JVC-KDA77-tape-sm维修电路原理图.pdf

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1、JVC MODEL KD-A77 A/B/C/E/J/U STEREO CASSETTE DECK No. 4186 September 1979 RadioFans.CN 收音机爱 好者资料库 KD-A77A/8/C/E/J/U r- Contents Specifications . 2 Features . 3 Controls and Connections . 3 Main Parts Location . 4 Maintenance . 4 New Technique . 5 Removal of the Main Parts . 6 Main Adjustments . 1 0

2、Block Diagram . 16 Integrant Circuit . 18 Standard Schematic Diagram of KD-A 77 Amplifier circuit . 1 9 Mecha. control circuit . 20 Wiring Connection (1 ) of KD-A 7 7 . 21 Specifications Type Track system Tape speed Frequency response OVU Metal tape SA/Cr02 tape -20VU Metal tape SA/Cr02 tape * 1 *2

3、SF/Normal tape * 3 SIN ratio Stereo cassette deck 4-track, 2-channel 1-7/8 inch/sec (4.8 cm/sec) 25-12500Hz 3dB(Typical) 25 -8000Hz 3dB(Typical) 15-20000Hz 25 -1 8000Hz 3dB(Typical) 15-20000Hz 25-1 8000Hz 3dB(Typical) 15-19000Hz 25-17000Hz 3dB(Typical) Surpases DIN 45 500 60dB (from peak level, weig

4、hted, Metal tape) The SIN is improved by 5dB at 1 kHz and by 10dB above 5kHz with ANRS on. (DIN 45 500 weighted) Effect of Super ANRS : (normal tape) Improvement of SIN : the same as with ANRS Improvement of frequency response : OVU recording; 6dB at 10kHz + 5VU recording; 12dB at 10kHz Improvement

5、of distortion Wow and flutter Crosstalk Hormonic distortion Bias Erasure Heads No.4186 OVU recording; 3 % or less at 10kHz + 5VU recoridng; 3 % or less at 10kHz 0.04% (WRMS), 0.14% (DIN 45 500) 65dB (1 kHz) K3; 0.4%, THD: 1.0% (metal tape, 1 kHz OVU) AC bias (85kHz) AC erasure (85kHz) 3 heads SEN AL

6、LOY head for recording, SEN ALLOY X cut type for playback and two-gap SEN ALLOY head for erasure Wiring Connection (2) of KD-A77 . 22 Enclosure Assy and Electrical Parts . 25 Enclosure Assy and Electrical Parts List . 23 Mechanical Components Parts . 26 Mechanical Components Parts List . 28 Printed

7、Wiring Board Parts Main Amp. P.W. Board Parts . 33 Power Supply P.W. Board Parts . 34 Main Amp. P. W.B Parts List . 30 Power Supply P.W.B Parts List . 35 Other P.W.B Parts . 37 Other P. W.B Parts List . 39 Packing . Back cover Accessories . Back cover Motors Fast forward time Rewind time Semiconduct

8、ors Input terminals Output terminals Power requirement Power consumption Dimensions Weight FG type DC servo motor (for Capstan) DC motor (for Reel) 85 sec. with C-60 cassette 85 sec. with C-60 cassette 1 8 ICs, 49 transistors, 59 diodes, 14 LEDs Mic jack x 2, Max. sensitivity; 0.2mV (-72dBs) Matchin

9、g impedance; 6000-10kO Input jack x 2, Min. input level; 80mV (-20dBs) Input impedance; 100kO Output jack x 2, Output level; 0-300mV Output impedance; 6kO Matching impedance: 50kO or more Phones jack x 1, Output level; 0-0.5mW/SO Matching impedance: 80-1 kO AC 120V, 60Hz (KD-AnCW AC 240/220/120V, 50

