TM-716 Page 13MSW And LMSW Series
SECTION 6 − TROUBLESHOOTING
6-1. Troubleshooting Table
. See Sections 6-2, 6-3 and 6-4 for test points and val-
ues and Section 9 for parts location.
. Use Miller Testing Booklet (Part No. 150 853) when
servicing this unit.
. See the Miller Extranet for service memos that may
aid in the repair of this product.
Trouble Remedy
No weld output. Check and replace line fuses or reset circuit breaker. If line fuses or circuit breaker continues to open,
check main transformer T1 and control transformer T2 if applicable.
For 220 V models effective with Style No. JA41, check fuse F1, and replace if necessary (see Section
7-2).
Check continuity of input power cord and plug PLG1, and replace if necessary.
Check continuity of interconnecting cord, and replace if necessary.
Check continuity of Power switch S1, and replace if necessary.
Check continuity of start switch PB1, and replace if necessary.
Check coil voltage and connections of contactor W. Check continuity of coil and condition of contacts.
Replace W if necessary.
Check main transformer T1 for signs of winding failure. Check continuity across winding, and check for
proper connections. Replace T1 if necessary.
For 220 V models, check control transformer T2 for signs of winding failure. Check continuity across wind-
ings, and check for proper connections. Replace T2 if necessary
No weld output; input line circuit
breakers or fuses trip or blow repeatedly.
Possible internal short-circuit. Check bottom tong clamp insulation (2 pieces − see Section 9, Parts List)
for cracks or arc tracks. Replace insulation if necessary.
Possible internal short-circuit. Check main transformer insulation (2 pieces − see Section 9, Parts List)
for cracks or arc tracks. Replace insulation if it is burned through or worn.
Low weld output. Dress or replace tips (see Section 3-1).
Check tip threads. Replace tips if necessary (see Section 3-1).
Remove and clean tongs. Remove insulator plugs from front housing, and blow out tong holders with com-
pressed air (see Section 3-2).
Clean ends of tongs and tong holders (see Section 3-2).
Check Power switch S1 contacts for pitting and wear. Replace S1 if necessary.
Check start switch PB1 contacts for pitting and wear. Replace PB1 if necessary.
Check contactor W contacts for pitting and wear. Replace W if necessary.
Check tong braid for loose connections, fraying, or overheating. Replace tong braid if necessary.
Longer than normal weld time required. Dress or replace tips (see Section 3-1).
Clean workpieces.
Adjust tong pressure (see Section 3-3).
Clean ends of tongs and tong holders (see Section 3-2).
Check input line voltage.
Check contactor W contacts for pitting and wear. Replace W if necessary.
Burn through at point of weld. Shorten weld time.
Adjust tong pressure (see Section 3-3).
Dress or replace tips (see Section 3-1).
Realign tips (see Section 3-2).
Tips overheating. Not enough tong pressure. Increase tong pressure.
Weld time too long. Reduce weld time.
Material too thick for the spot welding machine.
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