JVC-MXG75V-cs-sm维修电路原理图.pdf

SERVICE MANUAL COMPACT COMPONENT SYSTEM No.21026 Sep. 2001 COPYRIGHT 2001 VICTOR COMPANY OF JAPAN, LTD. MX-GT98V/MX-GT95V MX-GT88V/MX-GT85V MX-G78V/MX-G75V Safety precautions Important for laser products Preventing static electricity Disassembly method Adjustment method 1-2 1-3 1-4 1-5 1-29 Flow of functional operation until TOC read Maintenance of laser pickup Replacement of laser pickup Description of major ICs 1-33 1-34 1-34 1-3549 Contents (No MIC jack and MIC LEVEL volume for UN ver.) MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V COMPACT DIGITAL VIDEO COMPACT DIGITAL AUDIO Area suffix US - Singapore UN -Asean SP-MXGT98V SP-MXGT95V SP-MXGT98V SP-MXGT95V CA-MXGT98V CA-MXGT95V RadioFans.CN 收音机爱 好者资料库 MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-2 1. This design of this product contains special hardware and many circuits and components specially for safety purposes. For continued protection, no changes should be made to the original design unless authorized in writing by the manufacturer. Replacement parts must be identical to those used in the original circuits. Services should be performed by qualified personnel only. 2. Alterations of the design or circuitry of the product should not be made. Any design alterations of the product should not be made. Any design alterations or additions will void the manufacturers warranty and will further relieve the manufacture of responsibility for personal injury or property damage resulting therefrom. 3. Many electrical and mechanical parts in the products have special safety-related characteristics. These characteristics are often not evident from visual inspection nor can the protection afforded by them necessarily be obtained by using replacement components rated for higher voltage, wattage, etc. Replacement parts which have these special safety characteristics are identified in the Parts List of Service Manual. Electrical components having such features are identified by shading on the schematics and by ( ) on the Parts List in the Service Manual. The use of a substitute replacement which does not have the same safety characteristics as the recommended replacement parts shown in the Parts List of Service Manual may create shock, fire, or other hazards. 4. The leads in the products are routed and dressed with ties, clamps, tubings, barriers and the like to be separated from live parts, high temperature parts, moving parts and/or sharp edges for the prevention of electric shock and fire hazard. When service is required, the original lead routing and dress should be observed, and it should be confirmed that they have been returned to normal, after re-assembling. 5. Leakage current check (Electrical shock hazard testing) After re-assembling the product, always perform an isolation check on the exposed metal parts of the product (antenna terminals, knobs, metal cabinet, screw heads, headphone jack, control shafts, etc.) to be sure the product is safe to operate without danger of electrical shock. Do not use a line isolation transformer during this check. Plug the AC line cord directly into the AC outlet. Using a Leakage Current Tester, measure the leakage current from each exposed metal parts of the cabinet, particularly any exposed metal part having a return path to the chassis, to a known good earth ground. Any leakage current must not exceed 0.5mA AC (r.m.s.). Alternate check method Plug the AC line cord directly into the AC outlet. Use an AC voltmeter having, 1,000 ohms per volt or more sensitivity in the following manner. Connect a 1,500 10W resistor paralleled by a 0.15 F AC-type capacitor between an exposed metal part and a known good earth ground. Measure the AC voltage across the resistor with the AC voltmeter. Move the resistor connection to each exposed metal part, particularly any exposed metal part having a return path to the chassis, and measure the AC voltage across the resistor. Now, reverse the plug in the AC outlet and repeat each measurement. Voltage measured any must not exceed 0.75 V AC (r.m.s.). This corresponds to 0.5 mA AC (r.m.s.). 1. This equipment has been designed and manufactured to meet international safety standards. 2. It is the legal responsibility of the repairer to ensure that these safety standards are maintained. 3. Repairs must be made in accordance with the relevant safety standards. 4. It is essential that safety critical components are replaced by approved parts. 