k (=k [II + 12]) on pin 10 of IC9c
appears on pin 9 of IC9c; the signal [RAD-ERR1 +
RAD-ERR2J kd (= kd [11 + 12 + 13 + 14j) appears on pin 10
of IC9c. The difference signal (RE), developed in IC9c,
appears on Pin 8 (RE = kd [II + 12 + 13 + 14 j - K[I1 +
K2j ). The "lag" network of the radial control is

implemented by R66, R67, R68, C15, and IC9d, the "lead"

network by R69, R7
IC5 through the protective diodes D5 and D6. The signal

is^taken through switch B (IC5) to pin 2 of IC2 which

together with Q2, Q3; R6, R7", R8, RT1, and C5 constitutes
the_output stage for the radial-control signal RAD-MOT+/

-RAD-MOT-.
disabled (Signal
forward and reverse mode. The laser pick-up can be
positioned during this phase with the signals RC-1, RC-2,
CUR-DIR, and CUR-SUM.

SERVO-2 PCB

Radial-control circuit

RT1 protects the

1.769.330

1.769.330

0,

RC-o).

contains the circuits for

and C16. The signal is conducted to

coil;-

This occurs in search, pause,

(IC8).

(IC8),

ThJBMwontrol can be

factor d is

KEI/OX

B225

3.3.3 Automatic gain control (AGC) circuit
The bandwidth of the radial-control circuit is stabilized

by this circuit. A 650 Hz sine-wave signal is generated

in the circuit IClOc, IClld, C22,

R86,

R87? R90, and R91. As the gain increases or

C23# C24, C25,

R85

r

decreases the phase relation of the supplied signal
becomes also larger or smaller with respect to the
returning signal* The two signals are compared in the
phase detector (ICll) and a new signal is developed.
The latter is proportional to the phage and also to the
gain.

This signal controls the factor k. The gain is laid,

out for a" phase shift between the signals -of -.135° The

650 Hz.sine-wave signal is therefore fed into the control
loop at pin 13 of IC9d through a 45° phase shifter (R84,
C21).

The phase shift is 90° at the input of the phase

detector. The 650 Hz sine-wave signal is eliminated from

the control circuit through a bandpass (IClOd,
R83,

C19, C20) and converted in IClla to a square-wave

signal.

This square-wave signal is input to the phase

R82

r

comparator (ICllc, pin 8). The phase reference is

supplied by pin 9 of ICllc.

3.3.4 Offset control circuit
The asymmetry of the reflected laser beam is corrected

by this circuit to ensure that the laser beam is kept
exactly on the center of the track. The difference
between minimum and maximum reflection is the greatest

(presence of pit = minimum reflection, between pits

= maximum reflection) when the laser beam follows exactly
the center of the track.

SECTION 3/5

Through the 650 Hz sine-wave signal the moving arm
oscillates with an amplitude of 0.05 jim.

If the laser beam is on the track center, all half-waves

of the filtered out signal are folded to the same

(positive) side. If the laser beam is to the right of the

track center, the signal is in~phase with the 650 Hz
oscillations of the moving arm, or antiphase if the beam

is on the left of the track center.

The voltage across R63 is proportional to the reflected
light intensity

through IC6a,

(11 + 12 + I3 + I4).

R30f R31r and

The voltage is amplified

R64# and the 650 Hz component
is filtered out in a bandpass (R32, R33, R34, R35, R37,
Cll,

C12, and

IC7b).

The filtered signal is inverted

through lC7ar R36, and R38. The former and the

noninverted signal are taken to switch C of IC5. The
output of this switch (IC5, pin 4) is integrated through

IC7d and C.30 and determines the factor d (Q5 and

transistor' F of IC8). The status of switch C (IC5)

is controlled by the 650 Hz signal in the control loop

. -vara-the bandpass

R42f R43r R44 , R45, C13, C14 , D4,

" and IC7c.

WT^ZJ'jLTi R^OX

B225

3 . 3.5 Track detection circuit

The tracks which are skimmed over by the laser pick-up
are read through the interrupt input of the slave
processor

(TRK-SIG).

