Epson PX-8 Technical Manual page 150

REV.-A
3.1.5 MMC Board
The MMC board consists of two major sections, the motor drive control and read/write, which
provide the following functions:
3.1.5.1 Motor Control Section
The motor control section occupies the upper half of the MMC board and controls the capstan
motor and head pinch motor drive, and tape count detection. The individual circuits are discussed
in the following:
(1) Capstan motor drive circuit
This circuit uses two ICs: IC1 and IC2. IC1 controls motor drive circuit switching and IC2
controls motor revolution speed .
• Motor drive circuit
Fig. 3-5 shows the internal circuit of IC1.
VB SW
MTA
MTB
QI
B
r-----<>
Ie 2
Pin 6
D2
Q4 Q6
M+ M-
I /-..... I
L_J
M'r'1-.J __ _
\ 1_
Capstan motor
'-
....
Fig. 3-5 Motor Drive IC Circuit
The circuit switches the polarity of the voltage applied to the capstan motor. Simplified circuit
descriptions follow. While the actual circuit operation is more complicated, the basic operation is
the same.
3-4