5. If mains voltage selector is provided, check setting for local voltage. Good earth ground Place this probe on each exposed metal part. AC VOLTMETER (Having 1000 ohms/volts, or more sensitivity) 1500 10W 0.15 F AC TYPE ! Burrs formed during molding may be left over on some parts of the chassis. Therefore, pay attention to such burrs in the case of preforming repair of this system. In regard with component parts appearing on the silk-screen printed side (parts side) of the PWB diagrams, the parts that are printed over with black such as the resistor ( ), diode ( ) and ICP ( ) or identified by the mark nearby are critical for safety. When replacing them, be sure to use the parts of the same type and rating as specified by the manufacturer. (Except the J TW2111A, Reverse ; TW2121A Fast Forward and Rewind ; TW2231A 9. Test disc : CTS-1000(12cm),GRG-1211(8cm) 10. Jitter meter MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-30 Arrangement of adjusting positions Cassette mechanism section (Mechanism A section)Cassette mechanism section (Back side) Cassette Mechanism Unit Section Head azimuth adjusting screw (Forward side) Head azimuth adjusting screw (Reverse side) Head azimuth adjusting screw (Forward side) Head azimuth adjusting screw (Reverse side) Playback head Playback, recording and eraser heads or playback head Tape speed ADJ Bias ADJ L Bias ADJ R MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-31 1.Playback the test tape VT703L. 2.With the playback mechanism or recording & playback mechanism, adjust the head azimuth screw so that the forward and reverse output levels become maximum.After adjustment,lock the head azimuth at least by half a turn. 3.In either case,this adjustment should be performed in both the forward and reverse directions with the head azimuth screw. Adjust VR301 so that the frequency counter reading becomes 3,000Hz 60Hz when playing back the test tape VT712(3kHz)with the playback mechanism or playback and recording mechanism after ending forward winding of the tape. Confirmation of head angle Confirmation of tape speed Test tape :VT7036L Measurement output terminal :Speaker terminal Speaker R (Load resistor:6 ) :Headphone terminal Test tape :VT712(3kHz) Measurement output terminal :Headphone terminal Maximum output Tape speed of decks (A and B) :3,000Hz 60Hz Adjust the head azimuth screw only when the head has been changed. VR301 ItemsMeasurement conditions Measurement method Standard values Adjusting positions Tape recorder section ItemsMeasurement conditions Measurement method Standard values Adjusting positions After setting to the double speed motor, confirm that the frequency counter reading becomes 4,800+400/-300Hz when the test tape VT712 (3kHz) has been play back with the playback mechanism. When the test tape VT712(3kHz) has been played back with the playback mechanism or recording and playback mechanism at the beginning of forward winding, the frequency counter reading of the difference between both of the mechanisms should be 6.0Hz or less. When the test tape VT712(3kHz) has been played back with the playback mechanism or recording and playback mechanism at the beginning of forward winding the frequency counter reading of wow & flutter should be 0.25% or less(WRMS). Double tape speed Difference between the forward and reverse speed. P.mecha and R/P mecha speed Wow & flutter Test tape :VT712(3kHz) Measurement output terminal :Speaker terminal Speaker R (Load resistance:6 ) measurement output terminal :Headphone terminal Test tape :VT712(3kHz) Measurement output terminal :Headphone terminal 4,800+400/ -300Hz 60Hz or less with in 0.25% JIS(WTD) Playback mechanism side Both the playback and recording & playback mechanism Both the playback and recording & playback mechanism Reference values for confirmation items MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-32 ItemsMeasurement conditions Measurement method Standard values Adjusting positions 1.With the recording and playback mechanism, load the test tapes(AC-225 to TYP ),and set the mechanism to the recording and pausing conditions in advance. 2.After connecting 100 in series to the recorder head,measure the bias current with a valve voltmeter at both of the terminals. 3.After resetting the PAUSE mode,start recording. At this time,adjust VR101 for LcH and VR201 for RcH so that the recording bias current values become 4.0 A (TYP ). 1.With the recording and playback mechanism,load the test tape(AC-225 to TYP ),and set the mechanism to the recording and pausing condition in advance. 2.While repetitively inputting the reference frequency signal of 1kHz and 10kHz from OSC IN, record and playback the test tape. 3.While recording and playing back the test tape in TYP ,adjust VR101 for LcH and VR201 for RcH so that the output deviation between 1kHz and 10kHz becomes -1dB 2dB. Adjustment of recording bias current (Reference value) Adjustment of recording and playback frequency characteristics *Mode : Forward or reverse mode *Recording mode *Test tape : AC-225 Measurement output terminal :Both recording and headphone terminals Reference frequency :1kHz and 10kHz (REF:-20dB) Test tape :TYP AC-225 Measurement input terminal :OSC IN AC-225 :4.20 A Output deviation between 1kHz and 10kH :-1dB 2dB LcH :VR101 RcH :VR201 LcH :VR101 RcH :VR201 Electrical performance ItemsMeasurement conditions Measurement method Standard values Adjusting positions 1.While changing over to and from BIAS 1 and 2, confirm that the frequency is changed. 