10、/60Z (KD-A n A/B/E) AC 240/220/120/1 OOV, 50/60Hz (KD-A77U) 36W 17-3/4 (450 mm) W 4-3/4 (120 mm) H 12-7/16 (316mm)D 18.3 Ibs (8.3 kg) Note: * 1 . SCOTCH MET AFINE or Equivalent * 2 . TDK SA or Equivalent * 3 . MAXELL UD or Equivalent Design and specifications are subject to change without notice. -2

11、 - RadioFans.CN 收音机爱 好者资料库 Features 1. 3 SA (SEN-ALLOY) heads Combined SA (SEN-ALLOY) record/play (X-cut type) heads make possible record monitoring. The erase head is a 2-gap head also made from SA (SEN-ALLOY). 2. Two-motor ID (independent Drive) mechanism This mechanism incorporates a newly develo

12、ped Back Tension system which gives improved tape contact with the head. 3. Self-illuminated buttons for full logic mechanical operation (excluding STOP or REC-MUTE modes.) 4. Three position Metal-Tape-Compatible tape select switch. METAL -FeCr _ SA/Cr02 NORM (Automatic switching between SA/Cr02 and

13、 NORM) 5. The REC MUTE button is at the right side of the mechanical operation buttons. KD-An A/B/C/E/J/U 6. ANRS which reduces tape hiss to an inaudible level and Super ANRS which improves linearity at high fre- quencies are incorporated. 7. MEMORY/AUTO REW switch 8. Recording equalizer switch 9. T

14、imer standby capability for automatic recording or playback using an AC timer. 10. Geared and oil-damped cassette holder. 11. New Metal-Tape-Compatible multi-peak level in- dicators (+ 9dB, + 6dB, + 3dB, -2dB, -7dB). together with back-lit VU meters with the expanded coverage from + 7VU to -20VU, ma

15、ke level observa- tion easier. 12. OUTPUT volume (for LINE and HEADPHONES use) 13. Remote control terminal (for the optional remote con- trol unit -R-30E). Controls and Connections 2 3 4 5 6 10 11 12 14 15 16 17 18 19 20 21 = = = = = = = = = = r-= . . = - 1. VU meters and Multi-point peak level indi

16、cators 2. INPUT LEVEL control 3. TAPE indicators 4. ANRS/Super ANRS indicators 5. Cassette holder 6. MEMORY/AUTO REW switch 7. Tape counter/counter reset button 8. EJECT button 9. TIMER STANDBY switch 10. PHONES jack 11. MIC jacks 12. INPUT SELECT switch 13. ANRS switch 14. TAPE SELECT switch 15. RE

17、C EQ switch 1 6. OUTPUT LEVEL control n LJ 22 23 24 f r:f 1 r - I 1 7. MONITOR switch 1 8. Cassette Operation buttons REW (rewind) button FF (fast forward) button PLA Y button STOP button o REC (record) button 11 PAUSE button REC MUTE button 19. POWER switch 20. Power cord 21. Voltage select switch

18、(KD-A 77 A/B/E/U) 22. REMOTE CONTROL socket 23. LINE IN (REC) terminals 24. LINE OUT (PLAY) terminals -3 -No.4186 KD-A77 A/B/C/E/J/U Main Parts Location 2 3 4 5 6 7 9 -8 1 1 1 2 1 3 (Mechanical parts) 1. Front panel assembly 1. Switch holder (U 2. DC solenoid for playback 2. Supply reel assy 3. Reel

19、 motor 3. Idler assy 4. Geared and oil-damped brake assy 4. Reel motor assy 5. Variable resistor (INPUT LEVEL control) 5. Take-up reel assy 6. Meter cover 6. Switch holder (R) 7. LED P.W. Board assy 7. Connecting wire (for play solenoid) 8. Hall element P.W. Board assy 8. Capstan 9. Power switch 9.

