Epson 2080 - LQ B/W Dot-matrix Printer, Руководство по обслуживанию

Страница: 26 / 55

LQ-2080 Revision A
Operating Principles Control Circuit 26
2.3.2 Printhead Driver Circuit
The standard voltage for the A/D converter is made in ZD1 and input to
CPU port 78. Based on this standard voltage, the A/D converter in the
CPU operates. Port 74 monitors the +35 V line between R139 and R140
to determine the printhead driver pulse width. Using the monitored
voltage, the CPU converts the voltage to a digital value and decides the
printhead driver pulse width, and then transports the data to the gate
array via CPU port 15. Based on the monitored voltage, the CPU
decides the printing interval. Port 73 monitors the printhead temperature
to protect the printhead. If the temperature exceeds 95
°
C (213
°
F),
printing is stopped.
Figure 2-5. Printhead Drive Circuit
G a t e
A r r a y
C 1 9
Z D 1
+ 3 5 V
7 8 7 9
7 4
7 3
R 1 4 0
R 1 3 9
+ 3 5 V
R 1 5 8
A d d r e s s
D a t a L i n e
P r i n t h e a d D r i v e S i g n a l
H D 1 - H D 2 4
P r i n t h e a d D r i v e T r a n s i s t o r Q 1 - Q 2 4
C N 8 a n d C N 9 ( P r i n t h e a d )
H T M P
+
C 6 8
+ 3 5 V + 3 5 V
1 1 1 1 5
C P U