Lincoln Electric SVM112-B service manual Figure F.81 FET Drive Signal

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F-205 F-205

TROUBLESHOOTING & REPAIR

PRE-POWERUP SWITCH BOARD TEST PROCEDURE

FOR REPLACEMENT OF SWITCH ASSEMBLY G2402-2 (continued)

FIGURE F.81 - FET DRIVE SIGNAL

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20V/Div

SNUBBER SIGNAL TEST

1.Adjust the grid for a “light” load.

2.Turn ON the variable AC supply applied to the primary circuit. See Figure F.76.

3.Slowly increase the voltage until the filter capacitor voltage is 25VDC. See Figure F.77.

4.Adjust the grid load to get 5 amps output from the Power Wave. DO NOT PULL MORE

THAN 7-8 AMPS OUTPUT FROM THE POWER WAVE.

5.Set the Oscilloscope for:

5V/div/

20uS/div.

POSITIVE PROBE

R1 12E or 12L

R2 402

R3 12F

R4 404

R5 405

R6 406

R7 12H

R8 408

0 V

20uS/Div

6.Attach the oscilloscope to each of the follow- ing eight test points. Each test point should look like the oscilloscope picture in Figure F.82.

WARNING

ALL METERS AND OSCILLOSCOPES MUST

BE ELECTRICALLY ISOLATED Isolated

Transformer).

NEGATIVE PROBE 401

9E or 9L

403

9F

12G or 12M

9G or 9M

407

9H

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Turn the variable AC primary supply to zero	Once the filter capacitor voltage drops to zero,
volts and then turn it OFF. See Figure F.76.	turn the arc start switch OFF. See Figure F.79.

POWER WAVE 450