Dokorder-7700-tape-sm维修电路原理图.pdf

DOKORDER rnoder 77OO SERVICE MANUAL sM, 1004-00 1977.3 sEcroN 1 TECHNICAL DESCRIPTION AND ADJUSTMENT PROCEDURES D bokorder, lnc. 5430 ROSECRANS AVENUE, I-WNDALE, CALIF. 90260 U.S.A. r-rE Kr <)JK-YO CO., r-trE). 26.1 1, 3-CHON4E, NISHI-ROKUGO, OTA-KU, TOKYO, JAPAN RadioFans.CN 收音机爱 好者资料库 TABLE OF CONTENTS 1. GENERAL DESCRIPTION 1 1 1 Amplifier Circuitry g 1-2 Tape Transport Mechanism 1-3 Power Supply Circuitry 2. SERVICE DATA 2 21 Mechanical 2-2 Electrical 3. PARTS LOCATION . 3-4 3-1 Outer Parts 3-2 lnner Parts 4. REMOVAL OF OUTER PARTS 5 r 4-1 Front Panel 4-2 Amp Panel 4-3 Top and Bottom Boards ./ 5. ADJUSTMENT -MECHANTCAL- . . 6-11 5-1 Auto Shut-off Switch 5-2 Pinch Roller Drive Mechanism 5-3 Reel Motor Torques 5-4 Brake Mechanism 5-5 Tape Speed 5-6 Wow/Flutter g 6. ADJUSTMENT -ELECTRTCAL- .12-20 6-1 Adjustable Parts Location 6-2 Adjustment Procedures 7. MAINTENANCE . 21 7 -1 Cleaning 7-2 Lubrication 7 3 Demagnetizing y) B. TECHNICAL DESCRIPTION .22-31 8-1 Solenoid Drive Circuit 8-2 Capstan Drive Circuit 9. SCHEMATIC DIAG RAM Note This Service Manual consists of three sections: Section 1: Descriptions of circuitry, operating procedures, and methods of adjustments and maintenance, plus technical data. Section 2: Exploded views, and parts list. Section 3: Patterns, schematics and parts lists for printed Circuit boards. v RadioFans.CN 收音机爱 好者资料库 v v v v 1. GENERAL DESCRIPTION The Dokorder Model 7700 is a -track,2-channel,2-speed tape deck equipped with 3-motor, 3-heacl and sole- noid operation facility. Designed for high dependability and electrical performance. Their features: 1.1 AMPLIFIER CIRCUITRY 1. The convenience features of the 7700s amplifier circuit such as the Monitor Switch. Mic AMp Circuit, Head- phone AMP Circuit and Level Meter AMP Circuit built in. 2. 4-separate controls permit subtle input/output level adjustments. 3 2-stepped Equalizer Switch is equipped to use for the several type of tapes. The relation between the tapes and the position of the switch is illustrated below. 1-2 TAPE TRANSPORT MECHANISM 1. The convenience features of the 7700s tape transport such as the all-electronic operation buttons, pause con- trol, tape travel counter are positive, and the mechanisms themselves are rugged and dependable. 2. fhe tape transport offers an Auto Stop convenience, and when the tape reaches its end in any mode (fast for- ward, rewind, play or record). a solenoid releases the locked operating control (s) to place the deck in the stop mode. 3. High dependability is proven by using newly improved electronic solenoid control system that reduces the powerconsumption and heat up in the solenoid and its control transistors. 4. Especially high speecl-accuracy and surprising wow/fluttel characteristics are realized by using most advanced PLL (Phase-Locked Loop) Servo System in capstan motor drive. 5. Newly designed high-torque outer-rotor eddy-current motor is used for reel drive. 