Lincoln Electric INVERTEC STT Series Service Manual page 88

F-47
FROM PROTECTION
BOARD OVERVOLTAGE
T1 AUXILIARY
TRANSFORMER
3J31
#503A
2
4
V
A
C
2J31
7. Using the ohmmeter check for continuity (zero
ohms) from plug J31 pin 3 (lead#503A) to plug
J4 pin 6 (lead#210).
Simplified Trigger Circuit Diagram.
8. If any of the resistance checks are abnormal-
ly high in steps 5, 6 or 7, check for broken or
loose wires, connections or "open" ther-
mostats. Also check the small inductors on
the Remote Protection Board.
F.22, Simplified Trigger Circuit Diagram.
ELECTRIC SHOCK can kill.
TROUBLESHOOTING & REPAIR
TRIGGER CIRCUIT TEST (continued)
FIGURE F.22 – SIMPLIFIED TRIGGER CIRCUIT DIAGRAM
POWER BOARD
#301
7J6 11J4
#305
2J6 3J4
PWM
OUTPUTS
TO POWER
BOARD
STT II Only
#379
#224
#210
6J4
6J22
TO
5J4
POWER
BOARD
#212
12J4
See Figure F.22,
See Figure
WARNING
• With input power ON, there
are high voltages inside
the machine. Do not reach
into the machine or touch
any internal part.
INVERTEC STT
CONTROL BOARD
P
W
M
#223
9J4 8J33
6J34
#212C
9. Apply the correct input power to the machine
and turn ON.
10. Locate plug J6 on the power PC board. See
Figure F. 15. in the Power Board Test.
11. Carefully check for approximately 1VDC from
plug J6 pin 2 (lead #305)(+) to plug J6 pin 7
(lead #301) (-). If the approximately 1VDC is
present the power PC board and protection
PC board are functioning properly for the trig-
ger circuit to operate. If the correct DC volt-
age is NOT present, perform the Protection
Board Test and the Power Board Test.
12. Test to make sure the T1 auxiliary transformer
is producing 24VAC.
Simplified Trigger Circuit Diagram.
13. If the above tests do not reveal the problem,
the control PC board or associated wiring
may be faulty. See Figure F.22, Simplified
Trigger Circuit Diagram.
REMOTE
PROTECTION
BOARD
14 AMPHENOL
3.5 ohms
#413
13J36 C
3.5 ohms
#405
5J36 D
See Figure F.22,
DEC 97
F-47