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TROUBLESHOOTING & REPAIR | ||
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MOTOR AND TACH FEEDBACK TEST (continued)
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TEST PROCEDURE
1.Remove power from the LF72/LF74 wire drive unit.
2.Using a 5/16 nut driver remove the 5 screws hold- ing the case.
3.Locate the two motor leads and the tach leads See Figure F.1.
4.Apply the correct input voltage (42VAC) to the unit.
5.With the trigger activated and the motor running check for 1VDC min. (210HZ) to 31VDC (1.75KHZ)max. between the black and white motor leads (pins 7 and 8).
6.Check for between 1 and 2 ohms of resistance between the above mentioned leads. Also make sure there is at least 500k ohms of resistance between both leads and the motor shell.
7.With the trigger activated and the motor running check for 5VDC input on the black and red tach leads. Check for .7 VDC to .85 VDC on the black and blue return leads.
8.For further testing on the drive motor you can use an isolated power source and apply between 1 and 31VDC to the leads.
9.If the armature voltage is not present (step 5) and the motor operates normally when an isolated power source is applied (step 8) Control board may be faulty.
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FIGURE F.1 – TACH LEAD LOCATION
TACH |
| BLACK | WHITE |
BLACK |
| LEAD | LEAD |
5 | 6 | 7 | 8 |
1 | 2 | 3 | 4 |
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| TACH | TACH |
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| RED | BLUE |