Lincoln Electric INVERTEC STT Series Service Manual page 77

F-36
6. Test for 25 ohms resistance from lead termi-
nal 401 to terminal 12 on the switch board.
See Figure F.13.
a. If 25 ohms is measured, resistor R4 is OK.
b. If 30 ohms or more is measured, resistor
R4 is faulty and must be replaced.
c. If 20 ohms or less is measured, resistor
R4 is faulty and must be replaced.
Check
Lead 401 to
Terminal 12
Lead 402 to
Terminal 9
Lead 403 to
Terminal 12
Lead 404 to
Terminal 9
> = GREATER THAN
TROUBLESHOOTING & REPAIR
SNUBBER RESISTORS TEST (continued)
FIGURE F.13 - SWITCH BOARD TEST POINTS
401/403
L8441
TABLE F.6 – SNUBBER RESISTORS TEST
Test Result
25 ohms
>30 ohms
<20 ohms
25 ohms
>30 ohms
<20 ohms
25 ohms
>30 ohms
<20 ohms
25 ohms
>30 ohms
<20 ohms
< = LESS THAN
INVERTEC STT
402/404
9
12
SWITCH
7. Repeat the same procedures to test R5, R6,
and R7 according to Table F.6.
8. Reconnect leads 401/403 and 402/404 to the
switch board.
9. Install the case wraparound cover.
Conclusion Next Test Step
OK Continue
R4 open
R4 faulty
OK Continue
R5 open
R5 faulty
OK Continue
R6 open
R6 faulty
OK Continue
R7 open
R7 faulty
F-36
Repair Action
Replace R4
Replace R5
Replace R6
Replace R7