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SQUARE WAVE TIG 255
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F-4
TROUBLESHOOTING & REPAIR
Observe Safety Guidelines
detailed in the beginning of this manual.
TROUBLESHOOTING GUIDE
PROBLEMS
(SYMPTOMS)
The voltmeter reads “00” in Stick
Mode, and there is no output from
the machine when in the TIG
2-Step Mode.
Machine does not respond (no gas
flow, no high frequency and no
open circuit voltage) when arc
switch or amptrol is activated -
displays and fan working. Note:
Machine may have OCV in the
Stick Mode.
POSSIBLE AREAS OF
MISADJUSTMENT(S)
1. Inspect to assure that the arc
start switch is in the on
(closed) position when
welding in the TIG Mode.
1. Machine MUST be in one of
the TIG Modes.
2. The arc start switch or amptrol
may be defective. Check for
continuity between pins “D”
and “E” on cable connector
when arc switch or amptrol is
activated.
RECOMMENDED
COURSE OF ACTION
1. Check for loose connectors at
the SCR bridge and at the
Protection/Snubber board. (J10)
and (J11). See Figure F.2 at
end of this Guide for location.
2. Check the wiring to the Control
Transformer (T2). Observe
directions on decal.
3. The Protection/Snubber board
may be faulty. See
Protection/Snubber Board
Continuity Test.
4. Check the Control Transformer
(T2). See Control Transformer
Voltage Test.
5. Check the polarity switch (S2)
for loose or broken connections.
6. Check the SCR bridge. See
Static and Active SCR Tests.
7. If all previous tests are OK -
then replace the Control board.
1. Check trigger circuit. See Arc
Start Trigger Circuit Test
2. Check the Control transformer
(T2). See Control Transformer
Voltage Test.
3. Protection/Snubber board may
be faulty. See
Protection/Snubber Board
Continuity Test.
4. If all previous tests are OK -
then replace the Control board.
OUTPUT PROBLEMS
If for any reason you do not understand the test procedures or are unable to perform the tests/repairs safely, contact the Lincoln Electric
Service Department for technical troubleshooting assistance before you proceed call 216-383-2531 or 1-800-833-9353.
CAUTION
12/95