Nakamichi 481 Service Manual
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Nakamichi 481 Service Manual

Nakamichi 481 Service Manual

Diskrete head cassette deck
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Summary of Contents for Nakamichi 481

  • Page 2: Table Of Contents

    CONTENTS 1. General .…………………………………………………………………………………… 3 Principle of Operation ….……………………………………………………………... 4 2. 1. Mechanisms ….……………………………………………………………… 4 2.1.1. Headblock ..……………………………………………………… 4 2.1.2. Erase Head ..……………………………………………………… 5 2.1.3. Double Capstan Tape Drive ………………………………… 5 2.1.4. Mechanism Control Cam Operation ………………………… 6 2. 2. Amp. Circuits ….………………………………………………………………...
  • Page 3 9. 5. Control Switch Holder Ass’y (B02) …………………………………………………………. 43 9. 6. Headphone Jack Ass’y (B03) ………………………………………………………………. 43 9. 7. Mechanism Ass’y 481 (B04) ………………………………………………………………. 44 9. 8. Chassis Ass’y (B05) …………………………………………………………………………. 45 9. 9. Flywheel Holder Ass’y (C01) …………………………………………………………. 45 9.

  • Page 5: Principle Of Operation

    (1) Adjustment of Tape Guide Height Accuracy of tape travel is one of the most essential Tape Guide of the N-481 is assembled into the Take-up factors for a device to optimize its performance. and Supply Pressure Roller Assemblies. With a spring in Inaccurate tape travel will therefore induce deterioration the stud of Mechanism Chassis Ass’y, Pressure Roller...

  • Page 6: Erase Head

    The N-481 employs 2 capstans, each the head base, the pressure rollers have to be evenly having different diameter and rotations, thereby avoiding...

  • Page 7: Mechanism Control Cam Operation

    Refer to Fig. 2.1.6 Mechanism Control Cam timing chart. tape begins to run. If you press the Pause Switch at this Function of N-481 Mechanism is done by Cam Control. stage, it comes to Pause mode. Brake operates and the Cam is driven by the Control Motor.

  • Page 8: Amp. Circuits

    Nakamichi ZX improve frequency response at high. L101 and C186 70us Nakamichi SX, TDK SA, Maxell compose a bias trap circuit and prevent bias leakage from XL-II playback eq. amp. circuit. Scotch Master 70 us Playback eq.
  • Page 9 Cr02. for instance, record and playback on ferric oxide tape with However, in the case of Eq. Switch on N-481, when time putting Tape Switch on EX and Eq. Switch on at 70 us.) constant at playback is changed, at the same time When Nakamichi EX or EXII Tape is used at Tape Switch: constant at record must also be changed.
  • Page 10 2.2.2. Record Equalizer Amplifier Circuit 2.2.3. Bias Oscillation Circuit The record equalizer amplifier circuit consists of the Out Fig. 2.2.5 shows a push-pull oscillator with an oscillation put Amp. incorporated in the Dolby NR IC and peripheral frequency of 105 kHz which is constructed by capacitors circuits as shown in Fig.

  • Page 11: Mechanism Control Circuits

    ON state, as a result, Q402 is Stop Button is of momentary type and acts to release turned ON, the REW signal becomes H, and the N-481 is other buttons mechanically. But it is not used to control set in REW mode.

  • Page 12: 12 V Power Source

    2.3.2. +12 V Power Source Refer to Fig. 2.3.2 circuit diagram. Only +24 V DC power supply is used in the N-481. The circuit acts to produce a +12 V power source from the +24 V DC power supply. Mechanism control is done by using thus produced +12 V.
  • Page 13 (a) Reached tape-end during PLAY (PLAYBACK or a Schmitt circuit which provides hysteresis characteristics RECORD), FF, or REW mode for ON/OFF of Q430. Accordingly, Q430 will be Explanation is made for PLAY mode as an example. For FF turned ON or OFF without chattering for the input waveform or REW mode, the shut-off function is the same as for PLAY with a large time constant developed across C412.
  • Page 14 (b) Mode is changed Switch is turned ON or OFF. During the Power-mute sig From FF to REW mode, or vice versa, or from FF -nal is L, the voltage at the point A becomes lower than to PLAY mode the emitter voltage of Q424.

  • Page 15: Record Control Circuit

    2.3.5. Record Control Circuit play position and stays there, thus the mechanism is set Refer to Fig. 2.3.8 circuit diagram. to RECORD mode. RECORD mode is set by pressing Record Button, then Record circuit is designed to protect from the erroneous Play Button together.

  • Page 16: Control Motor Drive Circuit

    2.3.7. Control Motor Drive Circuit amplifier IC402 (1/2) becomes zero, the control motor Refer to Fig. 2.3.10 circuit diagram and Fig. 2.3.11 timing stops. chart. The control motor is turned by varying amounts, The following table shows the relationship between cam according to which control button is set.

  • Page 18: Reel Motor Governor

    2.3.8. Reel Motor Governor Refer to Fig. 2.3.12 circuit diagram. One end of the reel motor is connected with +12 V and the other end is a terminal for controlling. During FF mode, Q413 is turned ON and the reel motor is grounded. Accordingly, the reel motor turns in the direction of fast-forwarding.

  • Page 19: Removal Procedures

    3. REMOVAL PROCEDURES 3.1. Cassette Case Cover Ass’y Refer to Fig. 3.1. (1) Press the Eject Button to open the Cassette Case Ass’y. (‘2) Pull out F01 (Cassette Case Cover Ass’y) upwardly. 3.2. Top Cover Ass’y Refer to Fig. 3.1. Remove F02 and F03, then disassemble F04 (Top Cover Ass’y).

