Epson U375 - TM B/W Dot-matrix Printer, Technical Manual

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4-10
Table 4-2. Printing Quality Problems (continued)
Level
B
B
B
A
B
B
B
A
A
B
Problem
Dots are dropped ir-
regularly.
Character width
changes irregularly.
Print is very faint.
Checkpoint
Check the FFC for continuity.
Check dot wire tip for paper or
ink deposits.
Above two checks have been
passed.
Check Spring-Belt tension for
deformation.
Check gears and pulleys for
dirt deposits or other foreign
matter.
Check gears and pulleys for
wear and damage.
Above three checks have been
passed.
Check ribbon for faint ink and to
see if the ribbon feeds smoothly.
Check platen gap. Nominal
value: 0.65
±
0.05 mm (.026
±
.0020")
Check to see if the head cur-
rent width setting command,
GS E is set to "standard" (
n=1).
Table 4-3. Printer Mechanism Problems
Checkpoint
Check Microswitch sub-as-
sembly continuity.
Check to see if the spring is
unhooked.
Check to see if the spring is
unhooked.
Check resistance of the sole-
noid. (Nominal value: approx.
10
Ω ±
10%)
Check attaching position of the
solenoid.
Check signal of connector
CN12.
Action
R e p l a c e M i c r o s w i t c h
sub-assembly.
Hook Spring-J holding
roller.
Hook Spring-Form stop-
per.
Replace Solenoid-Paper
holding switching.
Adjust the solenoid attach-
ing position as described
in
Main Assembly 7 in Sec-
tion 5.3.3.
R e p l a c e M a i n c i r c u i t
board unit.
Problem
Paper roll is not loaded
when paper load switch
is pressed.
It is hard to insert cut
sheet, or it cannot be
inserted.
Level
B
A
A
B
A
B
Probable Cause
F F C - P r i n t h e a d w i r e
break
Print head operation fail-
ure
Print head unit wear
Belt tension is loose.
Carriage drive area con-
tamination
Carriage drive parts wear
or damage
Print head unit wear
Ribbon cassette life end
or failure
Platen gap is not adjusted
correctly.
Head current width is not
set correctly. ("Standard"
is selected when printing
on 2-ply, slip, or valida-
tion paper.)
Action
Replace FFC-Print head.
Clean wire tip.
Replace Print head unit.
Adjust the belt tension as
described at step 18 in
Sub-assembly I in Section
5.3.2, or replace Spring-
Belt tension.
Remove any dirt deposits
or foreign matter.
Replace any damaged
parts.
Replace Print head unit.
Replace ribbon cassette.
Adjust the gap as de-
scribed in
Adjustment D in
Section 5.3.4.
Correct application soft-
ware setting.
Probable Cause
Microswitch failure or wire
break
Spring-J holding roller
is unhooked.
Spring-Form stopper is
unhooked.
Solenoid-Paper holding
switching wire break
Poor adjustment of
Solenoid-Paper
holding switching
position
Solenoid drive signal fail-
ure
CONFIDENTIAL