Lincoln Electric CLASSIC I SVM134-A Service Manual page 60

F-16
Shunt Coil and Series Coil Resistance Tests
7. Turn the engine OFF.
8. Using the 3/8" nut driver, disconnect the two
leads from the left side brush holder. See
Figure F.3. Separate the two leads. One
will be a larger "solid" lead (series coil).
The other will be a smaller flex lead (shunt
coil).
9. Using the 3/8" nut driver, remove the two
flex leads from the right side brush holder.
Note lead placement for reassembly.
Using the volt/ohmmeter, check the shunt
coil resistance. Check from the left side
small flex lead to the right side white flex
lead. See Figure F.3. Normal resistance is
120 - 130 ohms. If the resistance is very
high or "open," the shunt coils are faulty.
Replace them. If the resistance is very low,
the shunt coils are "shorted."
them.
Also measure the resistance from either
lead to machine ground. This resistance
should be very high - at least 500,000
ohms.
TROUBLESHOOTING & REPAIR
DC EXCITER TEST (continued)
FIGURE F.3 – BRUSH HOLDER LEADS
SMALL
FLEX
LEAD
Replace
CLASSIC I
WARRANTY
WHITE
FLEX
LEAD
SOLID
LEAD
10. Using the volt/ohmmeter, check the series
coil resistance.
a. Check from the larger solid lead (left
side) to the 120VDC receptacle. (Check
at the longer slot opening. See Figure
F.1. ) Normal resistance is less than 1
ohm.
b. Also measure the resistance from the
solid lead (left side) to machine ground.
See Figure F.3. This resistance should
be very high - at least 500,000 ohms. It
may be necessary to disconnect the
series coil from the 120VDC receptacle
to isolate the series coil from the rest of
the circuitry. See the Wiring Diagram.
11. If the shunt and series coils are good, and
the exciter is not operating properly, the
exciter armature may be faulty. Replace the
exciter armature.
12. After the test and repairs are completed,
install the exciter cover using the 3/8" nut
driver.
F-16