Lincoln Electric PRECISION TIG IM936 - Manual (Page 36)

E-5 TROUBLESHOOTING E-5
PRECISION TIG 375
Observe all Safety Guidelines detailed throughout this manual
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact your Local
Lincoln Authorized Field Service Facility for technical troubleshooting assistance before you proceed.
CAUTION
PRESET & OUTPUT CONTROL PROBLEMS
PROBLEMS
(SYMPTOMS)
POSSIBLE AREAS OF
MISADJUSTMENTS
RECOMMENDED
COURSE OF ACTION
Meter does not display preset
High output current in both DC & AC
polarities regardless of preset
High output current in DC polarity
regardless of preset, o.k. in AC polar-
ity
In 2-step Tig, output stays on for
more than downslope time after trig-
ger open (machine with Advanced
Control panel only)
Output stays on after releasing
hand/foot Amptrol (machine with
Advanced Control panel only)
1. Faulty potentiometer R1 or its con-
nection
2. Bad connection at P9 of Control
PC board
3. Faulty Advanced Control PC board
( if present ) or its connection to
the main Control PC board
4. Missing plug P3 on Control board
or bad connection at P3 when an
Advanced Control PC board is not
present
1. Bad connection at P6 of Control
PC board
2. Bad shunt connection
3. Faulty Control PC board
4. Faulty SCR bridge
1. Shorted free wheeling diode D1
1. Bad 2/4 step switch or its connec-
tion
2. Bad connection at P1 of Advanced
Control PC board
1. Downslope is not set at min.
2. Bad Downslope potentiometer
R12 or its connection
If all recommended possible areas
of misadjustment have been
checked and the problem persists,
Contact your local Lincoln
Authorized Field Service Facility.