Electrical Projects With the development of sealed-cell rechargeable batteries and miniaturized chargers, a large number of appliances have come to be known as "cordless." When these appliances malfunction, the problem is usually low battery voltage. See Chapter 2 for a discussion of chargers and charging techniques. We will use Disston's grass shears as a representative example of this class of appliances.


Troubleshooting

The shear runs below normal speed. Check the charger output with a VOM. The reading should be between 2.3 and 3.6V. If not, replace the charger since repairs are impractical. Next, check the battery pack by putting it on charge overnight. If the shear still does not develop normal speed and power, replace the battery pack. Remove the terminal assembly from the shear and inspect for bad or intermittent connections. There should be a potential of 10V between the positive and negative terminals. Wiggle the terminals as you make the reading. No voltage means that the wiring is broken and needs replacement.

The shear operates for only a short period (less than 45 minutes) between charges. The first thing to look for is binding in the mechanism which would cause the motor to draw more current. Remove the blades and check for any deflection or obstruction in the gear teeth. Check to make certain the blades are not set too close together. The upper blade teeth should barely contact the lower blade teeth. With the blade mechanism installed, the motor should draw between 1.4 and 2A. Replace the blade assembly if the mesh is off, the blades are dull, or the meter reading fails to stay within specifications.




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Febuaury 10, 2012