OHAUS TROOPER, Service Manual

Page: 25 / 70

2-13
CHAPTER 2 DIAGNOSIS
SYMPTOM
Scale can be turned on but
will not calibrate.
PROBABLE CAUSE
Incorrect weights.
The software lock menu is
set ON.(LOC CAL ON)
Load cell assembly defec-
tive.
REMEDY
Verify that proper weights are used.
Set the software lock menu to OFF. Ac-
cess to the software switch is when the
hardware switch is OFF.
Remove the 6 screws from the bottom
cover of the scale. Carefully remove the
platform. Lift the top cover and lay aside
leaving the cables connected to the Main
PC Board.
With the scale plugged in and turned on,
measure voltage on terminals -EXE and
+EXE. The nominal voltage should be 5
V dc. If the voltage is much lower,
disconnect the load cell from the Main
PC Board and measure again. If 5V dc is
present, the load cell may be shorted and
requires replacement.
With the platform in place and the scale
turned on, measure across pins -SIG and
+SIG on the Main PC Board. Typical no
load output from the load cell is -1.0 mv
to + 1.0 mv. If the output exceeds this
value, replace the load cell.
If this measurement is within limits,
place a full load on the platform and
measure again. The difference between
zero and full load reading should be as
shown on the table on the next page. If
the reading is out of this range, replace
the Load Cell. -> Repair Procedures 3.7.
NOTE : Readings may differ from table
due to load cell tolerances.
Reassemble, the scale, perform tests in
Section 5 and verify operation.
TABLE 2-12 TROOPER COUNT SCALE - CANNOT CALIBRATE.