Adjustments - Epson LQ-870 Service Manual

Problem
A particular dot fails
to print.
The printing is too
light, or the print
density is not uniform. L
Paper feeding is Printing is performed,
but the paper is not
abnormal.
fed, or is not fed
uniformly.
Table 5-6. Repair of the Printer Mechanism (Cont.)
Cause
The printhead is
defective.
The printhead is
defective.
The platen gap is not
properly adjusted.
A foreign substance
is lodged in the paper
path.
The paper-feed motor
is not driving the gear
correctly.
The paper-feed motor
is defective.
Measure the coil
resistance of the
printhead. The normal
value is approximately
16.7 ohms.
Check whether the dot
wire is worn.
Check whether the tip
of the dot wire is worn.
Set the gap adjust lever
to the second position,
and check the gap
between the tip of the
printhead and the
platen.
The appropriate value is
0.38 mm.
Perform a visual check
of the paper path.
Check that no foreign
substance is lodged
between the gears, and
that the gears are not
broken or worn.
Measure the coil
resistance for the
paper-feed motor.
The approximate value
should be 56 ohms (for
the Shinano Kenshi
motor) or 51 ohms (for
the Seiko Epson motor).
5-20
Solution
Replace the
printhead.
Replace the
printhead.
Replace the
printhead.
Adjust the gap.
Refer to Section
4.1.2, Platen Gap
Adjustment.
Remove any foreign
substance.
Remove any
l
foreign substance.
Replace the
l
paper-feed
reduction gear.
Replace the platen
l
gear.
Replace the paper-
feed motor.