  • Page 21: Main P.c.b.ass'y

    3.9. Main P.C.B. Ass’y Refer to Fig. 3.3. (1) Refer to Fig. 3.2. Remove Front Panel Ass’y referring to item 3.4. Remove 5 connectors and the wires connected by wrapping from the F05 (Main P.C.B. Ass’y). Remove F01, F02, F03, F04 and the Record Switch Linkage from the Wire Holder assembled with Record Switch, then disassemble F05 (Main P.C.B.

  • Page 23: Cassette Case Ass'y And Cover Plate Ass'y

    3.14. Cassette Case Ass’y and Cover Plate Ass’y Refer to Fig. 3.5. (1) Refer to Fig. 3.2. Remove Mechanism Ass’y referring to item 3.6. (2) Press the Eject Button to open the Cassette Case Ass’y. (3) Remove F01, then disassemble the piston of the Pneumatic Damper Ass’y.

  • Page 24: Capstan Motor Ass'y And Flywheel Ass'y

    3.16. Capstan Motor Ass’y and Flywheel Ass’y Refer to Fig. 3.6. (1) Refer to Fig. 3.2. Remove Mechanism Ass’y referring to item 3.6. (2) Remove F01 and F02, then disassemble F03 (Fly wheel Holder Ass’y) and F08 (Capstan Belt). (3) Remove F04, then disassemble F05 (Capstan Motor Ass’y). (4) Remove F06, then disassemble F07 (Control P.C.B.

  • Page 25: Cam Drive Gear And Control Cam

    3.21. Cam Drive Gear and Control Cam 3.23. Pressure Roller Ass’y and Erase Head Refer to Fig. 3.8. Refer to Fig. 3.7. (1) Remove Sub Mechanism Chassis Ass’y referring to (1) Remove Head Mount Base Ass’y referring to item 3.22. item 3.17.

  • Page 26: Measurement Instruments

    (27) Audio Analyzer T-1 00 (including Distortion, Wow/Flutter, Speed, Oscillator and dB meter) Notes: 1. (10) — (27) are the products of Nakamichi Corporation. 2. EH Stroke Check Gauge M-9042 (DA09042A) should be used for the Models from serial Nos. A30601001 to A30604798, and EH Stroke Check Gauge M-9051 (DA09O51A) is for the Models bearing serial Nos.

  • Page 27: Mechanical Adjustments

    Therefore to keep the VR603 (for Cam position play) Cam at the record position, following procedure (b) Press the Stop Switch to set the N-481 in stop mode. is required: Adjust VR602 (for stop) so that the “S” mark on the Short the both leads of capacitor C406 (2.2 uF) on the Main P.C.B.

  • Page 28: Tape Speed Adjustment

    9.5 V (±0.3 V) when mute is released (mute signal necessary. changes from H to L). Set the N-481 in FF mode, then adjust the value of (This voltage is determined by the adjustment of R436 R414 so that the voltage of VR601 will become lower by in above step (c).)

  • Page 29: Record Head And Playback Head Tilt Adjustment

    (A). Record Head “Upper” or “Lower” are illuminating. In (8) Set the N-481 in stop mode and fit both of the ser rated order not to give damages onto the head surfaces, height gears. Then set the N-481 again in play mode push both of slide knobs of the Gauge to the direction of and insure all of the 4 Beacons are illuminating.

  • Page 30: Tape Guides Adjustment And Erase Head Stroke Adjustment

    Bar is accepted by the take-up tape guide. the supply tape guide, thus check can be made on (e) If the above are insured, set the N-481 in pause mode, supply tape guide height. then in play mode to see whether adjustments are (d) If the supply tape guide is misaligned, the Supply Tape appropriately made.

  • Page 31: Erase Head Height And Tilt Adjustment

    N481. (8) After completion of adjustment, 3 pcs. of screws shall (3) Set the N-481 in stop mode. be locked with lock tight paint (4) Check to insure whether one of the 3 Beacons is Note: Before use of this gauge, check to insure freedom illuminating.

  • Page 32: Playback Head And Record Head Height Adjustment And Azimuth Alignment

    (a) Connect a VTVM to the Output Jacks. (b) Load a Reference SX Tape (DA09025A). Set the Eq. and Tape Switches of the N-481 to 70 ps and SX positions, then set the N-481 in record and play mode. (c) Feed in 400 Hz (0 dB), then turn the RH Height Gear until the output of both channels becomes maximum.

  • Page 33: Record Head Stroke Adjustment

    5.8. Record Head Stroke Adjustment Readjustment of Record Head Mounting Gauge Refer to Figs 5.14 and 5.15. M-9048 (DA09048A) Note: This adjustment will be required only to insure Mount the Block B onto the Mounting Gauge Plate. freedom from misalignment of the record head Loosen the 2 screws fixing the Block A.

  • Page 34: Tape Travelling Adjustment

    Release the back-tension (rotate the Supply Reel and (3) Set the N-481 in record and pause mode. feed out some length of tape) and set the N-481 in play Check to insure that the gap between the top of the wire mode.

  • Page 35: Flywheel Holder Adjustment

    Fig. 5.19.2. (3) Tighten the screw, then apply a quantity of lock tight paint. 5.13. Lubrication N-481 is a lubrication-free cassette deck except when parts are replaced. Apply the following lubricant for each replaced part: (1) LAUNA#100 Capstan Shaft...

  • Page 36: Parts Location For Electrical Adjustment

    PARTS LOCATION FOR ELECTRICAL ADJUSTMENT...

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