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.
B
Check 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
Summary of Contents for TM-U950P - B/W Dot-matrix Printer
Page 2: ...Technical manual TM U950 TM U950P English 4005789 Copied Date 199 Copied by ...
Page 3: ...EPSON SEIKO EPSON CORPORATION Printed in Japan E96010130 0000SE CONFIDENTIAL ...
Page 8: ...iv Rev A Revision Sheet Revision Page Altered Item and Contents Rev A CONFIDENTIAL ...
Page 13: ...1 2 Features and General Specifications Rev A Figure 1 1 TM U950 Appearance CONFIDENTIAL ...
Page 119: ...4 6 Troubleshooting Rev A CONFIDENTIAL ...
Page 121: ...4 8 Troubleshooting Rev A CONFIDENTIAL ...
Page 124: ...Rev A Troubleshooting 4 11 TM U950 U950P Technical Manual End End CONFIDENTIAL ...
Page 138: ...Rev A Troubleshooting 4 25 TM U950 U950P Technical Manual Action 1 Action 3 CONFIDENTIAL ...
Page 226: ...6 2 Appendix Rev A Circuit 1 CONFIDENTIAL ...
Page 227: ...Rev A Appendix 6 3 TM U950 U950P Technical Manual Circuit 2 CONFIDENTIAL ...
Page 228: ...6 4 Appendix Rev A Circuit 3 CONFIDENTIAL ...
Page 229: ...Rev A Appendix 6 5 TM U950 U950P Technical Manual Circuit 4 CONFIDENTIAL ...
Page 230: ...6 6 Appendix Rev A Circuit 4 Circuit 5 CONFIDENTIAL ...
Page 231: ...Rev A Appendix 6 7 TM U950 U950P Technical Manual Circuit 6 Circuit 7 CONFIDENTIAL ...
Page 232: ...6 8 Appendix Rev A Circuit 8 CONFIDENTIAL ...
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