Epson Stylus Color 980 Service Manual page 65

EPSON Stylus Color 980
AN7 (Pin 112)
The TH1, located between 2 pre-driver ICs (the head driver ICs;
IC15 and IC16) on the main board, monitors temperatures around
the board. A Pre-Driver IC is exclusively developed to create
intricate trapezoidal waveforms which vary depending on the model.
It uses +42 VDC and high frequency to produce trapezoidal
waveforms. Therefore, if any relevant trouble has occurred, it is
assumed that the driver is overheated. The TH1 works to detect this
kind of unexpected rise in temperature at an early stage and stop
printing.
AN6 (Pin 111)
Four power transistors (Q3 - Q6) used for trapezoidal waveform
production are directly attached with screws to the large heat sink (a
radiation plate) on the main board. Since the printhead supported by
the Stylus Color 980 supports very high driving frequency (28.8
KHz), higher than ever, and a large amount of PZT, radiation from
the discharging transistor used for trapezoidal waveform production
is huge. Therefore, the cooling fan on the board forces out heat
around the radiation plate. A thermistor fixed on the radiation plate
sends signals to the AN6 port of the CPU to allow the CPU to
manage the cooling fan's on/off operation.
AN5 (Pin 110)
The electrical signal input to this port is a temperature signal sent
from the thermistor included in the printhead unit. The function of
this thermistor is, same as before, to precisely detect temperatures
around the printhead and feed back information to the C380 main
board. Based on the fed back information, the printer manages
subtle change in the voltage level of the head drive trapezoidal
waveform, and also can eject the correct amount of ink as it is
aimed at any temperature.
Operating Principles
AN4-ANO (Pins 1, 2, 9, 10, 4)
The nozzle selector IC is attached inside the printhead. It
determines which nozzle is used to fire ink according to serial data
sent from the ASIC (IC2). A temperature detection circuit included in
the nozzle selector detects the temperature of each actuator in the
5-row PZT array. This must be performed to avoid false firing. If the
printhead continues the firing motion, but no ink is ejected, the
temperature inside the printhead rises to 100 C and the printhead
might be damaged as a result. To prevent this from happening, the
abnormal temperature detection circuit is included in the nozzle
selector circuit.
The followings are possible reasons for false firing:
1. If an ink cartridge has been removed before its life end and is
2. Serious dot missing can also cause false firing. In this case,
3. Strong vertical impact applied to the head causes a
Electrical Circuit Operation Principles
installed again, the ink consumption counter value is upset, and
the counter fails to detect the actual remaining ink level. This
wrong operation dangerously causes the printhead to keep
firing without any ink remaining in the cartridge.
there is enough ink in the cartridge, but it does not properly flow
into the head because of a clogged nozzle(s). If the PZT is
driven without any ink flow, heat generated by the nozzle
movement can not be released, and this makes the
temperature around the head abnormally high.
considerable amount of ink around the nozzle to leak all at
once as well as damages meniscus on the head surface. As a
result, ink does not properly eject at the next printing and ends
up in a false firing status.
Revision A
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