Epson TM-U950 - Page 126

Rev. A Troubleshooting 4-13
TM-U950/U950P Technical Manual
.
Table 4-1. Initialization Problems
Problem Probable Cause Level Checkpoint Action
Printer does not operate
at all.
Output voltage of
external power supply
unit or internal regulator
circuit is not normal.
BCheck 24 V input
voltage at CN4 and
output voltage of
switching regulator.
Replace regulator IC
(U9). Replace external
power supply unit.
Reset circuit failure B Check voltage level at
RESET pin (pin 28) of CPU
(U12), U5 (reset: LOW).
Replace IC (U4.)
CPU oscillator circuit
failure
B Check oscillator output. Replace oscillator (X1).
Program ROM selection
failure
B Check input at pin 22 of
IC (U15).
Replace CPU (U12),
gate array (U19), and IC
(U11, 13, and 18).
RAM selection failure B Check input at pin 20 of
IC ((U16).
Replace CPU (U12),
gate array (U19), and IC
(U11, 13, and 18).
Gate array selection
failure
B Check input at pin 59 of
IC (U19).
Replace CPU (U12) and
IC (U11, 13, and 18).
Carriage-head vibrates,
emits an unusual sound,
and becomes error at
power-on.
Excessive tension of
carriage transmission
belt
A Check tension of
carriage transmission
belt. Nominal value: 190
(
±
)10g(.42 (±).022 lbs)
Adjust the tension as
described in the
adjustment section of
Chapter 5.
Detector-H.P. sub
assembly failure
B Use an oscilloscope to
check the detector
output signal when the
carriage-head passes
the detector.
Replace the detector-
H.P. sub assembly.
Carriage-head vibrates,
emits an unusual sound,
and becomes error at
power-on.
Wire break or bad
solder point between
connector and carriage
motor terminals.
B Check continuity
between respective
terminals.
Replace wiring board
assembly.
B Check solder condition. Resolder as required.
Motor-carriage
defective
B None of the above
checks solves the
problem.
Replace motor-carriage.
Carriage-head first
moves normally, but
then hits the left border
of the frame-carriage
making an unusual
sound.
Too little backlash
between carriage
motor gear and
carriage feed pulley.
A Check backlash.
Nominal value:
0.1(±)0.05mm (.0039
(±).0020”)
Adjust the backlash as
described in the
adjustment section of
Chapter 5.
Gear wear, damage, or
contamination
A Check gears for wear
and damage.
Replace any damaged
gear.
A Check for dirt deposits or
other foreign matter.
Remove any dirt
deposits or foreign
matter.
CONFIDENTIAL