Akai CD17 ADJUSTMENT

2-8. OPERATIONAL AMPLIFIER COMPARATOR

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TA 75393S

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- 15 -

SECTION 3 ADJUSTMENT PROCEDURES

BE SURE

The compact disc player reads
exposed
ped
microcomputer). When
the laser diode does
The laser diode emits

1)

2)

it

the

disc with laser beam. When PLAY

TO

to the

to

prevent

The

Disc tray

The

optical piek

(PUSL) sensor

disc

is not

FOLLOW CAREFULLY

laser beam. Especially

the

unnecessary laser putput.

the pin 42 is. Low, the

not

emit

the

the

beam when

is

perfectly closed

up is

located

is

short).

found,

it

does

THE

the

disc signal

the

beam. After

the

following conditions

(The

at the

not

emit

key is

pressed,

INSTRUCTION BELOW BEFORE SERVICING

-SAFETY INTERLOOK

by

detecting

human eyes

The

laser diode emits

the

unit

leaf switch

vicinity

the

laser beam.

the

the

laser beam.

can be

laser beam outputs

is

of the
of the

laserdiode emits

badly affected

the

powered,

But if the

the

are met.

close sensor

disc driving motor

-

are

laser beam.

unitial state

is

short).

DISO

is

loaded

the

beam again.

It

must
by the
controlled

On the
of pin 42 is

(The

in the set, the set

AND

ADJUSTMENT.

be

avoided

laser beam. Therefore,

by the pin 42 of

contrary, when

leaf switch

for the

HIGH.

of the

the pin 42 is

pick-up slide limite

reads

human body

the

unit

is

103001

the

(one

directory

to be
equip-

chip

HIGH,

of the

>

>-^vW-

+5V

OPEN

->i-

PLAY

LED

<ïo)

<8)

IC 3001

-(V

LOW : ACTIVE

POWER ONAFF

SWITCHING

DEVICE

POWER

SUPPLY

t

AC i

DIODE

-

16 -

1.

CONFIRMING LASER OUTPUT

1) Make the LASER output section visible by removing the flap disc damp.

2) Switch on the power and press PLAY key once to get the LASER output. Appiying the sensor of optical power meter
to the objective lens, make sure that the output is in the range of 0.25mW and 0.5mW.

3) Reinstall the flap disc damp.

2.

PLL PREE RUN FREQUENCY ADJUSTMENT

1) Short between test pin TP. EFMI of IC 102 (or any lead of R214) and GND, power on and set the unit to STOP mode.

2) Connect a DC voitmeter between center lead of D201

3) Connect a frequency counter between test pin TP. 7 and GND, and rotate the core of the PLL OSC coil (LI04) with a
plastic screwdriver so that frequency is 4.320 MHz to 4.330MHz.

3. FOCUS OFFSET ADJUSTMENT

1) Power on and set the unit to STOP mode.

2) Connect a DC voitmeter and oscilloscope between test pin TP. F and GND.

3) Adjust \/R401 so that the indication of DC voitmeter and oscilloscope is ± lOmV.

TRACK OFFSET ADJUSTMENT

1) Power on and set the unit to STOP mode.

2'

"onnect a DC voitmeter and oscilloscope between test pin TP. T and GND.

3/

Adjust

5. DIFFRACTION GRID ADJUSTMENT
This is a precise adjustment and must be made carefully.

1) Connect AC voitmeter between test pin TP.TEO and GND.

2) Turn the power on, load a disc and set the unit to STOP mode.

3) Press PLAY/PAUSE key.

4) PLAY LED wil! flash. Short between pin No. 4 of IC 109 and GND.

5) Connect the set and oscilloscope according to the picture below.

VR301 so that the indication of DC voitmeter and oscilloscope is ± lOmV.

(SVC-2n)

and GND, and check that voltage is 2.4V to 2.6V.

TPF O

CD

GNDO

PLAYER

PIN NO.9 O

OF ICIOI

10 K 0 0,47

-Vv\ I

lOK

10 K

-'VSA^ 1 I

10 K 0.047

BAND

PASS FILTER

- 17 -

T

T 0.047

-r 0.047

-o

•O

X

G

OSCILLOSCOPE

6) Observe the resurqe waveform of the waveform indicated on the oscilloscope and insert the adiustment jig into the dif­fraction grid and set phase difference at 180°, so that indication on Ac voitmeter is maximum, (see figure 1).

7) Even if the phase difference is 180° in the above step, the E and F subbeams may be mistakenly on the different track.
Be sure that the E and F subbeams are on the same track.

8) Remove the short between pin No. 4 of IC 109 and GND.

