Electrical Projects The newest and smallest of the many types of hair dryers is hand-held dryer consisting of a simple circuit employing power switch, safety thermostat, heating elements, and rectifier unit to operate the dc motor. Most problems are in the thermostat or in the blower motor.

The motor operates on approximately 9V dc. The heater is used as a resistor to drop the voltage to approximately 9V ac and feeds the rectifier to produce the 9V, dc. Since motor operation is dependent upon the heater, there is no cool position, only on or off. The air flow is provided by a tangential fan which is quiet and self-cleaning.

A safety thermostat is mounted adjacent to the heater which will open when a higher than normal temperature is reached, such as caused by blocking the inlet or outlet with the hand.


Troubleshooting

When testing through the circuits to discover a defective part, open the soldered connections to isolate the part and obtain a true test. All parts can be cold tested with an ohmmeter.

The heater element can be checked visually. However, with the motor disconnected the safety thermostat will quickly open; a resistance test is more reliable/Since the feed divides the heater element, the two common wires should be disconnected from the cord terminal and each side of the element tested. A resistance reading of 50 ohms or more indicates a good element. Also check the ac feed from the element to the rectifier for a good connection.




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Home > Electrical Projects > Repairs > Hand - Held Dryer

August 20, 2008