Epson PX-8 Technical Manual page 156

REV.-A
------------------------------------~O
HSVV1
VBSVV
HSVV2
E+ ORANGE
,-------+---0
E- BLU E
Q2
2SD1290R
.---~_.----+_------r___oHPMl
RED
HPM2 BLACK
QS
2SObOlR
R9
1.51:
GP
2.71
R.3 CIO
.1
ERAH
HMT
R.2
lCS
101
I 6 4069
------------~~--------------+_~----__oM+
RED
---------------------------------------0
M- BLACK
Fig.3-12 Head Pinch Motor Control Circuit
When the HMT signal goes high, the transistors 05 and 02 are turned on and the VBSW voltage
is supplied to HPM1 (the positive side terminal of the motor), revolving the motor which in turn
causes the P-Iever assembly to move back and forth.
When the HMT signal is turned low to stop the motor, the output of IC5 turns off and the output
of pin 6 goes high, turns off transistors 05, 02, and turns on 03. This causes the HPM1
line to be shorted to ground, and applies a brake to the motor, preventing revolution by inertia. If
the motor continued revolving by inertia, the read/write head position and the pinch roller's con-
tacting pressure against the capstan shaft would deviate from the specifications, and such failures
as read/write error would occur.
The zener diode ZD1, connected at the base of 05 maintains the voltage supplied to the motor
below the VBSW voltage (approximately 5V). - (A higher motor drive voltage would increase the
motor inertia as described above.)
3.1.6.3. Erase Circuit
When the ERAH signal is activated low, transistor 03 is turned on. This causes a current from the
VBSW line to ground passing through the erase winding of the read/write head, and erasing
previously written tape data. This circuit operates only during write.
Read/Write Head Structure
Both the read/write and erase heads make use of leakage flux.
\ \ ) _ Leakage flux
Data are actually written on the tape at the
copre slit where leakage flux is generate.
Fig.3-13 Read/Write Head Structure
3-10
/