Specifications
REV.-A
Figure
2-47
shows
the timing
for discharge/charge pulse.
Figure 247. Timing for Discharge/Charge
(2)
Printhead
Voltage Supply Circuit
Pulse
The viscosity of ink is subject to change due to the temperature. If the viscosity is too high, ink injection
becomes difficult. To eliminate this difficulty, the head drive voltage (Vh: the +35
VDC voltage boosted
to 83 -123.7
VDC
in this circuit) is controlled based on the ink temperature detected by the thermistor.
That is, the temperature is fed back to the voltage supply circuit and controlled by
TL494.
Since each
printhead
produced shows slightly different characteristics, this difference must be
neutralized by adjusting the head drive voltage. For this purpose, several
zener
diodes (used for
detecting output voltage) and a
DIC
jumper are provided. When the
printhead
or the MAIN board is
replaced, adjust the
DIC
jumper to connect the
zener
diodes in proper arrangement.
For safety, this circuit is
automatically
disconnected when a case open condition is detected.
2.3.7 Pump Motor Drive Circuit
Figure 2-48 shows the block diagram of the pump motor drive circuit.
A DC motor is used to drive the pump. The drive circuit is controlled by the collector-follower
bridge -
SOH03
(IC
16).
The rotational direction of the motor is controlled through the ports on
E05A65. If PMCW signal is
transmitted from
PCO,
the motor rotates
CW.
If
PMCCW
signal is transmitted from PC 1, the motor rotates
Ccw.
CPU
GA
Pump
uPD70325
(IC5)
E05A65
(IC12)
SOH03
(IC16)
t
MOTOR
I
/
Bus
PM+
I
Pcl
NPN2B
[
PM-
1
Pco
PNPIB
1
I
I
1
I
I
1
I
I
I
c’
.,
\
<
.!
,
/’
c)
...
...”5
.’.
-
Figure 248. Block Diagram of Pump Motor Drive Circuit
2-36