Pioneer CX-938-A Service manual

Model Service Manual CD Mechanism Module Mechanism Unit CDX-P1250/X1N/UC,ES CRT2318 CXK4900 CXB3008 CDX-P1250/X1N/EW CXK4905 CXB3008 CDX-FM1259/X1N/UC CRT2320 CXK4916 CXB3008 CDX-FM1257/X1N/UC,ES CXK4915 CXB3008

PIONEER ELECTRONIC CORPORATION 4-1, Meguro 1-Chome, Meguro-ku, Tokyo 153-8654, Japan

PIONEER ELECTRONICS SERVICE INC. P.O.Box 1760, Long Beach, CA 90801-1760 U.S.A. PIONEER ELECTRONIC [EUROPE] N.V. Haven 1087 Keetberglaan 1, 9120 Melsele, Belgium PIONEER ELECTRONICS ASIACENTRE PTE.LTD. 253 Alexandra Road, #04-01, Singapore 159936

C PIONEER ELECTRONIC CORPORATION 1999

K-ZZU. FEB. 1999 Printed in Japan

ORDER NO.

CRT2357

CD MECHANISM MODULE

CX-938

- This service manual describes the operation of the CD mechanism incorporated in models listed in the table below.

- When performing repairs use this manual together with the specific manual for model under repair.

CONTENTS

1. CIRCUIT DESCRIPTIONS...........................................2

2. DISASSEMBLY .........................................................18

3. MECHANISM DESCRIPTIONS.................................23

C X-938

1. CIRCUIT DESCRIPTIONS

The LSI (UPD63710GC) used on this unit comprises five main blocks ; the pre-amp section, servo, signal processor, DAC and CD text decoder (not used on this model). It also equips with nine automatic adjustment functions.

1.1 PRE-AMP SECTION

This section processes the pickup output signals to create the signals for the servo, demodulator and control. The pickup output signals are I-V converted by the preamp with the built-in photo-detector in the pickup, then added by the RF amp to obtain RF, FE, TE, TE zero cross and other signals. This pre-amp section is built in the servo LSI UPD63710GC (IC201). The following describes function of each section. Since this system has a single power supply (+5V), the reference voltage for this LSI and pickup are set to REFO (2.5V). The REFO is obtained by passing the REFOUT from the LSI through the buffer amplifier. The REFO is output from Pin 89 of this LSI. All measurements are done using this REFO as reference. Note : During the measurement, do not try to short the REFO and GND.

1) APC Circuit (Automatic Power Control)

When the laser diode is driven with constant current, the optical output has large negative temperature characteristics. Thus, the current must be controlled from the monitor diode so that the output may be constant. APC circuit is for it. The LD current is obtained by measuring the voltage between LD1 and V+5. The value of this current is about 35mA.

AGCI

RFO

C-3T

FEO

FE-

TEO

TE-

82 83

RF-

EQ1

EQ2

AGCO

RFI

ASY

EFM

PEAK DET.

LPF

BOTTOM DET.

S/H

D/A

A/D

D/A

A/D

TE2

VREG

GND APN

LDON

EFM

DEFECT

FOK

A3T

MIRR

To the following stage of the LSI

Vref

·····Vref(+2.5V)

VREG GND AMP_PN

(H:Nch L:Pch)

LDON (H:LD MOVE L:STOP)

Vref

·····Vref(+2.5V)

R102 10 R101 12

Q101

2SB1132

C102

0.1µF

C103 100µF/6.3V

PU UNIT

R103

2.2k

C105

0.33µF

+5V

110k

3pF

150k

100k

16k

Fig.1 : BLOCK DIAGRAM OF BUILT-IN RF AMPLIFIER

Fig.2 : APC CIRCUIT

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2) RF Amplifier and RFAGC Amplifier

The photo-detector outputs (A +C) and (B +D) are added, amplified and equalized on this LSI and then output to the RFI terminal as the RF signal. (The eye pattern can be checked by this signal.) The RFI voltage low frequency component is :

