Service manual
DEX-5000+
Servb
Manual
Dperating
Ptinciphs
2.3.8 Plunger Driver Circuit
Figure 2-30 shows a block diagram of the plunger driver arcuit, and Table 2-9 provides the plunger
switching pattern. The plunger is driven using three switching patterns. Gate array general
purpose ports
PLP
and
PLN
output the plunger coil drive signals. The CPU latches the switching
data in the gate array. When the
PNP
port of the gate array turns off switching transistor
Q19,
transistor
Q17
is turned on and the supply voltage (VP) flows into the plunger coil. When
switching transistor
Q19
is turned on, transistor
Q17
is turned off and the hold voltage (+5 V) flows
into the plunger coil using general purpose port
PLN
of the gate array.
VP
T
EOSA87
(IC7)
PNP
NPN
-
E
Q19
PLP
Q17
~
●
*
B
-c B
-U
-0
1-
Z
+5
0
A
c)
0
=
)
(
B
-
E
I
●
Q27
~
GP
Figure 2-30.
Piunger
Driver Circuit
Tabie
2-10.
Piunger
Switching Pattern
Suspension Roller
Ststus Q17
Q27
closed
off off
Closed
+
open
On
off
Closed with hold
vottage
off
On
@>
2.3.9
Printhead
Driver Circuit
c~’
Figure 2-31 shows a
printhead
driver arcuit block diagram.
lhe
print data lines from
IC7
are active
when they are LOW, but the invertor ICS
(IC6
and
IC7)
convert these signals to HIGH. When ports
HD1 to HD8 of
IC7
go LOW, the FET gates are biased, and the FETs are turned on so that current
flows through the
printhead
coil. When the HD port of
IC7
goes HIGH, the FETs are turned off and
the
printhead
coil current is cut. The trigger power of these FETs is +12 VDC. If extra
curnmt
charges into the head
mil
(more than 62
VDC),
the extra current escapes to the +35 VDC line using
Zener diodes D4 to D6. (This prevents a large current from suddenly flowing into the head driving
coil.) Two +35 VDC lines
(VH
and VP) assign the common voltage for the
pnnthead
coil.
Pins
HDl,
HD3, HD5, HD7, HD8, and HD9 are supplied by the VH
(HDCOM2)
line (CN6 pins 5,6,7,8, and
10). Pins HD2, HD4, and HD6 are supplied by the VP
(HDCOM1)
line (CN6 pins 11,12, and 14).
The CPU monitors the head temperature and head fan temperature. When the temperature rises
abnormally, printing stops at once until the temperature cools. The CPU also monitors the
@d
driver status. If the head driver
IC
shorts, CPU port
P34
detects a LOW level and the CPU sends
the
DRERR
(Driver
Emor)
signal to the
C117
power supply board assembly. When the C117 power
supply board assembly receives this signal, it stops the output voltage and the printer beeps.
c)
. .
;:..
,:.-..
!.
,..
Rev.
A
2-33
.