20、Slide base assy 10. Power transformer 10. Stad with pad (for back tension) 11. Remote control socket (DIN socket) 11. Erase head 12. Pin jacks assy 12. Combined SA (SEN-ALLOY) record/play heads 13. Mecha. control P.W. Board assy 13. Pinch roller assy Other mechanical parts are the same as location o

21、f model KD-A6: Please refer to the service manual 0 KD-A6 A/B/C/E/J/U (No. 4179 -page 4). Maintenance To get long, trouble-free service, maintenance is important. Do not forget cleaning and demagnetizing. Cleaning After long, the heads and tape part -capstan, pinch roller, etc. -will become dirty wi

22、th dust or magnetize particles. Dirty heads cause imperfect erasing or high frequency drop-off. A dirty capstan and pinch roller will cause unstable tape speed, leading to increased wow and flutter. Always keep them clean by following the procedure below. 1. Heads 1) Push the EJECT button to open th

23、e cassette holder. 2) Push up the transparent cover to remove it. 3) Use the head cleaning stick to wipe the surface where the tape comes into contact with the head. (it is effective to moisten the cotton with alcohol.) 2. Pinch roller and capstan Close the cassette holder with its transparent cover

24、 remov- ed. Press the tape detection pin inside the cassette com- partment and set the deck in the playback mode. Insert the cleaning stick into the hole on the right side at the bottom of the cassette holder and clean the pinch roller and oopan. :,h , . Cleaning stick No. 4186 -4 - 3. Cleaning the

25、cabinet and panel Wipe the cabinet and panel clean with a soft cloth dipped in a neutral cleaner. Do not use thinner, benzine, alcohol or other strong solvents, as these will cause damage to the surface finish of the cabient and panel. Demagnetizing The heads are made from a material resistant to ma

26、gnetiza- tion, but after long use they may become magnetized. A magnet brought into their vicinity can magnetize the heads, causing excess noise. If noise seems to have inceased, demagnetize the heads with a head demagnetizer through the following procedure. 1. Turn the POWER switch OFF. 2. Wrap the

27、 tip of the demagnetizer with vinyl tape of soft cloth so as not to damage the head surface. Switch on the demagnetizer and bring it close to the head. 3. Move the tip of the demagnetizer slowly first to the left and right, then up and down in front of the head. Gradually move it away from the head

28、and switch it off at a distance of more than 30 cm (1 2). 4. The erase head need not be demagnetized. The capstan shaft and tape guide should be demagnetized in the same way as the record/playback head. * Do not bring a magnetized metallic object (a screwdriver for example) near the head as this wil

29、l increase noise. Oiling Feed one or two drops of machine oil to pinch roller shaft once or twice a year under normal conditions of use. Avoid oiling them excessively, or rotation may become ir- regular because of oil splashes. New Technique Combination SA heads for recording and playback (Fig. Al D

30、ue to its high recording density, Metal Tape requires recording and playback heads that are made of materials having a greater maximum magnetic flux density than con- ventional ferrite or permalloy. The combined record/playback heads, newly developed for the KD-A 77, both employ SA (Sen-Alloy) to en

31、sure high performance. The SA head has advantages over conventional heads in various fields such as fewer core loss, greater gap ac- curacy, better wear and corrosion resistance. However, its biggest feature is its high maximum magnetic flux densi- ty. Because of this, the SA head can bring the most

32、 out of the superior performance of Metal Tape. This is especially true for its extended frequency response at high frequen- cies; something that has never been possible to realize with usual cassette tapes. The playback head incorporates a unique X-cut core struc- ture to improve the characteristic

33、s of the low frequency range. With ordinary core configurations, playback output is subject to peaks and dips in the low frequency range as shown in Fig. B. This is called the contour effect. :this effect is caused by interference between the length of the tape-to-head contact area and the wavelengt

34、h of the recor- ding frequency. With the X-cut design the core is cut diagonally to enable the tape to leave the head, not abrupt- ly, but with a gradually lessening contact area. The result is, as shown in the diagram, reduction of the contour effect. (Fig. C) Configuration of record/playback combi