RFI = (A

+B +C +

D) ×3.2 RFI is used on the FOK generator circuit and RF offset adjusting circuit. R215 is an offset resistor for maintaining the bottom reference voltage of the RFI signal at 1.5 VDC. The D/A output used for the RF offset adjustment (to be described later) is entered via this resistor. After the RFI signal from Pin 77 is externally AC coupled, entered to Pin 76 again, then amplified on the RFAGC amplifier to obtain the RFO signal. The RFAGC adjustment function (to be described later) built-in the LSI is used for switching feedback gain of the RFAGC amplifier so that the RFO output may go to

1.5

0.3Vpp. The RFO signal is used for the EFM, DFCT, MIRR and RFAGC adjustment circuits.

3) FOK Circuit

This circuit generates the signal that is used for indicating the timing of closing the focus or state of the focus close currently being played. This signal is output from Pin 4 as the FOK signal. It goes high when the focus close and in-play. The RFOK signal is generated by holding DC level of the RFI at its peak with the succeeding digital section, then comparing it at a specific threshold level. Thus, the RFOK signal goes high even if the pit is absent. It indicates that the focus close can take place on the disc mirror surface, too. This signal is also supplied to the micro computer via the low pass filter as the FOK signal and used for the protection and the RF amplifier gain switching.

CN101

10k

FOK

CIRCUIT

A/D

A+C

16k

B+D

10k

16k

10k

R215

12k

C209 3pF

R214 10k

R207

1.8k

C208 27pF

R213 10k

80 79 74757677

D/A

12k

10k

RFOAGCIRFI

C207

0.22µF

C206

3900pF

FOK

TO EFM CIRCUIT

Fig.3 : RFAMP, RFAGC AND FOK CIRCUIT

5) Tracking Error Amplifier

The photo-detector outputs E and F are passed through a differential amplifier and an error amplifier, and then (E −F) is output from Pin 93 as the TE signal. The TE voltage low frequency component is :

(E −F)

××

(E −F) ×5.7 (Effective LSI output is 5.0). Using REFO as the reference, the TE waveform of approximately 1.3 Vpp is obtained for the TE output. The final-stage amplifier cutoff frequency is 20 kHz.

6) Tracking Zero Crossing Amplifier

TEC signal (the tracking zero crossing signal) is obtained by multiplying the TE signal four times. It is used for locating the zero crossing points of the tracking error. The zero cross point detection is done for the following two reasons :

To count tracks for carriage moves and track jumps.

To detect the direction in which the lens is moving

when the tracking is closed (it is used on the tracking brake circuit to be described later).

The TEC signal frequency range is 300 Hz to 20 kHz.

TEC voltage

TE level ×4 Theoretical TEC level is 5.2V. The signal exceeds Drange of the operational amplifier and thus is clipped. It, however, can be ignored since this signal is used by the servo LSI only at the zero crossing point.

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Fig.5 TRACKING ERROR AMPLIFIER AND TRACKING ZERO CROSSING AMPLIFIER

4) Focus Error Amplifier

The photo-detector outputs (A+C) and (B+D) are passed through a differential amplifier and an error amplifier, and then (A

+C−B−

D) is output from Pin 91 as the FE signal.

The FE voltage low frequency component is :

= (A + C − B − D) ××

(A + C − B − D) × 5

Using REFO as the reference, an S-curve of approximately 1.5 Vpp is obtained for the FE output. The final-stage amplifier cutoff frequency is 11.4 kHz.

