Gun Maintenance; Troubleshooting - Miller Gold Seal Model 420 Owner's Manual

4-3. Gun Maintenance

WARNING
FLYING METAL CHIPS AND DIRT can cause injury and damage equipment.
Point gun away from people and in a safe direction when blowing out with compressed air.
3
4
5

4-4. Troubleshooting

WARNING
Welding Trouble
No weld output; wire does not feed.
No weld output; wire does not feed; fan
motor continues to run.
No weld output; wire feeds.
Low weld output.
1 2
6
7
Figure 4-3. Gun Maintenance
Secure power cord plug in receptacle.
Motor fuse F1 open, replace F1.
Replace building line fuse or reset circuit breaker if open.
Secure gun trigger leads or repair leads, or replace trigger switch.
Thermostat TP1 open (overheating). Allow fan to run; the thermo-
stat will close when the unit has cooled.
Connect work clamp to get good metal to metal contact.
Replace contact tip.
Connect unit to proper input voltage or check for low line voltage.
READ SAFETY BLOCKS at start of
Section 4 before proceeding.
Turn Off and unplug unit.
1
Cut welding wire off at contact tip.
Retract wire onto spool and secure.
2
Disconnect trigger leads. Loosen
nut and remove gun and trigger
leads.
3
4
5
6
Disassemble gun as shown.
7
Pull liner from this end. Blow gun
casing out with compressed air.
6
Insert new liner into gun casing until
7
even with end of head tube.
Install collet onto liner.
Install contact tip and nozzle.
Insert gun into feeder and mark
where liner touches drive roll.
Remove gun and cut liner off.
Reinstall gun so that liner is as
close as possible to drive rolls
without touching.
Tools Needed:
Thread welding wire (see Section
3/8, 5/16 in
2-6). Close door.
READ SAFETY BLOCKS at start of
Section 4 before proceeding.
Remedy
swarn10.1 10/91
Wire Spool
Gun Securing Nut
Nozzle
Contact Tip
Head Tube
Liner Collet
Liner
Ref. ST-155 506–A / ST-155 509-A
Section
2-3
4-1B
– –
2-5
4-1A
Figure 3-2
4-3
2-3
OM-174 470 Page 8