Troubleshooting LQ-300 Service Manual
Table 5-8. Repairing the Printer Mechanism (Continued)
Problem
Symptom
Cause
Checkpoint
Soiution
Self-test A particular
The
printhead
Measure the pnnthead
ooil
Replaoe
the
printing is
dot is missing. is defective.
resistance. it should be
printhead
(and
abnormal.
approximately 54.7
Q.
if the
drivers, if
printhead
is shorted, also
necessary).
check the drivers.
Check to see if the dot wires
Replace the
are worn.
printhead.
The printing is The
printhead
Check whether the tips of the
Replace the
too light, or the
is defeotive. wires are worn.
printhead.
print
density is
The
platen
Set the gap adjustment lever to
Adjust the
not uniform.
gap is not the first position, and check the
gap. Refer to
properly
platen gap. The appropriate
Section 4.1.1,
adjusted.
value is 0.45 mm.
Platen Gap
A@Mnent.
Paper feed is
Printing is per- Foreign
Perform a visual check of the
Remove any
abnormal.
formed but the
substances
paper path.
foreign
paper is not are
iodged
in
substances.
fed or is not
the paper path.
fed uniformly.
The PF motor
Check that no foreign Remove any
is not driving
substance is
iodged
between
foreign
the gear the gears and that the gears
substances.
correctly. are not broken or worn.
Replaoe
the
PF motor
reduction
gears.
Replace the
paper pickup
gears.
The PF motor Measure the coil resistance for
Replace the
is defective.
the PF motor. The approximate
PF motor (and
value should be 56
Q.
if the
drivers, if
motor is shotied, also check
necessary).
the drivers.
The
ribbon
The ribbon is
The ribbon
Remove the ribbon cartridge,
Replace the
‘eed is
not turning.
cartridge is rotate its ribbon feed knob
ribbon
~bnormal.
defective.
manually, and see if the ribbon
cartridge.
feeds normally.
Foreign Cheek whether the RD ratchet Remove any
substances
rotates when the carriage is
foreign
are caught in
moved
manuaily. substances.
the gears. .
Replace the
ribbon feed
mechanism.
The ribbon
The planetary Move the carriage manually;
Replace the
feeds properly gear is
check whether the planetary
ribbon feed
only when the defective.
gear turns in reverse and
mechanism.
carriage
engages the gear.
moves in one
direction (i.e.,
it fails to feed
when the
carriage
moves in the
other
direction).
.,.
5-14
Rev.A
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