Lincoln Electric SVM138-A Service Manual page 75

F-11
TROUBLESHOOTING GUIDE
PROBLEMS
(SYMPTOMS)
The SET voltage is erratic or not
adjustable over the entire range of
control. The actual voltage is also
erratic like the SET voltage.
The field fuse (F101), located on
the power PC board, repeatedly
fails.
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
216-383-2531 or 1-800-833-9353.
TROUBLESHOOTING & REPAIR
POSSIBLE AREAS OF
MISADJUSTMENT(S)
FUNCTION PROBLEMS
1. Check for loose or faulty con-
nections on leads #634, #635,
and #636 between the voltage
control potentiometer (R3) and
the voltage PC board.
1. Make sure the replacement fuse
is a 4/10 amp slow blow type
fuse.
CAUTION
LN-9 GMA Wire Feeder
Observe Safety Guidelines
detailed in the beginning of this manual.
RECOMMENDED
COURSE OF ACTION
1. Remove power to the LN-9
GMA and disconnect Plug J9
from the voltage PC board.
Check the resistance of the volt-
age control potentiometer (R3).
When measured from the wiper
(lead #635) to lead #634, the
resistance should vary smoothly
from 0 to 10,000 ohms when the
shaft is rotated.
2. The voltage PC board may be
faulty. Replace.
1. Perform the T1 Transformer
Test.
2. Disconnect the meter PC board.
If the problem is resolved, the
meter PC board may be faulty.
3. The power PC board may be
faulty. Replace.
F-11