TOC

F-30

TROUBLESHOOTING AND REPAIR

F-30

 

WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST (continued)

 

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TEST FOR FEEDBACK VOLTAGE TO CONTROL BOARD

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

2.Locate plug J1 on the control PC board.

3.Locate the following leads on plug J1 (see Figure F.9):

 

PLUG

LEAD

LOCATION

 

 

555

6J1

206B

1J1

 

 

4.Connect main input power to the machine.

5.Make the following voltage tests:

a.Turn the machine OFF between each test.

b.Carefully insert the meter probes into the back of each Molex plug pin cavity.

gun trigger to conduct the voltage test.

FROM

TO

EXPECTED

LEAD

LEAD

VOLTAGE

 

 

 

555

206B

1.5 to 3.5 VDC

(6J1)

(1J1)

 

 

 

 

6.If the 1.5 to 3.5 VDC is present, the tachometer circuit is sending the cor- rect feedback signal to the Control PC Board.

7.If the 1.5 to 3.5 VDC is not present or not correct, the Control PC Board is not receiving the proper feedback voltage from the tachometer circuit. Check the leads from the tachometer circuit to the control PC board for loose or broken connections.

8.If the leads are okay, the tachometer circuit may be faulty, replace the tachometer circuit.

9.Replace the tool tray.

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c. Turn the machine ON and pull the

POWER MIG 255C

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Lincoln Electric SVM170-A service manual Test for Feedback Voltage to Control Board, 555 206B To 3.5 VDC 6J1 1J1