Troubleshooting & repair, External resistance test (leads #21 and #67) – Lincoln Electric NA-5S User Manual
Page 104
F-51
TROUBLESHOOTING & REPAIR
F-51
PROCEDURE
1. Make sure the electrode wire is fed
through the wire contact assembly
tip but NOT touching the "work"
piece.
2. Disconnect input power to the NA-5.
3. Make sure the drive motor cable and
power source control cables are
properly connected to the NA-5 con-
trol box.
4. Using the 5/16" nutdriver open the
control box PC board access door.
5. Locate the TS1 terminal strip. See
wiring diagram.
6. Using the ohmmeter check the resis-
tances per the following table F.2
7. Reconnect the welding cable leads
to the contact assembly.
8. If any of the resistances are not cor-
rect per Table F.2 check the associ-
ated leads, cables and circuits for
"opens" or "shorts". See wiring dia-
gram.
9. Close and secure the control box
access door.
EXTERNAL RESISTANCE TEST (LEADS #21 AND #67)
(Continued)
NA-5
TEST POINTS
EXPECTED
COMMENTS AND
RESISTANCES
CONDITIONS
Lead #667
Zero or less than
Electrode wire must be in
to
1 ohm
contact assembly tip
Electrode wire
Lead #621 to
Zero or less than
Polarity switches must be
work piece
1 ohm
in the correct positions
Lead #667 to
Greater than 15K
Using the 3/4" wrench
#621
ohms
disconnect the welding
cable(s) from the
contact assembly
TABLE F.2 EXTERNAL VOLTAGE SENSING LEADS TEST POINTS