4.Test for 2 - 25 VDC between lead #539 (positive) (8J5) and lead #541 (9J5) (negative) to determine if the correct armature voltage is being supplied. See Figure F.8.
a.Insert probes in to the Molex pin cavities.
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 armature is zero, check the wires between Plug J5 and the wire drive motor.
b.If the wires are okay and voltage to the drive motor armature is zero, the Control Board may be faulty. Replace.
c.If the correct DC armature volt- age is present at the wire drive motor, the motor or motor brush- es may be faulty. Test and/or replace.
d.If the motor is running at high speed and the armature voltage is high and uncontrollable, pro- ceed with the tachometer test.
Test for Supply Voltage to Tachometer
1.Test for 15 VDC between lead #515B (positive) (3J5) and lead #206B (negative) (2J5) . See Figure F.8 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) (1J5) and lead #206B (negative) (2J5) . See Figure F.8 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.
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.