Lincoln Electric INVERTEC POWER WAVE 450 SVM112-B Service Manual page 265

F-205
PRE-POWERUP SWITCH BOARD TEST PROCEDURE
FOR REPLACEMENT OF SWITCH ASSEMBLY G2402-2 (continued)
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.
F.77.
4. Adjust the grid load to get 5 amps output from
the Power Wave.
THAN 7-8 AMPS OUTPUT FROM THE
POWER WAVE.
5. Set the Oscilloscope for:
5 V/div/
20 uS/div.
POSITIVE PROBE
R1
R2
R3
R4
R5
R6
R7
R8
Turn the variable AC primary supply to zero
volts and then turn it OFF. See Figure F.76.
TROUBLESHOOTING & REPAIR
FIGURE F.81 - FET DRIVE SIGNAL
20V/Div
See Figure
DO NOT PULL MORE
12E or 12L
402
12F
404
405
406
12H
408
POWER WAVE 450
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
Transformer).
NEGATIVE PROBE
401
9E or 9L
403
9F
12G or 12M
9G or 9M
407
9H
Once the filter capacitor voltage drops to zero,
turn the arc start switch OFF. See Figure F.79.
F-205
Isolated