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Lincoln Electric IM422 PRO-CUT 40 User Manual

Page 19

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TEST STEPS

Step

1

2

3

Test

FET A1 in circuit
test

Remove leads
4/5 and 1/8 from
Switch PC Board

FET A2 in circuit
test

Remove leads
4/5 and 1/8 from
Switch PC Board

Output Diodes

Check *

Terminals on
Switch PC
Board: 1/8 (pos)
to 12 (neg)

1/8 (neg) to 12
(pos)

Terminals on
Switch PC
Board:

9 (pos) to 4/5
(neg)

9 (neg) to 4/5
(pos)

Remove output
load.

+ work to - elec-
trode

Test Result

>1K ohms

<100 ohms

<100 ohms

>1K ohms

>1K ohms

<100 ohms

<100 ohms

>1K ohms

<100 ohms

>500 ohms

Conclusion

FET OK

Short

FET OK

FET Open

FET OK

Short

FET OK

FET Open

Shorted output
diode (D1 or D2)

Output diodes
OK

Next
Test
Step

4A

4A

4A

4A

Repair Action

Replace
Switch PC
Board

Replace
Switch PC
Board

Replace
Switch PC
Board

Replace
Switch PC
Board

Test individu-
ally

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