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OM-880 Page 19
SC-112 013-A
Voltage Control
Board PC4
Wiring Harness Plug
Standoff
Support (4)
Contactor Control
Board PC3
Wiring Harness Plug
Standoff Support (3)
Figure 6-1. Circuit Board Locations And Components
CAUTION: ELECTROSTATIC DISCHARGE
(ESD) can damage circuit boards.
• Put on properly grounded wrist strap
BEFORE handling circuit boards.
• Transport circuit boards in proper static-
shielding carriers or packages.
• Perform work only at a static-safe work area.
INCORRECT INSTALLATION or misaligned
plugs can damage circuit board.
• Be sure that plugs are properly installed and
aligned.
EXCESSIVE PRESSURE can break circuit
board.
• Use only minimal pressure and gentle move-
ment when disconnecting or connecting
board plugs and removing or installing board.
IMPORTANT: All directions, such as left or right, are
with respect to the serviceperson facing the front panel.
1. Open necessary side door as follows: left side for
Contactor Control board PC3, or right side for
Voltage Control board PC4.
2. Disconnect wiring harness plug from board re-
ceptacle (see Figure 6-1), and remove board
from standoff supports.
3. Reconnect wiring harness plug to new board re-
ceptacle; be sure plug snaps firmly in place.
4. Install and secure new board onto standoff sup-
ports on lower front panel.
5. Close side door.
6. Resume operation.
6-4. TUNGSTEN ELECTRODE (Table 6-2, And
Figures 6-2 And 6-3)
Use Table 6-2 to select the correct size and type tung-
sten electrode. Prepare the tungsten electrode using
the following guidelines. A properly prepared tungsten
electrode is essential in obtaining a satisfactory weld.
A. For AC or DC Electrode Positive Welding (Fig-
ure 6-2)
Ball the end of tungsten electrodes used for ac or dc
electrode positive welding before beginning the welding
operation. Weld amperage causes the tungsten elec-
trode to form the balled end. The diameter of the end
should not exceed the diameter of the tungsten elec-
trode by more than 1-1/2 times. For example, the end of
a 1/8 in. (3.2 mm) diameter tungsten electrode should
not exceed a 3/16 in. (4.8 mm) diameter end.