Drive Assembly Maintenance - Miller Gold Seal Model 420 Owner's Manual

C. Short Circuit Shutdown
If contact tip is shorted and sticks to workpiece, the unit shuts down, but fan runs. To resume operation, release gun
trigger, turn Off unit, and remove contact tip from workpiece. Check contact tip and replace if damaged. Turn On unit to
continue operation.

4-2. Drive Assembly Maintenance

WARNING
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OM-174 470 Page 7
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Figure 4-2. Drive Assembly Maintenance
READ SAFETY BLOCKS at start of
Section 4 before proceeding.
3
7
4
Turn Off and unplug unit.
1 Wire Spool
2 Gun Contact Tip
Cut welding wire off at contact tip.
Retract wire onto spool and secure.
3 Pressure Roll Arm
4 Cotter Pin
5 Pin
6 Screw
7 Bearing
Remove bearing as shown. Install
new bearing and secure with screw.
Reinstall arm onto pin and secure
with cotter pin.
8 Setscrew
9 Smooth Groove For Hard Wire
10 Drive Roll
2
Remove drive roll as shown.
Use a wire brush to clean drive roll.
Push drive roll onto shaft with
desired groove in. Turn drive roll so
one setscrew faces flat side of shaft,
and tighten both setscrews.
11 Knurled Groove For Flux-Cored
Wire
12 Wire Inlet Guide
Remove guide by pressing on
barbed area or cutting off one end
near housing and pulling it out of
hole. Push new guide into hole from
rear until it snaps in place.
Thread welding wire (see Section
2-6). Close door.
Tools Needed:
5/64 in
ST-155 504-A / ST-154 199