Lincoln Electric IM422 PRO-CUT 40 User Manual

Page 20

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Step

Test

Snubber resis-
tors

Snubber diodes

Check *

Disconnect leads
401 thru 404 on
Switch PC
Boards. Measure
across leads:
401 to 12

402 to 9

403 to 12

404 to 9

Disconnect all
leads except
R&W on Switch
PC Board.
Measure across
terminals on
Switch PC
Board:

9 (neg) to 1/8
(pos)

9 (pos) to 1/8
(neg)

12 (neg) to
401/403 (pos)

12 (pos) to
401/403 (neg)

402/404 (neg) to
9 (pos)

402/404 (pos) to
9 (neg)

4/5 (neg) to 12
(pos)

4/5 (pos) to 12
(neg)

Test Result

25 ohms
high resistance

<100 ohms
>1K ohms

>1K ohms
<100 ohms

<100 ohms
>1K ohms

>1K ohms
<100 ohms

<100 ohms
>1K ohms

>1K ohms
<1K ohms

<1K ohms
>100 ohms

>1K ohms
<100 ohms

Conclusion

R4 OK
R4 open

R5 OK
R5 open

R2 OK
R2 open

R3 OK
R3 open

OK
Open

OK
Short

OK
Open

OK
Short

OK
Open

OK
Short

OK
Open

OK
Short

Next
Test
Step

Repair Action

Replace R4

Replace R5

Replace R2

Replace R3

Replace Switch
PC Board