Lincoln Electric IDEALARC SP-250 Service Manual page 78

F-31
WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST
Test for Supply
Tachometer
1. Test for 15 VDC between lead
#515B (positive) and lead #206B
(negative). See Figure F. 10 for pin
locations.
a. Insert probes into Molex pin
cavities.
2. Pull gun trigger.
3. Read meter for 15 VDC.
a. If the 15 VDC is present, check
the leads to the tach circuit.
b. If the leads are okay and 15
VDC is present, the correct volt-
age is being received from the
Control Board. Go to Feedback
Test.
c. If the 15 VDC is not present and
the leads are okay, the Control
Board may be faulty. Replace.
Test for Feedback Voltage to the
Control Board
1. Test for 1.5 - 3.5 VDC between lead
#555 (positive) and lead #206B
(negative). See Figure F.10 for pin
locations.
a. Insert probes into Molex pin
cavities.
2. Pull gun trigger.
3. Read meter for 1.5 - 3.5 VDC.
a. If the 1.5 - 3.5 VDC is present,
the tach circuit is sending the
correct feedback signal to the
Control Board.
NOTE: IF THE MOTOR IS NOT RUN-
NING, THE FEEDBACK VOLTAGE MAY
BE FROM 0 TO 5 VDC.
TROUBLESHOOTING & REPAIR
Voltage to
IDEALARC SP-250
b. If the 1.5 - 3.5 VDC is not pre-
sent or not correct, the Control
Board is not receiving the prop-
er feedback voltage from the
tach circuit. Check the leads
from the tach circuit to the
Control Board for loose or bro-
ken connections.
c. If the leads are okay, the Control
Board may be faulty. Replace.
F-31