20k

CN101

10k

20k

A+C

16k

B+D

48k

16k

10k

9190

D/A

80k

110k

C210 220pF

R208 300k

A/D

FE OFFSET

TO DIG. EQ

48k

38k

CN101

56k

38k

224k

48k

224k

56k

9392

D/A

80k

110k

C211 100pF

A/D

TE OFFSET

TO DIG. EQ

48k

R216

27k

R215

27k

60k

20k

TE2

TEC

R212

C212

6800pF

16k 10k

(80k//300k)

20k

Fig.4 : FOCUS ERROR AMPLIFIER

224k

(56k

+27k)

80k 38k

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7) DFCT (Defect) Circuit

The DFCT signal is used for detecting defects on the mirrored disc surface. It allows monitoring from the HOLD pin (Pin 2). It goes high when defects are found on the mirrored surface. The DFCT signal is generated by comparing the RF amplified signal (which is obtained by bottom holding the RFO signal) at a specific threshold level by the succeeding digital section. Stains or scratches on the disc can constitute the defects on the mirrored disc surface. Thus, as long as the DFCT signal remains high in the LSI, the focus and tracking servo drives are held in the current state so that a better defect prevention may be ensured.

8) 3TOUT Circuit

The 3TOUT signal is generated by entering disturbance to the focus servo loop, comparing phase of fluctuations of the RF signal 3T component against that of the FE signal at that time, then converting the signal to DC level. This signal is used for adjusting bias of the FE signal (to be described later). This signal is not output from the LSI, thus its monitoring is not available.

9) MIRR (Mirror) Circuit

The MIRR signal shows the on track and off track data, and is output from Pin 3. When the laser beam is

On track : MIRR ="L" Off track : MIRR

"H" This signal is used on the brake circuit (to be described later) and also as the trigger to turn on track counting when jumping take place. The MIRR signal is supplied to the micro computer, too, for the protection purpose.

A/D

MIRR

CIRCUIT

DFCT

CIRCUIT

BOTTOM DETECT

PEAK DETECT

LPFS/H

A/D

40k

20k

40k

200k

C205

0.1µF

C3T

AGCI

RFO

12k

10k

20k

30k

MIRR

HOLD

Fig.6 : DFCT, MIRR AND 3T DETECTION CIRCUIT

Fig.7 : HOLD OUTPUT WAVEFORM

(When surface defects are present)

Fig.8 : MIRR OUTPUT WAVEFORM

(When an access is made)

Surface defects

RFI

HOLD

RFI

MIRR

OFF Track ON Track

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10) EFM Circuit

This circuit is used for converting the RF signal to digital signal consisting of “0” and “1”. The RFO signal from Pin 75 is externally AC coupled, entered to Pin 74, then applied to the EFM circuit. Loss of the RF signal due to scratches or stains on the disc, or vertical asymmetry of the RF due to variations in the discs manufactured can’t be eliminated by AC coupling alone. This circuit, therefore, controls the reference voltage ASY on the EFM comparator by use of the fact that “0” and “1” appear fifty fifty in the EFM signal. By this arrangement, the comparate level is constantly maintained at almost center of the RFO signal level. The reference voltage ASY is generated when the EFM comparator output is passed through the low pass filter. The EFM signal is output from Pin

71. It is a 2.5 Vp-p amplitude signal centering on REFO.

RFI

40k

C206

3900pF

ASY

EFM

40k

15k75k

R205

10k

R206

39k

C203

0.1µF

C204

3300pF

EFM. SIG

Fig.9 : EFM CIRCUIT

C X-938

1.2 SERVO SECTION (UPD63710GC : IC201)

The servo section controls the operations such as error signal equalizing, in focus, track jump and carriage move. The DSP is the signal processing section used for data decoding, error correction and interpolation processing, among others. This circuit implements analog to digital conversion of the FE and TE signals generated on the pre-amplifier, then outputs them through the servo block as the drive signal used on the focus, tracking and carriage system. The EFM signal is decoded on the signal processing section and finally output via the D/A converter as the audio signal. The decoding process also generates the spindle servo error signals which is fed to the spindle servo block to generate the spindle drive signal. The focus, tracking, carriage and spindle drive signals are then amplified on the driver IC BA5986FM (IC301) and fed to respective actuators and motors.

