Epson DFX-5000+, Service Manual

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Operating Principles
Printhead Driver Circuit
Figure 2-31 shows a printhead driver circuit block diagram. Print data lines from
IC7 are active when LOW, but the
(IC6 and IC7) convert these
signals to HIGH. When ports to of IC7 go LOW, the FET gates are
biased, and the are turned on so that current flows through the printhead
coil. When the HD port ofIC7 goes HIGH, the are turned the
printhead coil current is cut. The trigger power is VDC. If extra
current charges into the head coil (more than 62 VDC), the extra current escapes
to the VDC line using Zener diodes D4 to D6. (This prevents a large current
from suddenly flowing into the head driving coil.) Two VDC lines (VH and VP)
assign the common voltage for the printhead coil. Pins HD3, HD5, HD7,
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 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 head driver status. head driver IC shorts, CPU
port P34 detects a LOW level and the CPU sends the DRERR (Driver Error)
signal to the Cl 17 power supply board assembly. When the Cl 17 power supply
board assembly receives this signal, it stops the output voltage and the printer
beeps.
EPSON Service Manual
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