Lincoln Electric LN-25 PRO DUAL POWER Service Manual page 64

F-14
DRIVE MOTOR AND TACH FEEDBACK TEST (continued)
CONTROL BOX
ASSEMBLY
PROCEDURE
1. Remove power from the LN-25™ PRO DUAL
POWER wire drive unit.
2. Perform Case Cover And Control Box
Removal Procedure.
3. Using a 5/16" nutdriver remove the four screws
securing the control box cover. Locate the two
motor leads and the 3 tach leads. See 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).
6. Check for 1.5 ohms of resistance between the
above mentioned leads. Also make sure there
is at least 550k ohms of resistance between
both leads and the motor shell.
TROUBLESHOOTING AND REPAIR
FIGURE F.3 – CONTROL BOX ASSEMBLY
LN-25™ PRO DUAL POWER
7. With the trigger activated and the motor running
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.
NOTE: If the tach feedback is missing the
board will limit the motor voltage to
10VDC no matter where the w/s poten-
tiometer is set.
9. If all the above voltages are not present, your
motor or tach needs to be replaced. See Wire
Drive Motor and Gear Box Replacement
Procedures.
F-14
CASE COVER