Lincoln Electric LN-25 SVM179-B Service Manual page 60

F-16
DRIVE MOTOR AND TACH FEEDBACK TEST (CONTINUED)
CASE
PROCEDURE
1. Perform the Case Removal Procedure.
2. Remove the 5 #10-24 x .50 screws holding
the control box cover to access the contactor
leads. See Figure F.2.
3. Remove the 5 #10-24 screws holding the con-
trol box cover, and locate the two motor leads
and the 3 tach leads See the Wiring
Diagram.
4. Apply the correct input voltage (15-110vdc) to
the unit.
5. With trigger activated and the motor running
check for 2.6VDC min. to 32VDC max.
between the black and white motor leads
(pins 7 and 8).
NOTE: If the tach feedback is missing the board
will limit the motor voltage to 10VDC no
matter where the w/s pot is set.
TROUBLESHOOTING & REPAIR
FIGURE F.4 – CONTROL BOX ASSEMBLY
CONTROL BOX ASSEMBLY
LN-25™ PRO
6. Check for 1.5 ohms of resistance between the
black and white leads. Also make sure there
is at least 550k ohms of resistance between
both leads and the motor shell.
7. With the trigger activated and the motor run-
ning check for 15.6VDC input on the black
and red tach leads. Check for 6.2vdc at any
speed or ≈72hz (min.). to ≈1.2Khz (max). on
the black and blue return leads.
8. For further testing on the drive motor you can
use an isolated source and apply between
2.6VDC and 32VDC to the motor leads.
9. If all the above voltages are not there the
motor or tach needs to be replaced. See Wire
Drive Motor and Gear Box Removal and
Replacement.
F-16