1-3 POWER SUPPLY CIRCUITRY 1. The primary winding of the power transformer is provided two taps 100 V and 54 V. The former is used for the reel motor drive in the fast winding mode. while the latter is used for the reel motor drive in the rec/play mode. 2. On the secondary side, the transformer also offers two windinqs for 5.6 V and 14 V x 2. The former is used for illuminating the pilot lamps, while the latter is rectified and then used to power the amplifiers, solenoid, PLL circuit and capstan motor. Equalizer Switch Type of Tape Normal (button out) Scotch #212 or equivalents Special (button in) Maxell #UD-35 or equivalents v 2. SERVICE DATA 2-1 MECHANICAL Record/Playback System 4 track 2 channel stereophonic Tape Width Standard 1/4 inch tape Reel Size 7-inch or smaller Motor Three (one 2 speed PLL DC servomotor for capstan, two 6 pole induction outer-rotor type for reels) Head Three (1 erase, 1 rbcord, 1 playback) Tape Speed !1 .5o/oat 19 cm/sec (7-1 l2ipsl ,!1 .5%at 9.5 cm/sec (3 3/4 ips) Wow and Flutter Playback (RMS) 0.13o/oat 19 cm/sec (7 112ipsl ,0.20% at 9.5 cm/sec (3-3/4 ips) Fast Winding Time 100 sec for 7-inch reel (1800-foot tape, 60 Hz) Motor Torque Hold-back tention (playback) 85 gr 110 gr (255 t30 g.cm) Take-up torque (playback) 150 gr (450 g.cm) FFlREW hold-back tention 30 gr ( 90 g.cm) Brake Torque 600 - 800 gr (1.8 - 2.4 kg.cm) weight 35 lbs Dimension 17-314 (H) X 16-718 (W) X 6 3/4 (D) 2-2 ELECTRICAL al v Y/ V Equalization Bias Frequency Frequency Response (Playback ) Frequency Response (Overa ll ) One-channel Recording Signal to Noise Ratio Crosstalk Channel Separation Bias Leakage Erase Eficiency Distortion (Overall) Meter Calibration lnput Mic L ine DIN Output Line DIN Circuit Complement Power Consumption Power Requirement Headphone 2mW 8Q NAB 130 KHz +1 KHz .19 cm/sec (7 l12ipsl 50 - 100 Hz l! oa, 1o1 Hz - 1 5 KHz 13 dB o 9.5 cm/sec (3 3/4 ips) 50 Hz - 7.5 KHz 13 dB o 1 9 cm/sec (1-1 12 ips) Normal 30 Hz - 20 KHz t3 dB (30 - 100 Hz, 15 - 20 KHz t5 dB) Special 30 Hz - 20 KHz 13 dB (50 - 100 Hz, 15 - 20 KHz t5 dB) o 9.5 cm/sec (3-3/4 ips) Normal 35 Hz- 12KHz t3dB (35 -1 00 Hz, 1.5- 12 KHz15 dB) Special 35 Hz - 12 KHz 13 dB (35 - 100 Hz, 7.5 - 12 KHz 15 dB) TOOHzll dB, 15 KHz+5dB at 19 cm/sec (71 /2ipsl 500 Hz 11 dB, 7.5 KHz +5 dB at 9.5 cm/sec (3-314 ips) Better than 50 dB (Playback) at 0 dB output level Better than 46 dB (Overall) at 0 dB output level Better than 50 dB at 1 KHz Better than 40 dB at 1 KHz Less than -25 dB Better than 65 dB at 1 KHz Less than 3% at 1 KHz 0 dB output level 0 dB at IOOHz 0 dB output level (P.8. VR-Max) -58 dB 10 KO (load imPedance) -20 dB 220 K9 30 mV 80 KQ OdB 47KQ 260 mV 47 KS) 34 transistors, 29 diodes, 5 lC,2 FET ,2 LED, 1 PUT 75W U.S.A. type 117 V (60 Hz) Universal type 100 V,117V,125V,20OV,220V,24O V (50/60 Hz) Specs are subject to change withor-rt notice. v 3. PARTS LOCATION 3-1 OUTER PARTS v v v Front View 20 Push Button, Metal, EO, Speed, Monitor, Pause SW 21 Push Button, Red, Rec. SW (556-0009-00) 22 Operate Button, Rec. (556-0038-80) 23 Ope. Button, FF then remove the panel itself by moving it as the arrow in the illustration shows. NOTE: When mounting the front panel, reverse the steps described above. Take note that cup washer should be fitted on the two screws securing the bottom part of the front panel. Also, note that conduc- tive rubber washer shoutO be f itted on the screw securing the right side of thefront panel. This is for grounding the front panel. v 4-2 AMP PANEL 1. Withdraw control knobs-RECORD LEVEL CONTROLS and PLAYBACK LEVEL CONTROLS. 2. Remove the two screws (BS-3 X 6) above and (BS-3 X 18) below the level meters by turning them counter- clockwise. Then, remove the four screws (BS-4 X 15) that secure the amp panel. NOTE: Take care not to lose the nylon washer whenremoving the two screws above and below the level meters. 