Lincoln Electric PRECISION TIG 375 Service Manual page 58

F-12
Observe Safety Guidelines
detailed in the beginning of this manual.
PROBLEMS
(SYMPTOMS)
High frequency "spark" is present
but weak.
Poor arc starting in the DC TIG
mode.
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)
TIG WELDING PROBLEMS
1. The spark gap may be too large.
Check and reset per instructions
in the Maintenance Section of
this manual.
2. The work and/or torch cables
may be in poor condition allow-
ing the high frequency to "leak"
to ground.
cables, preferably those with a
high natural rubber content and
as short as possible.
3. If helium shielding gas is being
used, reduce the percentage of
helium.
4. Make sure the tungsten elec-
trode is the correct size for the
process.
1. The input line voltage may be
low.
2. Check the torch and work cable
for loose or faulty connections.
CAUTION
PRECISION TIG 375
TROUBLESHOOTING GUIDE
RECOMMENDED
COURSE OF ACTION
1. The high voltage transformer
(T2) may be faulty.
2. Capacitor C6 may be faulty.
3. The high frequency transformer
(T3) may be faulty.
Use good quality
1. Check the J11 plug on the con-
trol board. See Wiring Diagram.
2. Check the back ground resistor
R7.
ohms.
3. Check the background diode
bridge.
F-12
Normal resistance is 20