Lincoln Electric PRECISION TIG 375 Service Manual page 60

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Observe Safety Guidelines
detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
The stick electrode "blasts-off"
when touched to the work piece.
NOTE: BEFORE REPLACING A
CONTROL BOARD
If an Advanced Control Panel is
installed, remove it and replace
the Jumper in connector J-3. If
the machine functions normally,
the Advanced Process panel or
harness is defective.
Variable or sluggish welding arc
when welding in the Stick mode.
When Stick Welding the ARC is dif-
ficult to get started.
If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con-
tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed.
Call 1-888-935-3877.
TROUBLESHOOTING & REPAIR
POSSIBLE AREAS OF
MISADJUSTMENT(S)
STICK WELDING PROBLEMS
1. Welding current may be too high
for the electrode size. Reduce
current control setting or use a
larger diameter electrode.
1. Check the work and electrode
cables for loose or poor connec-
tions.
2. The welding cables may be too
small or too long to permit the
desired current to flow.
3. The welding current may be set
too low.
1. Make sure the Stick/TIG switch
is in the Stick position.
2. Make sure the output current
control is set correctly for the
electrode.
CAUTION
PRECISION TIG 375
TROUBLESHOOTING GUIDE
RECOMMENDED
COURSE OF ACTION
1. Perform the SCR Bridge Test.
2. The control board may be faulty.
1. Check the polarity switch for
excessive wear or faulty connec-
tions.
2. Check the interior heavy current
carrying leads and connections.
1. Check the Stick OCV Boost
Circuit. See the Wiring Diagram.
2. Check the OCV Boost Rectifier.
3. Check CR3 and CR2 for proper
operation.
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