3. When mounting the amp panel, reverse the steps described above NOTE: Fit and tighten the screws only after checking to see that the record indicator LEDs are correctly fitted in the holes on the amp panel and that the level meters are also fitted correctly in the amp panel holes. Take note that the conductive rubber washer should be fitted on the screw that secures the upper right side of the amp panel (see 4-1. 3 above) 4.3 TOP AND BOTTOM BOARDS 1. Remove the six black-painted screws (RS-3 X 6) that secure the top board. 2. To remove the botrom board, remove the four screws RS-3 X i4) securing the two FOOT ASSYS by turning them counterclockwise. Then remove the FOOT ASSYS themselves 3. With the FOOT ASS,YS dismounted, remove the screw (RS-3 X 8) securing the bottom board at its center by turning it counterclockwise, then remove the bottom board itself 4. When mounting the top and bottom boards, take care not to confuse the screws securing the top board with those securing the bottom board; they are different in size and finish. (e) aI F-a Fig.4-1 v 3-2 INNER PARTS *T*- v Front View Back View ffiir:t:rj:. : :- -:;. :. .:.:ii.:l:;.=?: 31 Solenoid, Brake, DC-24V 48 ohm (1 1 6-2002-00) 32 Linkage, Brake (525-0025-00) 33 Stopper, Brake Linkage (528-0008-00) 34 Linkage, Brake Solenoid (525-0027-00) 35 Bracket, Brake (533-0082-00) 36 Guide, Brake Linkage (528-0009-00) 37 Spring, Brake (541-0007-05) 38 Solenoid, Pinch Roller Pressure, DC-24V 15 ohm (1 1 6-2003-00) 39 Spring, Pressure (541-0010-01 ) 40 Arm, Pinch Roller Drive (525-0029-00) 41 Arm, Pinch Roller (525-0032-00) 42 ShaIt, Pinch Roller (521-0025-05) 43 Arm, Auto Shut-Off 825-OO24-O4) 44 Switch, Micro, Auto Shut-Off (131-3001-00) 45 Bearing, Capstan 522-OO1O-O2) 46 Dressing Plate, Tape Lifter (521-0029-00) 4-l Head Base AssY (830-001 1-00) 48 PC Board Assy (PCM-365A), Head Connect (831-0004-00) 49 Tension Arm Assv (Left) (840-0016-00) 50 Tension Arm Assy (Right) (840 001800) 51 Pulley, Motor, No.3 (523-0031-04) 52 Belt, Capstan Drive 1524-OOO7-O2) 53 Belt, Counter Drive 524-0006-00) 54 PC Board Assy (PCM-3978), Rec. * (upcu,a = qls Dressing Plate z ?, a. roctDecrease Fig.5-4 Moror chasis /-i t)- 2, gate N outputs an Nrl number of L pulses to set flip-flop FFg into accele- ration mode. Next, when Nv is Nv ) 2, flip-flops FFz and FFs are reset so that Fv starts decreasing. When Nr ) 2, the FG frequency Fv varies very slowly according to the inertial moment, with the motor rotating at a frequency slightly lower than the synchronization frequency. ln order to avoid setting flip-flop FFs when Nr ) 2 and accelerating the motor, flip-flop FFg is forced to reset by time constant T3 for the period from when the PLL control is started to when Nr = Nv = 1 is established. Nr)2Nvz)2 Acceteration- f ,oo Synchronization Rise Characteristic of Fv (from zero to forced synchronization) B-1 1 3) Speed-up f rom f ine acceleration to synchronization: The PLL mode itself is a sort of acceleration mode, and since Fv is a STOP signal and Fr is a TURN signal, the motor is accelerated more at Fv ( Fr than at Fv = Fr. lt causes the motor to be accelerated gradually at Fv ( Fr, until Fv = Fr, i.e. Nv - Nr = 1, is reached. When this status is reached. the PLL output waveform covers from JUL to J-J-I . Unless the motor is subjected to a heavy torque varia- tion which will place the PLL control out of the output range