This signal is generated from the

signal available at IC6, pin 1 (proportional to

[

I1 +

I2

is

+ I3 + I4J

,!L,!

when no error location is detected on the CD.

),

the DO and the HFL signal. The signal DO

The HFL signal is "H" when the HF signal is large enough.
The TRK signal is only "L" when the HE signal is too
small.
location is detected on the CD

For each skipped track, HFL is "L" if no error

(DO="L").

The radial-error
signal RE (IC9c, pin 8) informs whether the laser scanner
is positioned to the left or the right of the track. The
signal required for this purpose (RAD-POS) is generated
via IC3c, R12, R19, and R20 from the radial-error signal.

3.4 Preamplifier and laser PCB 1.769.100.35
This board comprises the following circuits:

- Laser control

- Signals for focus and radial control

- HF signal amplifier

SECTION 3/8

3.4.1 Laser control
The laser diode is supplied via Q4. The intensity of

the laser light can be checked through the "monitor

photo diode" and adjusted with the trimmer potentiometer

R8CT.

The signal LAS-OFF (from PCB

1.769.310

/ IC1) switches
the laser on or off. If the intensity of the laser
becomes too small, the current flowing through the
monitor photodiode decreases correspondingly. The voltage
across R84 also drops. The output of.opamp IC3a
consequently becomes more positive and Q4 more
conductive. The intensity of the laser is adjusted by
discharging some of the current through the monitor
photodiode via R80 and R81.

3.4.2 Focus and radial-control signals

The following signals are generated by this circuit;

- FOC-ERR

- RAD-ERR1

- RAD-ERR2
The currents of the four photodiodes (Al to A4) are

amplified in IC1. The corresponding error signals are
developed by the subsequent network. The focus error
signal is proportional to (11+14) -

(12+13).

13 + 14
constitutes the•RAD-ERRl signal, II + 12 the RAD-ERR2
signal.

The gain of the focus control loop can be

-^djiis/ted with R58, the balance with R41 (not included in

'all

versions).

" '3-4.3 HF signal amplifier

The circuit comprising transistors Ql through Ql consti­tutes the signal amplifier with bandpass characteristic.
Low-frequency (e.g. control signals of the servos)
and high-frequency disturbance signals are consequently
filtered out.

3.5 Decoder PCB

1.769.300

The decoder PCB contains the following circuits:

- Digital signal processing

- Digital sine-wave generator

- HF£ and DO detector

mnruiDjiMM HEMOX B225 SECTION 3/7

3.5.1 Digital signal processing

The HF signal is converted in IC13 (SAA 7010} into
diqital siqnals and split into audio and information
data (subcode, for the slave

signal is also regenerated in JC13. The audio data

are brought into the correct time slot pattern. Corrupted
audio data are not recognized in 1C12 and corrected

if necessary. Should the errors be incorrigible, the

missing sample values are replaced in. IC10 (SAA 7000)
through interpolation. Should this also be infeasible,
the HF signal is slowly muted (soft
of the CD motor is controlled by the signal MCES (IC1,
pin

4 )

.

3.5.2 Digital sine-wave generator
The PROM (IC4) contains a value table for the sine-wave

signal which represents the maximum possible level

of a CD.

The circuit consists of IC5 through IC9 with IC5 and

IC6 supplying the addresses for the PROM. Parallel/serial
data conversion is performed in IC3. The change-over
between audio data from the CD and the 1 kHz sine-wave

signal is controlled by IC1.

3•5•3

HFL and DO detector

The HF signal is fed into the inverting differential

amplifier Ql and Q2 through C6 and R2. The output signals

are DC-decoupled via C8 and C9 respectively and tied
to DC ground via D2 and D3. D4 and D5 or D6 and D7
respectively constitute a full-wave rectifier each
through which the capacitors C10 or Cll are charged.
With a normal HF signal the DO signal is "LSi and the
HFL signal is "H". If the HF signal drops to approxi­mately 70% of the normal value, the HFL signal also
changes to

!,Lt!

.

Only when the HF signal drops to
approximately 10% of - the normal value does the DO signal
change to "H".

