Lincoln Electric SVM127-A service manual Tach Feedback Test Procedure

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F-33 F-33

TROUBLESHOOTING & REPAIR

WIRE DRIVE MOTOR AND TACH FEEDBACK TEST (continued)

FIGURE F.7 – LEADS #525, #510, #555 ON CONTROL PC BOARD

LEAD LEAD LEAD

525 510 555

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TACH FEEDBACK TEST

PROCEDURE

1.Locate tach PC board leads #510, #525 and #555 on the control PC board. See Figure F.7.

2.Check leads #525(+) to #510(-) for the pres- ence of 15VDC. This is the supply voltage from the control PC board to the tach PC board. If the voltage is present, proceed to the next step. If the voltage is missing, check the wiring and perform the General

Power Supply Test.

3.With gun trigger activated or the gun termi- nals jumpered together (see the Wiring Diagram), check leads #555(+) to #510(-) for the presence of between 4.5 - 10.5VDC. (The motor must be running). This is the feedback voltage from the tach PC board to the control PC board. This voltage is depen- dent upon motor speed.

If the feedback voltage is missing or does not vary with motor speed, the tach PC board may be faulty.

4.After the wire drive motor and tach feedback tests are completed, remove the jumper from the gun terminals (if used) and close the left case side cover assembly and re- attach the screws.

LN-9 Wire Feeder