User manual NAKAMICHI 481 SERVICE MANUAL

[. . . ] General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Headblock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] This negative pulse acts to turn ON Q424 and Q426, as a result, C411 is charged up to +24 V. FF or REW mode is set after passing through a certain period of STOP mode in the same manner as above (1). (c) Power-mute = L The Power-mute = L pulse is generated when Power Switch is turned ON or OFF. During the Power-mute sig -nal is L, the voltage at the point A becomes lower than the emitter voltage of Q424. Subsequently, Q424 and Q426 are turned ON, C41 1 is charged up to +24 V, and shut-off is activated in the same manner as above (b). (d) Memory Rewind During REW mode and with Memory Rewind Switch turned ON, C414 is grounded when the tape counter comes to "999" and Q431 is turned ON pulse-likely. As a result, Q430 is turned ON, and shut-off is activated resulting in STOP mode. 13 2. 3. 5. RECORD mode is set by pressing Record Button, then Play Button together. 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. 2. 3. 6. When Q416 is turned ON, the Mute = H signal is fed to the amp. The condition that the amplifier circuit is muted are (Mute = H): 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 14 2. 3. 7. Control Motor Drive Circuit Refer to Fig. The control motor is turned by varying amounts, according to which control button is set. [. . . ] Further, excessively weak take-up torque or strong take-up torque may cause defective tape travelling. The N-481 is intended to be an adjustment-free Model, however if the similar matters as above should be noted, please replace the Reel Hub Ass'y to obtain appropriate take-up torque. Record Switch Linkage Adjustment (1) Set the N-481 in stop mode. (2) Loosen the screw of the Record Spring Holder, and shift the Record Spring Holder in order to remove the looseness of the Linkage Wire as shown in Fig. [. . . ]