To prevent the output signals of IC11 from being

influenced too strongly by minor contaminations (e.g.

fingerprints) on the CD, transistor Q3 has been added to
the output. When the RF level is at nominal value, pin 7
of IC11 is

"Hl! .

Q3 becomes conductive and the circuit

with Cll receives a smaller time constant. With level
fluctuations caused by minor contaminations, the levels

of the two input capacitors fluctuate in parallel, but

neither the DO nor the HFL signal are affected.

processor).

muting).

The CLOCK

The speed

3.6 DAC PCS

Tfee"

following'circuits are implemented on this PCB:

1.769.280

.

- Digital filtering (oversampling) and digital/analog

- •conversion

- Level adjustment and headphones" aTifffiifier

3.6.1 Digital filtering (oversampling) and D/A conversion

IC1 (SAA 7030) contains two identical filters for both

channels. These filters feature 3 sections:

~ Oversampling section

- Transversal digital filter

- Noise shaper

After each scanning cycle, the new sample values are

inserted by interpolation into the 16-bit information

arriving from the decoder. The scanning rate thus becomes

4 times greater (4 x 44.1 kHz = 176.4 kHz). The spectral
lines above 20 kHz up to 176.4 kHz - 20 kHz are filtered

out by the transversal filter. The sample values are
truncated to 14

bits.

The noise shaper subsequently
delays the truncation error by the scan duration and
negatively added to the next sample value. The
guantisizing noise caused by truncation is thereby
largely shifted toward the frequency range above 20 kHz.
The digital signal is converted in IC101 or IC201

(TDA 1540) to an analog signal. In order to filter out

the residual frequency component at n (176.4 kHz
+; 20 kHz), a low pass of the third order (Bessel filter)
has been added to the converter output.

r'r:;T*5^

The preemphasis is corrected with the circuit illustratec
in Fig. 3.13. The subcode on the CD specifies whether
the selection was recorded with or without preemphasis.
The characteristic of the corresponding filter can
be adjusted with the PREEM signal.

3.6.2 Level adjustment and headphones amplifier

The volume is controlled by a DUAL D/A converter

(AD7528).

corresponding input (IC103a, pin 2 = left-hand channel
/ IC 203bf pin 6 = right-hand
feedback resistances of both opamps remain unchanged
which means that the level can only be attenuated with
this circuit. The dual D/A converter is controlled by a
CMOS shift register through the signals DLEN-3, DATA, and

CLK. The circuit illustrated in Fig. 3.14 constitutes the
output amplifier for the headphones socket and also
the VARIABLE OUTPUT* The signal is also attenuated for
this purpose through a voltage divider so that the signal

is the same (2 V RMS) at both outputs (FIXED and
VARIABLE).
to prevent power-on switching clicks. When power is
applied., the relay is selected by the

KILL signal (which rises to +5 V after approximately

1 to 2
through-connected when the supply voltages are stable.

R^QX

It serves as an attenuator before the

channel).

The signal is taken through relay Kl in order

seconds).

As a result, the outputs are only

The negative-

B225

SECTION 3/8*

REI/OX

4.

TEST POINTS, ADJUSTMENTS ON

4 m i

Test points on B225

B2 2 5

4.1.1 Test points on SERVO 1 PCB 1.769.310

B225

SECTION 4/1

'lDj[j

If no CO is mounted when PLAY is selected* the signals on TP26

an

CJ

2 7 become ^l?V in four intervals of approximately one second

each • "

R^OX

B225

SECTION 4/2

(*) In PLAY- mode* the signal pattern of these test points depends

on the wobble of the mounted compact disc*

w^rumi

4.1.2 Test points on SERVO 2 PCB 1.769.330

R^OX

B225

SECTION 4/3

h FtEMOX

B225

SECTION

4/4

when signals

•4.3V occur

4.13 Test points on MICmPRGCESSQR PCB 1.769.320,

are

on

received froni

TP52«

the IR-

remote control t pulses

of

R^OX

6225

SECTION

4/5

^T'^\£:WM REl/OX

B225

'

SECTION 4/6

Test with reference CD part No. 46241

Black dots

are

located

on

track 17

of

the disc surface* The

following should be measured v^hen this track is played:

WUMEM

FIEMQX

B225

SECTION

4/7

L

^£=.1^

FIEMQK

B225

SECTION 4/8

4.1.5 Test points on DAC PCB

1,769.280

The internal calibration must be switched on for the
following measurements;

=

c^.

