OHAUS CKW-55, Руководство по обслуживанию

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3-5
CHAPTER 3 INDICATOR TESTING
6. Measure the voltage at transistor Q1, pin 2 (location B), it should be 12 V dc, +0.24 V dc. If
this voltage is not present, the Main PB Board must be replaced. Refer to section 4.3 and
replace the Main PC Board.
7. Measure voltage at regulator IC U13, pin 3 (location C), it should be +5 V dc, +0.25 V dc. This
is a supply voltage for the board. If this voltage is above or below this limit, the Main PC Board
should be replaced. Refer to section 4.3 and replace the Main PC Board.
8. Measure the voltage at IC U14, pin 3 (location D), it should be +5 V dc, +0.19 V dc.
This supplies the analog section and the excitation voltage for the external load cell. If this
voltage is above or below these limits, the Main PC Board should be replaced. Refer to section
4.3 and replace the Main PC Board.
9. Measure the voltage at IC U22, pin 2 (location E), it should be 3.6 V dc, +0.14 V dc. This
supplies the operating voltage for the LED displays and bar graph display drivers. If this voltage
is above or below these limits, the Main PC Board should be replaced. Refer to section 4.3 and
replace the Main PC Board.
10.Measure the real time clock battery voltage at (location F), it should be between 3.6 V dc and
2.0 V dc. If lower than 2.0 volts, replace. See section 4.9.
When all voltages are correct, the unit should be tested with a load cell simulator or a known good base.
After replacement, a full operational check should be made in accordance with section 3.9
Figure 3-3. Component Layout Diagram.
3.2.1 Voltage Measurements (Cont.)
A
B
C
D
E
F