OHAUS EB SERIES Service Manual

Contents

OHAUS EB SERIES Service Manual Manual pdf 21 page image

CHAPTER 2 DIAGNOSISEB Series Scales Series Service Manual 2-9 Ohaus Corporation www.ohaus.com2.8 TESTING THE MAIN PC BOARDThe Main PC Board can be tested by measuring voltages and by using a simulator. Thesimulator replaces the Load Cell during testing and is a useful tool for diagnosing problems.2.8.1 Main PC Board Voltage MeasurementsPrior to making the voltage measurements, the battery should have been fully charged andtested.1. Disconnect power from the scale.2. Remove the Top housing, refer to Section 3.1 and leave the Membrane Switchconnected to the scale.3. Disconnect the battery from the Main PC Board.4. Remove screws and washers holding the Main PC Board and lift out the board andlay it flat.5. Connect the AC Adapter to the scale.6. Refer to Figure 2-2, Interconnection Diagram which illustrates the interconnections tothe Main PC Board and is shown as a top view.7. Turn the scale on.8. Using a DVM, measure the excitation voltage across +EXE and -EXE leads it shouldbe 5 volts dc. This is the excitation voltage for the Load Cell and is regulated. If thevoltage is lower, replace the Main PC Board, refer to Section 4.3 and then proceedwith Performance Tests in accordance with Chapter 4.9. Measure incoming power from the AC Adapter connector shown in Figure 2-2. Thevoltage should read above 6 Volts dc with power on.10. Connect the battery to the Main PC Board and measure the voltage across Blackand Red leads on the battery connector. The full battery voltage should read aminimum of 6.0 Volts dc. If the voltage is lower, the battery may require charging or itmay be defective. Refer to Section 2.7 and test the battery.11. Perform simulator testing.2.8.2 Simulator TestingTo perform these tests, the use of a Simulator is required. The basic function of a Simulator is tosimulate the output of a full bridge Load Cell allowing the scale to be separated from the LoadCell for the purposes of troubleshooting and calibration. The Load Cell used in the scale is ratedat 2mV/V output with a 5 Volt excitation voltage applied.