Plunger Driver Circuit; Printhead Driver Circuit - Epson C117001-N - DFX 5000+ B/W Dot-matrix Printer Service Manual

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
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.

2.3.9 Printhead Driver Circuit

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.
. . ; : . . , : . - . .
Rev. A
is turned on and the supply voltage (VP) flows into the plunger coil. When
Z
B
I
Figure 2-30. Piunger Driver Circuit
Suspension Roller Ststus
closed
Closed + open
Closed with hold vottage
NPN
-
E
*
B
+5
A
-
E
off
On
off
.
VP
T
0 =
GP
off
off
On
2-33