Nakamichi 481 Service Manual - page 15

14 

2.3.5.  Record Control Circuit 

Refer to Fig. 2.3.8 circuit diagram. 

RECORD mode is set by pressing Record Button, then 

Play Button together. By pressing Record Button, the  

Krec. signal becomes L, Q419 is turned ON, Q421 is turn 

ed ON, and the record lamp is illuminating. Then, by pres 

sing Play Button further, the Kplay signal becomes 

L,Q418 is turned ON, the PLAY signal becomes H (+24 

VS), and Q420 is turned ON. 

Accordingly, the base current flows to Q403 via C406 

connected to the base of Q403, and Q403 is turned ON 

pulse-likely. 

The output of Q403 is fed to the control motor drive circuit 

and acts to bring the cam to the record position, When 

Q403 returns to OFF, the cam then moves to the 

play position and stays there, thus the mechanism is set 

to RECORD mode. 

Record circuit is designed to protect from the erroneous 

setting of RECORD mode even if wrong record button 

operation is made. 

Q422 is turned ON during FF or REW mode, or when the 

cam is set to the play or pause position, i.e., PLAY or 

PLAY/PAUSE mode. In this case, as D422 is grounded by 

Q422, Q421 is not turned ON and the record lamp is not lit 

even if Record Button is further pressed. 

Further, the base of Q420 is grounded via D419 and 

Q422, consequently, Q420 and Q403 are not turned ON 

and no pulse is output from 

Q403 to the control motor 

drive circuit. 

R/P Switch : When R/P Switch on the Main P.C.B. 

is in the record position, +24 V is 

applied, but when it is in the play 

position, no voltage is applied. 

The modes in which the amplifier circuit is not muted are 

2.3.6. Mute Signal 

Refer to Fig. 2.3.9 circuit diagram. 

When 

Q416 is turned ON, the Mute 

= 

H signal is fed to 

the amp. circuit and the amp. circuit is muted. 

The condition that the amplifier circuit is muted are 

(Mute = 

H):