Lincoln Electric SVM157-A service manual Test for Supply Voltage to Tachometer

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F-17 TROUBLESHOOTING AND REPAIR F-17

WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST

(continued)

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5. Make the following voltage tests:

WARNING

ELECTRIC SHOCK can kill.

•Do not touch electrically live parts such as output terminals or internal wiring.

•All input power must be electri- cally disconnected before pro- ceeding.

a.Turn the machine OFF between each test.

2.Locate plug J4.

3.Locate the tach leads on plug J4. See

Figure F.5.

4.Connect the main input power to the machine.

5.Make the following voltage tests:

WARNING

ELECTRIC SHOCK can kill.

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b. Carefully insert the meter probes into the lead side of plug J4. See Figure

F.4.

c. Turn the machine ON and pull the gun trigger to conduct the voltage test.

FROM LEAD FROM LEAD FROM LEAD

Black	White	2-29 VDC
Armature	Armature	(varies depend-
Lead	Lead	ing on wire feed
		speed)

6.If the voltage to the wire drive motor arma- ture is zero, check the wires between plug J4 and the wire drive motor. Also check the electrical connector J5 for proper con- nections and jumper plug. See the Wiring Diagram.

7.If all wires and connectors are good and the voltage to the drive motor armature is zero, the control PC board may be faulty. Replace the control PC board.

8.If the motor is running at high speed and the armature voltage is high and uncon- trollable, Proceed with the tachometer test.

TEST FOR SUPPLY VOLTAGE TO TACHOMETER

1.Disconnect the main AC input power to the machine.

•Do not touch electrically live parts such as output terminals or internal wiring.

•All input power must be electri- cally disconnected before pro- ceeding.

a.Turn the machine OFF between each test.

b.Carefully insert the meter probes into the lead side of plug J4.

FROM LEAD FROM LEAD FROM LEAD

Black (-) Red (+) 5-6 VDC

6.If the 5-6 VDC is present, check the leads to the tachometer circuit.

7.If the leads are okay and 5-6 VDC is pre- sent, the correct voltage is being received from the control PC board. Continue with the supply voltage to tachometer test.

8.If the 5-6 VDC is not present and the leads are okay, the control PC board may be faulty, replace the control PC board. Also check plug J5 and the jumper plug. See Wiring Diagram.

POWER MIG 200