2.With the recording and playback mechanism. load the test tape (AC-225 to TYP ),and set the mechanism to the recording and pausing conditions in advance. 3.Confirm that the BIAS TP frequency on the P.C.board is 100kHz 6kHz. 1.With the recording and playback mechanism, load the test tapes(AC-225 to TYP ),and set the mechanism to the recording and pausing condition in advance. 2.After setting to the recording conditions,connect 1M in series to the eraser head on the recording and playback mechanism side,and measure the eraser current from both of the eraser terminal. Recording bias frequency Eraser current (Reference value) *Recording and playback side forward or reverse *Test tape :TYP AC-225 *Measurement terminal BIAS TP on P.C.board *Recording and playback side forward or reverse *Recording mode *Test tape :AC-225 Measurement terminal Both of the eraser head 100kHz +9kHz -7kHz TYP :75mA Reference values for electrical function confirmation items MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-33 Flow of functional operation until TOC read Slider turns REST SW ON. Automatic tuning of TE offset Laser ON Detection of disc Automatic measurement of Focus S-curve amplitude Automatic tuning of Focus offset Disc is rotated Focus servo ON (Tracking servo ON) Automatic tuning of Tracking error balance Automatic measurement of Tracking error amplitude Automatic tuning of Focus error balance Disc to be braked to stop Tracking servo on states Tracking servo off states Disc states to rotate TOC reading finishes Automatic measurement of TE amplitude and automatic tuning of TE balance 500mv/div 2ms/divFig.1 Approx.3sec pin 25 of IC601(TE) Approx 1.8V VREF Tracking error waveform at TOC reading Power ON Play Key Confirm that the Focus error S-cuve signal at the pin28 of IC651 is approx.2Vp-p Confirm that the signal from pin24 IC651 is 0V as a accelerated pulse during approx.400ms. Confirm the waveform of the Tracking error signal. at the pin 25 of IC601 (R604) (See fig-1) Automatic tuning of Focus error gain Automatic tuning of Tracking error gain TOC reading Play a disc Confirm the eys-pattern at the lead of TP1 Confirm that the voltage at the pin5 of CN801 is HLH. Check Point Check that the voltage at the pin40 of IC651 is + 5V? MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-34 Turn off the power switch and, disconnect the power cord from the ac outlet. Replace the pickup with a normal one.(Refer to Pickup Removal on the previous page) Plug the power cord in, and turn the power on. At this time, check that the laser emits for about 3seconds and the objective lens moves up and down. Note: Do not observe the laser beam directly. Play a disc. Check the eye-pattern at TP1. Finish. Maintenance of laser pickup (1) Cleaning the pick up lens Before you replace the pick up, please try to clean the lens with a alcohol soaked cotton swab. (2) Life of the laser diode When the life of the laser diode has expired, the following symptoms will appear. 1. The level of RF output (EFM output : ampli tude of eye pattern) will below. Is the level of RFOUT under 1.25V 0.22Vp-p? Replace it. NO YES O.K (3) Semi-fixed resistor on the APC PC board The semi-fixed resistor on the APC printed circuit board which is attached to the pickup is used to adjust the laser power. Since this adjustment should be performed to match the characteristics of the whole optical block, do not touch the semi-fixed resistor. If the laser power is lower than the specified value, the laser diode is almost worn out, and the laser pickup should be replaced. If the semi-fixed resistor is adjusted while the pickup is functioning normally, the laser pickup may be damaged due to excessive current. Replacement of laser pickup MX-GT98V/MX-GT95V/MX-GT88V MX-GT85V/MX-G78V/MX-G75V 1-35 1 2 3456789 1011 12 13141516171819 2021 22 23 24 AMP Pre Source CTRL AMP ALC ALC AMP AMP EQ CTRL ALC REPPLE REJ Pre Pre L1 L2 R1R2NF2 NF1OUT1 OUT2 EQ1 EQ2 CTL2 CTL1 RIN2 RIN1 RNF2 RNF1 ROUT2 ROUT1 LCLPFGND EQ CTLRFVCC AN7345K (IC302) : PB/REC amp. 2. Pin Function Pin No. SymbolI/O Function FunctionI/OSymbol Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 I I 16 17 18 19 20 21 22 23 24I I O I I Playback amplifier output I I I RIN1 OUT1 1. Block diagram Playback amplifier inputR1 R2IPlayback amplifier input NF2Playback amplifier negative feedback OUT2Playback amplifier output EQ2IEqulaizer CTL2IPre Amplifier input swithing time constant RIN2IRecording amplifier input RNF2IRecording amplifier negative feedback ROUT2 O Recording amplifier outputO LCIALC low cut LPF IALC low pass filter GNDI VccPower supply RFIRepple filter EQCTLEQ control ROUT1ORecording amplifier output RNF1Recording amplifier negative feedback IRecording amplifier input CTL1Pre amplifier input swithing control EQ1Equlayzer Playback amplifier negative feedback NF1 L2I L1 Playbac