OHAUS TROOPER, Service Manual

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CHAPTER 3 REPAIR PROCEDURES
3. REPAIR PROCEDURES
This section describes how to change individual components of the Trooper Scale and Trooper Count Scale.
When doing this, please refer to the exploded view drawings and parts lists in section 5.
Important: After replacing components, a functional check of the scale must always be carried out.
3.1 REPLACING THE TROOPER SCALE MEMBRANE SWITCH
The membrane switch is affixed to the upper housing of the scale. To replace the membrane switch, the
scale must be disassembled to gain access to the switch connections.
1. Remove power from the scale.
2. Carefully lift and remove the platform from the scale. One rubber foot remains attached to the
platform. This ensures that the platform is properly located on the weighing load cell.
3. Turn the scale over and remove the six screws which hold the upper housing.
CAUTION
Use care in the next step as the membrane switch wiring is attached to the PC board.
4. Place the scale in the upright position and carefully lift the upper housing from the bottom
housing about two to three inches. Reach under the upper housing from the front and carefully
disconnect the flexible cable from connector J5A on the Main PC board.
5. On the upper housing, lift up the defective membrane switch (if necessary carefully prying
it up with a knife) and gently peel it off the upper housing.
CAUTION
Do not use any solvents that may harm the finish or cause damage to the cover.
6. Carefully clean the upper housing membrane switch area (removing all traces of adhesive).
The best method is to use a flat razor blade.
7. Insert the cable from the new membrane switch through the hole in the upper housing. Peel
off the protective film from the new membrane switch and carefully align and affix to the upper
housing.
8. Press the membrane switch down uniformly. Using your fingers with a cloth, roll from the
center of the membrane switch outward towards the edges to remove any air bubbles that may
be trapped.
9. Position the upper housing in place over the scale and connect the flexible cable from the
membrane switch to socket J5A on the Main PC board.
10. Reassemble the scale by replacing the six screws at the bottom of the scale which secure
the upper housing.
11. Replace the platform on top of the scale.