4 m2 Adjustments on CD player B225

Note:

Cleanliness
and ensures that

can enter into the

KEI/OX

in

the work area

no

contaminants

CD

mechanism.

is of

or

B225

outmost importance

metal particles

SECTION 4/9

If any work
it

is

(refer

Before putting the

on

essential

to

last page

printed circuit boards
to

observe the ESE recommendations

of

contents).

CD

player into operation ensure

is

necessary,

that the transport screws have been unfastened.
The

CD

bearings which should not

player mechanism

If the drawer must
to perform certain measurements

•rear light barrier must
responds
disc must

as if

be

the drawer were closed) and the compact

secured with a removed adhesive magnet.

The optical system

is

equipped with self-lubricating

be

lubricated.

be

open and a disc mounted

be

of

the laser can

or

adjustments,

interrupted (the detector

be

in

order

the

cleaned with

an air brush.

Coil Ll on the decoder PCB
aligned by IC13 (SAA7010) and consequently requires
no adjustment*

4.2.1 Aids

-

DC

voltmeter

1.769.300

is automatically

- Cathode ray oscilloscope

- Reference CD, frequency response, part No. 46240

- Reference CD, drop

- Mirror

No.

- Set

CD

for adjusting the optical system, part

46242

of

service PCBs and cables, part No. 46230

outs,

part No. 46241

- ESE work location kit, part No. 46200

4.2.2 Aligning

player mechanism, general

- Remove top cover.

- Connect

CD

player

to AC

supply and open the drawer

by pressing the LOAD key.

- Cover rear light barrier.

- Mount reference disc 5 (part No. 46241) and secure

it with a removed adhesive magnet.

- Selection

work.
LOOP.-command

1 of

It

is, therefore^ advantageous

the

CD is to be

in

programming mode.

played for all alignment

to

enter

the

"4T2". 3 Adjusting the laser current

- Switch
and reinsert

- Connect

- Adjust the voltage

CD

player off, remove SERVO 2 PCB

it

DC

via the service PCB (part No.

voltmeter

to

to

500

R63

mV

on

SERVO 2 PCB.

+50

1.769.330

mV

with the trimmer

46230).

potentiometer RS0 (on player mechanism 1.769.100.35).

Adjustments should only

be

made

if

the measured voltage

is outside the specified tolerance range.

CAUTION:
Voltages above 550

mV

shorten the life

of

the laser

pick-up.

- Switch

4.2.4 Adjusting the balance (if trimmer

CD

player off and reinstall SERVO 2 PCB.

is

present)

- Set potentiometer R41 (on player mechanism

1.769.100.35)

to

its center position.

REMGX

B225

4.2.5 Adjusting the focus gain

-- Switch CD player off, remove SERVO 1 PCB 1.76 9.310
and reinsert it via the service PCB.

- Connect AF generator to the X input of an oscilloscope
and via an R-C-R element (according to Fig. 4.12)
to pin 6 of IC2 (on

1.769.310),

(f=600 Hz +5 Hz,

U=250 to 300 mV RMS).

- With trimmer potentiometer R58 (on player mechanism
PCB 1.769.100.35), align for minimum amplitude A
of the Lissajous figure.

SECTION 4/10

, 2 .

6 Checking the angle alignment

t

Place the mirror on the focussing unit and mount
the optical system alignment disc (secure with adhesive

magnet) .

Place the player mechanism below? a light source that
produces a linear, straight shadow.
Bring the-laser scanner arm to its center position
and rotate the CD player in such a way that the arm
stands parallel to the line below? the light source

(refer to Fig.

4.13).

When the reflection on the glass disc and in the
mirror is viewed as illustrated in Fig. 4.13. The
distance between the two lines should not exceed 2.5 mm.

