Epson 2080 Service Manual - Page 26

Printhead Driver Circuit - lq printhead

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LQ-2080 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. Revision A Operating Principles Figure 2-5. Printhead Drive Circuit Control Circuit 26

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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 te
A
rray
C
19
ZD
1
+35V
78
79
74
73
R
140
R
139
+35V
R
158
A
ddress
D
a ta L in e
P
r in th e a d
D
r iv e
S
ig n a l
H
D
1 - H
D
24
P
r in th e a d D
r iv e T r a n s is to r
Q
1 - Q
24
C
N
8 a n d C
N
9 (P
r in th e a d )
H
TM
P
+
C
68
+ 3 5 V+ 3 5 V
111
15
C
P
U