described above, the motor voltage is controlled within the range from 0 to +B (so long as the phase difference of Fv and Fr stays in the range from 0 to -2n1 . The system is ballanced allowing the motor to rotate in synchronization with the reference frequency F r. Reference Oscil lator Circuit For motor speed control, the reference frequency Fr must be sufficiently stable against the following factors: 1) Voltage fluctuation 2) Thermal variation v 28 ln general, quartz controlled oscillators, CR or LC oscillators and relaxation oscillators are popularly used to regulate speeds. The quartz oscillator oan provide maximum stability but is expensive. For accurate control, the CR oscillator requires very precise and stable CR components, while the LC (tuned) oscillator is not suitable to control audio frequencies. The thermally compensated PUT relaxation oscillator is a practical solution to these prohrlems. 1fl_ 680K 512H2 o.oo39 0.0012 I c 1M 10K lrl PUT OSCVoltage conversion 1 /2 frequencv d ivider Fis. 8-12 ln the above figure, the oscillating frequency is given by: , 1 , i ._, Josc = a* (ln 1_ nl- Substituting for constants, a=ffi=o+ R1 R1+R2 (stand-off ratio) 1 6.8X 10s X 5.1 X 10-e (,# t-t= 544H2 t J osc Max - .fosc Min f rfif -1 = 474H2 Thusthel00kSrpotentiometercanvarytheosciltatingfrequencyintherangefrom4T4HztoS44Hz. - 3 Bridge-type Motor Drive Circuit PLL logic output Slow Blow Fuse Fis.8-14 T -r P resse d Pinch roller R e lea sed Bridge motor circuit Fis. 8-13 i truul Motor vortase waverorm A-n-,f-,/- Motor cu rren t wavef o rm #(a) +(b) Fig. 8-i 7 29 v v v v ln the motor drive circuit above, the PLL logic output operates transistors Or and Oz to control the DC motor. At the same time, there is a bridge circuit composed of resistors Rr, Rz, R: and Ro (DC motor). Resistor Rs is used to sense the motor current, while Rr and Rz are the motor voltage sensing resistors. The balance condition of the bridge, where R1, R3 = Rz, Ro, produces across o and B a counter electomotive force proportional to the motor speed. By supplying this electromotive force to the base-emitter of transistor 01 , a feedback is provided to maintain the motor speed against load variations and power voltage fluctuations. lf +Bz increases, the voltage drop across Oz will increase to keep the motor voltage constant, while the pulse width will also be kept constant (Figs.8 15 and 8-16). The motor is also driven to the rated speed against variations in the load torque, so that sharp rising charac- teristics have been obtained when the pinch roller is pressed, as shown in Fig.8-l7. R.: DC motor current sensing resistor (in a negative feedback loop) Fl , Rr: DC motor terminal voltage sensing resistor (in a positive feedback loop) E(V) Fis.815F iq. 8-1 6 v 30 z o5* F z o$* F oz (9oO o 9 3 s- og Yt 96 .9 ci x: d: r ? f;d eEi edE !F -!d tr ? :; E : er r:9 E-: 5r e6, :aE iFE .o i;- <od, o; ri E.:- :9b veF :o r F o.:c tl :9 !_+ rio,: 90N -.I 93. $E: : e i: r!9 n5 , o i3 -;E 1: :33 !: :i= aE: i: !.: - : lui 5 ;e A;6 *9- 9*9 or =i.s iE; ;da :B .o9 !r: Eq, cr fln 639 9o.r I qbr 43! ,o- <n 919 : P b!9 = ;o ;o! .:; P- o: 66o , o? 9l :rr Jr-o 99- F: i;eEig: B.rF :- ioqE;oJ E+F U3.! _:g - ?cr ro -*Foq:3q :g gF 3E!E; i:.- la e;Eieqb sEi Ep +S5:!; !,; o9 -o9: = !-; r e.9;r=;3 ea. E; .-;f-.*_nn: oord;:p;i E- : -i- 6racd9 - d ? i -!: -6i ? oi o(,o ii: ,i! : lr F tr I (J IJJ F J o tr F z o C) -J J a 6 ( 31