1-12
Troubleshooting
Rev.D
Confidential
Test Points on the Main Circuit Board Unit
After a main circuit board unit failure, one basic method for diagnosing the cause of the problem
on the main circuit board unit is to check the power supply line. Use the following table to check
the power supply line. First, check step number 1, and proceed to the next step if that is not the
problem.
Table1-4 Checking the power supply line
Step
#
Type of Voltage
Location of
Measurement
Condition of
Measurement
Normal
Value
Presumed Cause of the Error
1
Voltage input
from the power
supply
CN29, pin 1
Output when
the power
supply is ON.
24 V
±
10
%
It is possible that the problem is pre-
arcing of the F1 fuse. The fuse may
have pre-arced because of an
unusual input circuit.
Always replace the fuse after
removing the cause of the pre-arcing.
If you do not remove the cause of the
pre-arcing, and replace this fuse, the
problem may expand to
misoperation. Also, always use the
specified type of fuse when replacing.
2
Voltage input
from the power
supply
U11, pin 1
Output when
the power
supply is ON.
24 V
±
10
%
It is possible that the problem is pre-
arcing of the R3 fuse. The fuse may
have pre-arced because of a
problem in the logic power supply
circuit or because of a VCC over-
voltage.
If pre-arcing of the R3 fuse happens,
do not repair the main circuit board
unit. The quality of several parts on the
circuit board is weakened by pre-
arcing of the R3 fuse and safe
operation cannot be guaranteed.
3
Logic voltage
(VCC)
VCC pad
(near L2)
Output when
the power
supply is ON.
5 V
±
5
%
It is possible that the logic power
supply circuit has malfunctioned.
If you find this line has a problem, do
not repair the main circuit board unit.
The quality of several parts on the
circuit board is weakened, and safe
operation cannot be guaranteed.
4
Logic voltage
(VCC-PWR)
VCC-PWR pad
(near U14,
pin 40)
Output when
Q51 (C) is "0."
(24V SW1="H")
5 V
±
5
%
The logic power supply circuit or Q44
could have malfunctioned.
5
Logic voltage
(VCC-PWR2)
U19, pin 8
potential
Output when
Q60 (C) is "0."
(24V SW2="H")
5 V
±
5
%
The logic power supply circuit or Q59
could have malfunctioned.
6
Logic voltage
(VCC_SEN)
CN30, pin 5
potential
Output only
when there is
output sensor
conductivity
when CPU
output port
(SEN_PWR) is "L."
5 V
±
5
%
The logic power supply circuit or Q44
could have malfunctioned.
Summary of Contents for U675 - TM Color Dot-matrix Printer
Page 2: ......
Page 4: ...Confidential ii Revision Table ...
Page 34: ...1 22 Troubleshooting Rev D Confidential ...
Page 168: ...2 134 Assembly and Disassembly Rev D Confidential ...
Page 180: ...Appendix A 2 Service Tools and Lubricants Rev D Confidential ...
Page 270: ...Appendix D 82 Product Overview Rev D Confidential ...
Page 322: ...Appendix J 2 Screw Types Rev D Confidential ...
Page 324: ...Appendix K 2 Parts Layout Rev D Confidential Main Circuit Board Unit Solder Side memory board ...
Page 325: ...SEIKO EPSON CORPORATION Printed in Japan EPSON ...