9) Observe the waveform of the signal between test pin F and pin No. 9 EFB (E) of IC101 using dualtrace oscilloscope
(Monitored in ALT mode). Beam E and beam F are in the same track if triggering of waveform F is approximately

36.7 jis behind the point (position where waveform hollows out) where waveform E is triggered (see figure 2).

10) When the beams are not on the same track return to step 3), and rotate the adjustment jig at the 180^ point. Repeat

steps 3) to 9) until confirned.

(FIGURE I)

(FIGURE 2)

-18-

6. ADJUSTMENT

1) Turn

the

power

2) Connect

3) Play a selection
maximum.

the

OF

PICK

UP

on,

load a disc

oscilloscope

and

monitor

ANGLE

and

select a track that

or

jitter counter between test

the

waveform

of TP HF and

Is in the

middle position

pin TP HF and GND.

rotate

the

angle adjustment screw

of

disc.

so

that

the

waveform

is at its

7.

E-F

BALANCE ADJUSTMENT

1) Turn

the

power

2) Short between

3) Connect

4) Set the

pin No. 9 of IC 101 and GND.

a DC

Voltmeter

unit

to

PLAY mode, adjust VR101

on,

load a disc

and

TEO

G

and set the

oscilloscope

O

O

unit

to

STOP mode.

to TP TEO

so

that

the DC

22K

•VW

through

voltmeter

220/16

220/16

low

pass filter shown below.

and

oscilloscope

O

-

DC

VOLTMETER

Zfe OSCILLOSCOPE

O

is OV ~

-15mV.

-19-

8. ADJUSTMENT OF FOCUS/TRACKING GAIN
The measurement circuit shown below is necessary for accurate adjustment of the focus and tracking gain.

• Focus

gain

adjustment

1) Connect the measurement circuit shown below, turn the power on, load a disc and set the unit to PLAY

mode.

2) Apply a 900Hz, 0,5Vp-p signa! from signal generator.

3) Observe the resurge wave forms on the osciiloscope, and adjust VR402 so that the phase difference of output of X and Y

from the measurement circuit is 90°.

• Tracking gain adjustment.

1) Adjustment is made in the same manner as for focus gain.

The

input

from the frequency generator is set to 1800Hz 0.5Vp-p, and VR302 is adjusted so

T

ACTUAOR

DRIVE

OUTPUT

CNI04

F

that

the

phase difference

SIGNAL
GENERATOR

DUALTRACE
OSCILLOSCOPE

-20-

SECTION 4 SERVO

1 OUTLINE

CD-17 has four servo circuits.

1.

TRACKING SERVO

Controls the objective lens in the pit track direction, and keeps the laser on the pit track:

2.

FOCUS SERVO.

Controls the vertical movement of the optical system's objective lens for correct focusing on the compact disc.

3. DISC MOTOR SERVO.

To keep a speed of the disc constantly, it is controlled by CLV (CONSTANT LINEAR VELOCITY) servo.

4.

FEED MOTOR SERVO.

The feed motor moves the optical system between the inside and outside circumferences of the disc. By applying servo,
the objective lens deviation in the tracking direction is controlled as nearly as possible to mechanical center, so that
tracking servo works stably.

4-2.

FOCUS SERVO

When the disc is ioaded in the set, first focus search is performed and focus servo is applied.
IVIain detector is devided into four parts of A,B,C and D. We obtain (A + C) and (B -i- D) by using the output of the main detec­tor and it is used in Forus servo.

Exact fous detection is performed by the focus OK circuit and focus zero cross detection circuit. Focus servo amplifies detect­ed signal from photo detector of piek up at the CX-20109 and makes a signal at focus trough subtracting process (differen­tial AMP). This error signal is amplified after

lead,

lag compensatlon and applied to focus actuator coil of the piek up. Then

objective les starts tracing.

VR402 lOOK

The waveform of the point 1 when focus starts

5

V

O

V

FCS

AUTO FOCUSING TPF waveform (for playing)

OV

''ii'»'i*ï

i"ji/i'..i'/'i/:.'i.'|f(('ii'

O

FCS

Output of the FE

X : Distance between disc and

objective lens.

Focus error waveform according to distance

-22-

4-3.

TRACKING SERVO

The signal detected from E and F (photo detector) of the piek up is amplified at CX20109.
After making tracking-error signal through subtraction process, this error signal is amplified after lead and lag compensatlon.
The objective lens traces a track of the disc by driving the tracking-actuator of the piek up.

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220K

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TRACKING
ACTUATOR

YM3815«»20)

(-IIV)

(TRACKING SERVO CIRCUIT)

Y ; Distance between center of a track and center of a

optical beam.

- 23 -

SECTION 5 DIAGRAM

PCB PATTERN & MARKING

. MAIN

- 24 -