Pioneer-CX938-tape-cdm 电路图 维修手册.pdf

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1、ModelService ManualCD Mechanism ModuleMechanism Unit CDX-P1250/X1N/UC,ESCRT2318CXK4900CXB3008 CDX-P1250/X1N/EWCXK4905CXB3008 CDX-FM1259/X1N/UCCRT2320CXK4916CXB3008 CDX-FM1257/X1N/UC,ESCXK4915CXB3008 PIONEER ELECTRONIC CORPORATION4-1, Meguro 1-Chome, Meguro-ku, Tokyo 153-8654, Japan PIONEER ELECTRONI

2、CS 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

3、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. D

4、ISASSEMBLY .18 3. MECHANISM DESCRIPTIONS.23 RadioFans.CN 收音机爱 好者资料库 2 CX-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

5、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 pre- amp with the built-in photo-detector in the pickup, then added by the RF amp to obtain RF,

6、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

7、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 d

8、riven 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

9、 this current is about 35mA. 71 72 74 76AGCI 77RFO 75 78 79 80 73 91 90 93 92 C-3T FEO FE- TEO TE- 85 86 87E 97PD 99PN F D 82 83 84B C A RF- EQ1 EQ2 AGCO RFI ASY EFM PEAK DET. LPF BOTTOM DET. S/H D/A A/D D/A A/D 94 98 TE2 LD VREG GND APN LDON EFM DEFECT FOK A3T MIRR To the following stage of the LSI

10、 Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref Vref(+2.5V) 97 PD 99 PN 98 LD VREG GND AMP_PN (H:Nch L:Pch) LDON (H:LD MOVE L:STOP) Vref Vref(+2.5V) 14 5 R102 10 R101 12 Q101 2SB1132 C102 0.1F C103 100F/6.3V PU UNIT R103 2.2k C105 0.33F +5V 1k 110k 3pF 3pF 150k 100k 100k

11、16k 1k Fig.1 : BLOCK DIAGRAM OF BUILT-IN RF AMPLIFIER Fig.2 : APC CIRCUIT RadioFans.CN 收音机爱 好者资料库 CX-938 3 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

12、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 outpu

13、t 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

14、 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

15、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 threshol

16、d 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 swi

17、tching. CN101 84 18 25 83 82 10k 10k 85 FOK CIRCUIT A/D 4 A+C 16k B+D 10k 16k 10k R215 12k C209 3pF R214 10k R207 1.8k C208 27pF R213 10k 807974757677 D/A 12k 66 10k RFOAGCIRFI C207 0.22F C206 3900pF FOK TO EFM CIRCUIT Fig.3 : RFAMP, RFAGC AND FOK CIRCUIT RadioFans.CN 收音机爱 好者资料库 5) Tracking Error Am

18、plifier 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 : TE = (E F) = (E F) 5.7 (Effective LSI output is 5.0). Using REFO as the reference, the TE

19、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 poi

20、nts of the tracking error. The zero cross point detection is done for the following two reasons : 1 To count tracks for carriage moves and track jumps. 2 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).

21、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 D- range 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. 4 CX-938 F

22、ig.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 com

23、ponent is : FE = (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 84 18 25 83 82 10k 20k 85 A+C 16k B+D 48k 16k 10k 9190 D/A 80k 110k FE C210 220pF R208 300k A

24、/D FE OFFSET TO DIG. EQ48k 38k CN101 21 23 86 56k 38k 87 F E F 224k E 48k 224k 56k 9392 D/A 80k 110k TE C211 100pF A/D TE OFFSET TO DIG. EQ 48k R216 27k R215 27k 60k 20k 95 94 TE2 TEC R212 0 C212 6800pF 16k 10k (80k/300k) 20k Fig.4 : FOCUS ERROR AMPLIFIER 224k (56k+27k) 80k 38k CX-938 7) DFCT (Defec

25、t) 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 t

26、he 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

27、 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

28、 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 tr

29、ack : 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 3T CIRCUIT DFCT CIRCUIT BOTTOM DETECT BOTTOM

30、 DETECT PEAK DETECT LPFS/H A/D A/D 76 75 73 3 2 40k 20k 20k 40k 40k 40k 200k 200k C205 0.1F 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)5 Surfac

31、e defects RFI HOLD RFI MIRR OFF TrackON Track 6 CX-938 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

32、scratches or stains on the disc, or vertical asymmetry of the RF due to variations in the discs manufactured cant 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 si

33、gnal. 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 cente

34、ring on REFO. 74 RFI 40k 40k C206 3900pF 72 71 ASY EFM 40k 40k15k75k 2k R205 10k R206 39k C203 0.1F C204 3300pF EFM. SIG Fig.9 : EFM CIRCUIT 7 CX-938 1.2 SERVO SECTION (UPD63710GC : IC201) The servo section controls the operations such as error signal equalizing, in focus, track jump and carriage mo

35、ve. 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 signa

36、l 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 spin

37、dle 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 di

38、agram. 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 a

39、s 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 : 1 The lens approaches the disc from its current position. 2 RFOK = H 3 The FZC signal is

40、 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. FE AMP DIG. EQ 82 A+C B+D FD FOP FOM IC301 BA5986FM LENS IC201 UPD63710GC 85 623 4 14 13 FOCUS SEARCH TRIANGULAR WAVE GENERATOR DACCONTROL A/D R302 15

41、k R301 10k Fig.10 : FOCUS SERVO BLOCK DIAGRAM 8 CX-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 t

42、he 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 be

43、havior by selecting the Display 01 for the focus mode select in the test mode, and then pressing the focus close button. REFO FD LENS POSITION RELATIVE TO DISC NEAR FAR JUST FOCUSED MD REFO Expanding around Just Focused Point REFO RFI FOK FE FZD THRESHOLD LEVEL FZD (INTERNAL SIGNAL) Focus closing wo

44、uld normally take place at these points XSI (IN THE EVENT FOCUS IS CLOSED) LEVEL Fig.11 : FOCUS CLOSE SEQUENCE 9 CX-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 r

45、eceives 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 th

46、e 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 fix

47、ed 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 termi

48、nated 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 11 12 6 7 R304 15k R303 10k TE AMP DIG. EQ 86 F E TD IC201 UPD63710GC

49、87 63 JUMP PARAMETERS DACCONTROL A/D t1 t2 GAIN NORMAL TD KICK BRAKE TEC T. BRAKE EQUALIZER T. SERVO CLOSED OPEN NORMAL GAIN UP OFF ON t1 TD TEC (10 TRACK) EQUALIZER T. BRAKE SERVO SD 2.9mS (4.10 TRACK JUMP) 5.8mS (32 TRACK JUMP) GAIN UP NORMAL ON OFF OPEN CLOSED t2 50mS t Fig.12 : TRACKING SERVO BLOCK DIAGRAM Fig.13 : SINGLE TRACK JUMP Fig.14 : MULTI-TRACK JUMP 10 CX-938 b) Brake Circuit The servo retracting performance can be d