– 19 –
Notes: Adjust motor speed with VR
adjustment and T1 signal to
1660 Hz ± 30 Hz.
Fig. 3-15 Motor drive circuit (example)
R1 10 KΩTR1 2SA950
R2 3.3 KΩTR2 2SC1740
R3 6.8 KΩ1/6 W TR3 2SA1175
R4 2.2 KΩTR4 2SD882
R5 1.2 KΩTR5 2SB1359
R6 10 KΩTR6 2SD1637
R7 20 KΩIC1 SN74LS05
C1 0.47 µF (Film) IC2 M51971L (MITSUBISHI)
C2 0.033 µF (Film) VR 6.8 KΩ
C3 0.022 µF (Film)
3.8.1 FG Circuit
The motor control circuit with a Frequency Governor circuit maintains the printing speed at the settings. It is
mainly constructed of a Speed Control IC (IC2) and a Power Transistor TR6 shown in Fig. 3-15. It measures
the number of rotations of the Carriage Motor from the Timing Signal 1. This signal is then compared to the
standard signal to control the speed by controlling the voltage energizing the Carriage Motor.
3.8.2 Merits of the FG Circuit
The FG circuit maintains a stable output regardless of the environment where it is being used.
It maintains stability even at high speeds.
It protects the head because the speed is stable.