Position the CD player in such a way that the shadow

forms a 90° angle to the scanner arm (see Fig.

4.14).

The distance between the two lines (reflections)

should not exceed 2.5 mm.

^-yiLr^Ju

The angle alignment must be corrected if the deviation

is too large:

- Unfasten screw [A] until the support plate [ B]

be shifted.

- The support plate can now be shifted according to
Fig*
is correct.

- The angle alignment must be rechecked after the
foregoing adjustments have been made.

4.2.7 Adjusting the DC component of the focus signal

- Connect DC voltmeter to Rl (SERVO 1 PCB 1.76

The following adjustment is only necessary if the DC
deviation exceeds
is not possible.

- Adjust the axial set screw of the disc motor in such
a way that 0 V +_50 mV is measured.

- If the motor is replaced, perform the adjustments
according to 4.2.6 and 4.2*7*

4.3 Measuring the audio data

R^OX

4.5. Retighten the screw [A] when the position

+JL4 0

mV. Replace the motor if alignment

B225

can

9.310).

SECTION 4/11

4.3.1 Aids

-_ Reference CD, part No. 46240

- Automatic distortion meter (e.g. Tektronix AA 501;

the RESPONSE button must be in the RMS position for

all measurements)

- Measuring filter (for distortion measurement)

~ Frequency counter

- Oscilloscope

4.3.2 Harmonic distortion

- Measuring arrangement according to Fig. 4.16

- Adjust for maximum level with VOLUME + key

- Mount reference disc (part No.
4 for measuring the left-hand channel and track 8

for measuring the right-hand channel.

- The harmonic distortion should be less than 0.006%.

4.3.3 Output level

- Press CAL TONE button and adjust for maximum level

with VOLUME + key.

- The level of the FIXED and VARIABLE outputs should
be 2 V RMS +10%. The balance between channels should be

better than 0.2 dB.

4^,3 . 4 -Frequency response

- Adjust for maximum level with VOLUME + key.

"'-—The calibration tone (1 kHz) serves as the 0 dB

reference.

- Play tracks 4 and 8 (CD part No. 46240) and measure

the outputs FIXED and VARIABLE. The frequency response

shoul-d be within +0 to -X3.6 dB.

46240).

Play track

?rr-S-£:JL\Fi FI&/OX B225 ! SECTION 4/12*

4.3.5 Cross talk

- Adjust for maximum level with VOLUME + key,

- Reference = CAL TONE 1000 Hz)

- Measure both outputs across a 30 kHz low-pass:
Play track 8 for measuring cross talk R -> L

Play track 4 for measuring cross talk L -> R

- The cross talk attenuation should be at least 90 dB.

4.3.6 Signal-to-noise ratio, linear

- Maximum volume, reference = CAL TONE 1000 Hz.

- Play track 18 and measure the outputs FIXED and
VARIABLE via a 30 kHz low-pass.

- The measured value should be higher than -96 dB,

4.3.7 Signal-to-noise ratio, weighted

- Maximum volume, reference = CAL TONE 1000 Hz.

- Play track 18 and measure the outputs FIXED and

VARIABLE via an A filter.

- The measured value should be higher than 100 dB,

4.3.8 Phase linearity

- Connect oscilloscope to one of the outputs.

- Play track 20 and visually assess the square-wave

signals at 100 Hz, 400 Hz, 1002 Hz, and 5512 Hz.
The curve should be shaped symmetrically (see
Fig.

4.17).

, .

4.4 Listening test with reference CD (part No. 4 6241)

The reference CD simulates the following errors for

checking the error correction system:

- Information gaps with a length of 400 to 900 pm (tracks
5 through 9)

- Black dots from 300 to 800 micrometers

(tracks 1*1 through track 17)

- Simulated fingerprint (tracks 18 and 19)

The simulated defects should not cause any drop-outs

(reproduction

can for example be caused by the following errors:

- IC13 (SAA 7010,
with PLL defect.

- HFL an DO detector defective.

gaps).

If drop-outs become audible, this

demodulator),

clock regeneration