Nakamichi 481 Service Manual - page 11

11 

2.3.  Mechanism Control Circuits 

2.3.1. Outline 

(1) Control Button Operation 

Record, Rewind, Stop, Play, and Fast-Forward Buttons 

consist of a 5—way switch and are interlocked each other. 

When one button is pressed, it is mechanically locked in 

the ON state and other buttons are mechanically released. 

Stop Button is of momentary type and acts to release 

other buttons mechanically. But it is not used to control 

circuits electrically. Pause Button is independent from 

others and is of push-on and push-off type. Note that if 

two or more buttons are pressed simultaneously, these 

buttons are locked in the ON state. Under the normal con 

trol button operation, only Record and Play Buttons are 

pressed simultaneously to set the N-481 in RECORD 

mode. In this case, both Record and Play Buttons are 

locked in the ON state and RECORD mode is set. The 

N-481 is designed so as not to occur erroneous operation 

even if two or more buttons are pressed simultaneously. 

Further, to prevent from abnormal tape tension, loosening 

of tape, etc., the N-481 changes its mode by passing 

through momentary STOP mode automatically, for ex 

ample, when PLAYBACK mode is commanded while FF 

mode, or REW mode is commanded while FF mode. 

(2) Auto Shut-off Function 

Refer to Fig. 2.3.1 basic circuit diagram. 

During FF, REW, or PLAY (PLAYBACK or RECORD) 

mode, auto shut-off will be activated when the tape comes 

to end, and FF, REW, or PLAY mode is changed to STOP 

mode. 

Following explanation is made in regard to REW mode: 

In the initial condition, Q428 is turned ON and +24 VS is 

applied to the emitter of 

Q402. When Rewind Button is 

pressed, it is locked in the ON state, as a result, 

Q402 is 

turned ON, the REW signal becomes H, and the N-481 is 

set in REW mode. 

When tape-end comes, auto shut-off is activated and 

Q428 is turned OFF, as a result, +24 VS is shut-off, Q402 

is cut off, and the REW signal becomes L. In this way, 

REW mode is changed to STOP mode. (Note that Rewind 

Button is still locked in the ON state.) When Play Button is 

pressed in this state, REW Button is released and 

Q428 is 

turned ON, as a result, +24 VS is applied again, 

Q418 is 

turned ON, the PLAY signal becomes H, and the N-481 is 

set in PLAY mode. 

(3)  Unattended Recording or Playback 

Unattended recording or playback is carried out by the 

use of the lock mechanism of control button, therefore, no 

special circuit is required for this purpose. 

If Record and Play Buttons are pressed, unattended re 

cording can be carried out when the power is connected 

to the N-481. If only Play Button is pressed, playback will 

be carried out when the power is connected to the N-481.