Manual 0-2957 4-11 TROUBLESHOOTING
4.08 Pilot Arc Problems
WARNING
The following tests must be performed with the power
supply connected to primary input power. There
are extremely dangerous voltage and power levels
present inside this unit. Do not attempt to diagnose
or repair without proper training in power elec-
tronics measurement and troubleshooting tech-
niques.
Locate your symptom below:
A. Torch will not pilot; gas flows; AC indicator
ON, GAS , TEMP , and DC indicators
OFF
A
Art # A-03988
1. Gas pressure is below power supply minimum require-
ment
a. Adjust gas pressure per pressure setting label
on power supply.
2. Upper O-ring on torch head is in wrong position.
a. Remove shield cup from torch; check position of
upper O-ring. Correct if necessary.
Upper Groove
with Vent Holes
Must Remain Open
Threads
Upper O-Ring
in Correct Groove
Lower O-Ring
Art # A-03725
3. Faulty IGBT(s)
a. Measure between the following points on the
IGBTs:
• IGBT A: E4 to E10
E10 to E20
• IGBT B: E23 to E27
E27 to E30
Voltage should be approximately 20 vdc before
the start signal is active. If voltage measures
greater than 100 vdc when the start signal is
active, replace the respective IGBT(s).
B. Torch will not pilot; RUN / RAPID AUTO RE-
START /SET switch in RUN or RAPID AUTO
RESTART; AC
and GAS indicators ON;
Temp and DC indicators OFF
A
Art # A-03990
1. Gas pressure is below torch minimum requirement
(NOTE: Minimum pressure for power supply opera-
tion is lower than minimum required for torch opera-
tion.)
a. Adjust gas pressure per pressure setting label
on power supply.
2. Torch tip, starter cartridge, or electrode missing.
a. Turn off power supply. Remove shield cup, in-
stall missing parts.
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