35、nation SA heads CD SA recording head 4/lm gaps 1/lm gaps Fig. A X-cut SA playback head SA chips Shield plate rJ) Zinc die-casting head base -5 - KD-A77 A/B/C/E/J/U Comparison between characteristics of conventional cut core and X-cut core c onventlona I h d . h ea Wit standard core constructi on in

36、-. QJ . :J B- :J 0 -11 16 10 I :J / / /,1./ Usign standard curre / I I I I I , nt recorded tape 10 .0 70 100 100 .00 Frequence (Hz) Fig. B X -cut core construction in :9 a; . :J Cl. . :J 0 11 16 10 t-off-+ Using standard current recorded tape I I I 10 .0 70 100 100 .00 Frequence (Hz) Fig. C Note: SA

37、 (Sen-Alloy) is a trademark of JVC. No.4186 KD-An A/B/C/E/J/U Removal of the Main Parts This cassette deck which features a compact design and high performance uses miniature sized parts which are closely ar- ranged. Take special care when servicing it. .11 Q -. ;:;.;.f=. Lever knobs Screws (Top vie

38、w) Screws (Bottom view) Screw Screws Screw l Enclosure assembly 1 . Cassette door . Push the EJECT button to open the cassette door. Slide it upwards (approx. 5 mm) to unlock its pawls, and remove it to frontward. 2. Lever knobs (INPUT SELECT, ANRS, TAPE SELECT, MONITOR) and level control knobs (INP

39、UT LEVEL -L and R, OUTPUT LEVEL and REC EQ) Pull them to frontward 3. Top cover . Remove 6 screws fastening the top cover. 4. Bottom cover Remove 7 screws fastening the bottom cover. 5. Front plate assembly 1) Remove 5 screws (3 screws on upper side and 2 screws on bottom side) fastening the front p

40、late assembly 2) Remove TAPE 50 -20kHz and output OdB with impedance 600fl) 3) Attenuator 4) Standard tapes for RECIPB Maxell UD -SF tape (for normal) TDK SA -SA tape (for Cr02) or equivalent SCOTCH MET AFINE -Metal tape 5) Reference tapes for playback (JVC Test Tape) VTT-658 (for head azimuth adj.)

41、 VTT-656 (for motor speed, wow flutter adj.) VTT-664 (for Reference level 1 kHz) TMT-6002N (for playback frequency response) 6) Resistors 1 oon (for measurement of the bias current) 600n (for attenuator matching) 2. Mechanical adjustment 1) Gauge for checking the head position. 2) Torque gauge. 3) B

42、lank tape (C-120) for tape running checker. 11 Mechanical adjustment Head adjustment KO-A77 Back-tension pad Pad (attached to the cassette) Tape Clearance (A) 1. After installing the specified parts in the appropriate positions: A. Snug screw CD gently, then back off about two turns. This makes the

43、heads nearly horizontal. B. Snug screw gently, then back off about one turn. This will roughly position the tape in the center of the tape path. For tightening screw use a home make screwdriver, filed down to the specifications shown below. The same screwdriver can be used to tighten screw (1). Scre

44、wdriver Pinch roller Combination head 2. Make sure that the moving part of the erase head assembly moves smoothly around the pivot of screw and also confirm that there is enough clearance (A) in the play mode. 3. Next, make an operational adjustment. Load a C-1 20 cassette and adjust the height of t

45、he erase head by turn- ing screw . Watching that the tape does not curl at the guides of both the combination and erase heads is indication of proper adjustment. Correct -1 Tape guide t -Tape Incorrect f Tap guide -, Tape guide Tape l _ _-Tape No.4186 -10 - KD-A77 A/B/C/E/J/U Item Adjustment Adjusting Standard Remarks point value Adjusting Connect a speed meter to the LINE Semi-3000Hz If the speed meter functions as a wow motor speed OUT terminals