OHAUS TROOPER, Service Manual

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3-6
CHAPTER 3 REPAIR PROCEDURES
3.4 REPLACING THE TROOPER COUNT SCALE MEMBRANE SWITCH
The membrane switch is affixed to the upper housing of the scale. The scale must be disassembled to gain
access to the membrane 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 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.
One screw is located underneath the rear most sealing cover. The cover screw will have to be
removed first.
CAUTION
Use care in the next step as the membrane switch wiring is attached to the PC board.
4. Place the scale 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 three flexible cables from the Main PC board. Two cables are part of the
membrane switches and the other cable is for the display 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 two cables from the membrane switch through the hole in the upper housing. Peel
off the protective film from the new membrane switch and carefully 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 two flexible cables from
the membrane switch to connectors J2 and J3 on the Main PC board and the single cable from
the display PC board to connector J4 on the Main PC board.
10.Reassemble the scale.
11.Replace the platform on top of the scale.