1) Focus Servo System

The focus servo main equalizer is consisted of the digital equalizer. Fig.10 shows the focus servo block diagram. When implementing the focus close on the focus servo system, the lens must be brought within the in-focus range. Therefore, the lens is moved up and down according to the triangular focus search voltage to find the focus point. During this time, the spindle motor is kicked and kept rotating as a set speed. The servo LSI monitors the FE and RFOK signals and automatically carries out the focus close at an appropriate point. The focus closing is carried out when the following three conditions are met :

The lens approaches the disc from its current position.

RFOK

"H"

The FZC signal is latched at high after it has once

crossed the threshold set on the FZD register (Edge of the FZD).

As the result, the FE (

REFO) is forced to low.

AMP

DIG.

A+C B+D

FOP

FOM

IC301

BA5986FM

LENS

IC201 UPD63710GC

FOCUS SEARCH

TRIANGULAR

WAVE GENERATOR

DAC

CONTROL

A/D

R302

15k

R301

10k

Fig.10 : FOCUS SERVO BLOCK DIAGRAM

C X-938

When the above conditions are all met and the focus is closed, the XSI pin goes to low from the current high, then 40 ms later, the microcomputer begins to monitor the RFOK signal after it that has been passed through the low pass filter. When the RFOK signal is recognized as low, the micro computer carries out various actions including protection. Fig.11 a series of operations carried out relevant to the focus close (the figure shows the case where focus close is not available). You can check the S-curve, search voltage and actual lens behavior by selecting the Display 01 for the focus mode select in the test mode, and then pressing the focus close button.

REFO

LENS POSITION RELATIVE TO DISC

NEAR

FAR

"JUST FOCUSED"

REFO

Expanding around "Just Focused Point"

REFO

RFI

FOK

FZD THRESHOLD LEVEL

FZD (INTERNAL SIGNAL)

Focus closing would normally take place at these points

XSI (IN THE EVENT FOCUS IS CLOSED)

LEVEL

Fig.11 : FOCUS CLOSE SEQUENCE

C X-938

2) Tracking Servo System

The digital equalizer is employed for the main equalizer on the tracking servo. Fig.12 shows the tracking servo block diagram.

a) Track jump

When the LSI receives the track jump command from the microcomputer, the operation is carried out automatically by the auto sequence function of the LSI. This system has five types of track jumps used for the search : 1, 4, 10, 32 and 32 ×3. In the test mode, in addition to three jumps (1, 32 and 32

3), move of the carriage can be check by mode selection. For track jumps, the microcomputer sets almost half of tracks (5 tracks for 10 tracks, for instance) and counts the set number of tracks using the TEC signals. When the microcomputer has counted the set number of tracks, it outputs the brake pulse for a fixed period of time (duration can be specified with the command) to stop the lens. In this way, the tracking is closed and normal play is continued. To improve the servo loop retracting performance just after the track jump, the brake circuit is turned on for 50 ms after the brake pulse has been terminated to increase gain of the tracking servo. Fast forward and reverse operations are realized by through consecutive signal track jumps. The speed is about 10 times as fast as that in the normal mode.

TOP

TOM

IC301

BA5986FM

LENS

R304

15k

R303

10k

AMP

DIG.

F E

IC201 UPD63710GC

JUMP

PARAMETERS

DAC

CONTROL

A/D

GAIN NORMAL

KICK

BRAKE

TEC

T. BRAKE

EQUALIZER

T. SERVO

CLOSED

OPEN

NORMAL

GAIN UP

OFF

TEC

(10 TRACK)

EQUALIZER

T. BRAKE

SERVO

2.9mS (4.10 TRACK JUMP)

5.8mS (32 TRACK JUMP)

GAIN UP

NORMAL ON

OFF OPEN

CLOSED

50mS

Fig.12 : TRACKING SERVOBLOCK DIAGRAM

Fig.13 : SINGLE TRACK JUMP

Fig.14 : MULTI-TRACK JUMP

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