Nakamichi 481 Service Manual - page 28

ference voltage in Fast (FF or REW) mode is 

changed. Therefore, re-check of the reference 

voltage in Fast (FF or REW) mode is required. If 

the reference voltage is out of the range, re 

adjustment of R414 according to next step 2) is 

necessary. 

2)  Set the N-481 in FF mode, then adjust the value of 

R414 so that the voltage of VR601 will become lower by 

1.5 V (±0.25 V) than in stop mode. 

3)  Press the Pause Switch to set the N-481 in pause 

mode. 

Adjust the value of R454 to obtain 10 V (+0.4, -0.15 V) 

at the sliding contact of VR601. 

4)  Set the N-481 in playback mode, then adjust the value 

of R453 so that the voltage of VR601 will be come lower 

by 2.5 V (±0.4 V) than in pause mode. 

5)  Short the both leads of capacitor C406 with a jumper 

wire. 

Set the N-481 in record mode, then adjust the value of 

R419 so that the voltage of VR601 will become higher 

by 1 V (+0.4, —0.2 V) than in stop mode. 

Note:  Remove the short of C406 after completion of 

adjustment. 

(3) Cam Timing Adjustment 

(a)  Remove the wires from the Control Motor terminals to 

set the motor open. 

(b)  Without loading a cassette tape and with pressing the 

record protecting switch with your finger tip, press the 

Record and Play Switches to set the N-481 in record 

mode. 

(c)  Turn the Cam and bring the “PY” mark toward the 

pointer by hand. 

Reel Motor will rotate before the “PY” mark reaches the 

pointer. 

Adjust the value of R436 so that the voltage at the 

sliding contact of VR601 becomes 9.7 V (±0.3 V)

 when 

Reel Motor starts rotation. 

(d)  Observe the mute signal at the Q416 collector. 

Turn the Cam referring to above step (c) and check to 

insure that the voltage at the sliding contact of VR601 is 

9.5 V (±0.3 V) when mute is released (mute signal 

changes from H to L). 

(This voltage is determined by the adjustment of R436 

in above step (c).) 

(e)  Observe the (Play + Pause)—Position signal at the 

Q411 collector. 

Turn the Cam referring to above step 

(c) and adjust 

the value of R432 to obtain 11.2 V (±0.4 V) at the 

sliding contact of VR601 when (Play + Pause) — 

Position signal changes from L to H (bias oscillation will 

begin). 

(f)  Upon completion of above adjustment, re-connect 

wires to the motor terminals. 

5.2. Tape Speed Adjustment 

(1)  Remove the Top Cover. 

(2)  Connect a Frequency Counter to the Output Jack. 

(3)  Load a 3 kHz Speed Wow/Flutter Tape (DA09006A) 

and play it back. 

(4)  Referring to Fig. 5.3, adjust the Tape Speed 

Adjustment Volume (VR501) incorporated in the 

Capstan Motor to obtain 3,000 Hz on the Frequency 

Counter. 

CCW:  Motor drives slowly. 

CW:  Motor drives fast

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