OHAUS AV114C, Service Manual

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4-15
CHAPTER 4 TESTING
4.6 TESTING THE AC ADAPTER
The AC Adapters are available with different input voltages. Before testing the Adapter, make sure the
Adapter rating agrees with the power source being used. All Adapters are rated with an output of 12
V ac at 500mA. Adapters can fail by having shorted internal windings producing low voltage output
or no output at all.
1. Plug the AC Adapter in a suitable power source and measure the open circuit voltage on
connector it should be 7 V dc to 17 V ac.
2. Perform procedure Section 3.1.1 or 3.2.1 and remove Top Housing. Plug the AC Adapter
into the scale and measure the voltage at the AC input connector. The output voltage
should be 6 Volts ac minimum, and 14 Volts ac maximum. If the voltage is above this
range, replace the Adapter. If the voltage is below this range, either the Adapter is
defective or the balance is drawing too much current.
4.7 INCAL MOTOR TESTING
This procedure describes how to test the calibration motor.
The InCal Motor receives power from the Main PC board when internal calibration is called for. The
Motor runs on 5 Volts dc and contains an internal potentiometer that is used to determine the motor
position. Figure 4-9 illustrates the wiring diagram of the motor.
To remove the calibration motor, proceed as follows:
1. Remove the balance cover in accordance with procedures in paragraph 3.2.1
2. Disconnect the motor cable from the Main PC board.
3. Refer to Figure 4-9 and apply +5 Volts dc to pin 1 (Brown wire) and -5 Volts dc to pin 2
(Orange wire) for about 10 seconds and note if the motor turns clockwise until it reaches
it's internal stop. Reverse the polarity on pins 1 and 2 and apply 5 Volts dc again for 10
seconds. The motor should run in the opposite direction until the stop is reached. Observe
the calibration mechanism to see if any binding or restrictions occurs. If the motor does not
run, continue with the next step.
CAUTION
DO NOT APPLY POWER TO THE MOTOR LONGER THAN 10 SECONDS AS
DAMAGE CAN BE CAUSED TO A GOOD MOTOR.
4. Perform procedure as described in paragraph 3.2.7 and remove the load Cell.
5. If the motor failed to run, remove the motor and repeat step 3. If the motor runs when free of
the rest of the calibration mechanism, the mechanism might be jammed and requires
replacement or the internal potentiometer in the motor may be defective.
If the motor failed to run in both cases, the motor is defective and should be replaced.