Lincoln Electric IDEALARC SP-255 Service Manual page 81

F-28
WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST
4. Test for 2-25 VDC between lead
#539(B) (positive) and lead #541(W)
(negative) to determine if the correct
armature voltage is being supplied.
See Figure F.10.
a. Insert probes into the Molex pin
5. Pull the gun trigger.
6. Read meter. Normal DC volts is from
2 - 25 VDC. VDC varies depending
on wire feed speed.
a. If voltage to the wire drive motor
b. If the wires and plugs are okay
c. If the correct DC armature volt-
d. If the motor is running at high
Test for Supply Voltage to 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 cav-
2. Pull gun trigger.
3. Read meter for 15 VDC.
a. If the 15 VDC is present, check
b. If the leads are okay and 15 VDC
TROUBLESHOOTING & REPAIR
cavities.
armature is zero, check the wires
between Plug J5 and the wire
drive motor. (Check J11, J12 and
J15) See wiring diagram.
and voltage to the drive motor
armature is zero, the Control
Board may be faulty. Replace.
age is present at the wire drive
motor, the motor or motor
brushes may be faulty.
and/or replace.
speed and the armature voltage
is high and uncontrollable, pro-
ceed with the tachometer test.
ities.
the leads to the tach circuit.
is present, the correct voltage is
IDEALARC
being received from the Control
Board. Go to Feedback Test.
c. If the 15 VDC is not present and
the leads are okay, check Plug
J15. The Control Board may be
faulty. Replace.
Test for Feedback Voltage to the Con-
trol Board
1. Test for 1.5 - 3.5 VDC between lead
#555 (positive) and lead #206B (neg-
ative). See Figure F.10 for pin loca-
tions.
a. Insert probes into Molex pin cav-
ities.
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-
Test NING, THE FEEDBACK VOLTAGE MAY
BE FROM 0 TO 5 VDC.
b. If the 1.5 - 3.5 VDC is not pres-
ent or not correct, the Control
Board is not receiving the proper
feedback voltage from the tach
circuit. Check the leads from the
tach circuit to the Control Board
for loose or broken connections.
(Plug J15).
c. If the leads are okay, the tach cir-
cuit may be faulty. Replace.
® SP-255
F-28