Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 74

F-22
INPUT POWER FACTOR CAPACITOR VOLTAGE CHECK
AND DISCHARGE PROCEDURE (continued)
FIGURE F.1 – POWER FACTOR CAPACITOR DISCHARGE DETAILS
PROCEDURE
1. Remove input power to the machine.
2. With the 5/16" nutdriver, remove the sheet
metal screws that hold the right case side in
place. Remove the right case side.
3. With the volt/ohmmeter, carefully check the
voltage across the input power factor capaci-
tors. When input power is removed, the voltage
across each capacitor should be zero.
(Normally, the capacitors discharge through the
primary winding in the main transformer.)
4. If capacitor voltage is zero, you may begin
working on the Square Wave TIG 355.
5. If any voltage is present, DISCHARGE EACH
INDIVIDUAL CAPACITOR as follows:
TROUBLESHOOTING AND REPAIR
SQUARE WAVE TIG 355
a. Grip the 500 ohm resistor with insulated
gloves and insulated gripping pliers.
b. Hold the resistor across the terminals on
each capacitor for 20 seconds. See Figure
F.1.
c. With the volt/ohmmeter, recheck each
capacitor for voltage.
6. After all the capacitors are discharged com-
pletely, check for broken capacitor leads or an
open primary winding on the main transformer,
which would have prevented the capacitors
from discharging normally.
F-22