45
Table 12.2 Fault Analyses (Continued)
No. Fault Cause Remedy
5 Arc does not start. High voltage is not
obtained.
Refer to No. 4.
−
Gas flow stops by
turning OFF the
power supply
switch.
Gas circuit failure Check the printed board (MB2).
6 Gas does not
stop.
Gas flow does not
stop even by
turning OFF the
power supply
switch.
Foreign matters in magnetic valve
MV
Check the magnetic valve MV. Replace
it if necessary.
7 Current adjustment does not work.
Current reference signal failure
Current adjusting VR failure
Printed board improper contact or
disconnection
Check the current reference signal.
Check the current adjusting VR.
Check the set voltage.
Check the printed board (MX).
Diode (REC1) breakage Check the diode. Replace it if necessary.
8 Power supply switch trips and cannot be
turned ON.
Secondary side transistor (UP, UN,
VP, VN) breakage
Check the transistors (UP, UN, VP, and
VN). Replace them if necessary.
Rated operatonal ratio exceeded Use within the rated operational ratio.
Input voltage excessive Use at rated input voltage.
9 Fault indicator lamp flashes.
Short of cooling water pressure Check the piping system.
10 Fault indicator lamp lights.
Excessive current flows in the
primary circuit.
Check the transistors (UP, UN, VP, VN),
the drive mold (DM15C), and the diodes
(S21 to S24). Replace them if necessary.
Pulse selector switch is set to NO or
switch failure
Check the switch. Replace it if
necessary.
11 Pulse welding is
disabled.
Other operations
can be performed.
Printed board failure Check the printed board (MB2).
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