Lincoln LT-7 Troubleshooting Manual page 16

B-7
Troubleshooting Guide –
components. See Wiring Diagrams for troubleshooting of specific circuits.
PROBLEMS
(SYMPTOMS)
The wire will NOT inch down but
does inch up properly.
When the start switch is pressed
the wire feeds down properly.
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 electrical technical troubleshooting assistance before you proceed.Call 216-383-2531 or 1-800-
833-9353
TROUBLESHOOTING AND REPAIR
See Wiring Diagrams for location of specified
FIELD
COURSE OF ACTION
FUNCTIONAL PROBLEMS
1. While pressing the inch down
switch observe light 2J. It
should be lit. If not the inch
down switch (S4) or associated
wires may be faulty. See wiring
diagram.
2. If the LT7 is in the constant volt-
age (CV) mode and light 2J
does light then the logic board
may be faulty.
LT-7 TRACTOR
RECOMMENDED SHOP
COURSE OF ACTION
1. If the LT7 is in the variable volt-
CAUTION
Observe Safety Guidelines
detailed in the beginning of this manual.
age (VV) mode, and a variable
voltage board is installed, dis-
connect lead #21 from the ter-
minal strip. Turn on input power
and while pressing the inch
down switch observe light 3A. If
light 3A does NOT light the vari-
able voltage board may be
faulty. Replace board and
reconnect lead #21.
If light 3A does light, with lead
#21 disconnected, the resis-
tance across leads #21 and
#67 is too low. The resistance
must be above 500 ohms. The
low resistance could be caused
by the following:
• A lead or object external to
the power source or LT7
causing a low resistance
between leads #21 and #67.
• A non-Lincoln power source
not designed with the
required impedance.
• A defective power source.
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