Service manual

PT300, Service Manual
Rev B, October, 2000
30
Remove and replace load cell
Tools required
Twenty thousand pound calibration press.
8" x 8" x 2 ± .25” aluminum loading block.
8" x 8" x 0.5" rubber loading pad.
Static dissipation station for any P.C. board work.
#2 Phillips screwdriver for bezel and board mounts.
Torque wrench covering 12 ft-lbs.
Torx T30 bit.
Small slotted blade screwdriver.
Locktite 242 removable Threadlocker (BLUE).
Torque-seal potentiometer shaft sealer.
Dow-Corning 3145 electronic grade RTV Adhesive/Sealant.
Soldering iron and solder.
Caution:
The following procedure must be performed at a static controlled workstation. The
main printed circuit board is subject to damage by electrostatic discharge.
Disassembly
1) Remove all 10 bezel screws.
2) Detach keyboard assembly and set aside. Do not unplug keyboard.
3) Remove 2 screws holding circuit board.
4) Remove main circuit from housing.
5) Unplug wire harness, set board and keyboard aside.
6) Peel insulator from back of summing board.
7) Record connection and color code of cell to be removed.
8) Unsolder loadcell leads from summing board.
9) Rotate summing board until potentiometer is accessible.
10) Remove 4 bolts holding platform.
11) Remove platform.
12) Remove 2 bolts holding load cell to platform.
13) Pull lead from load cell through hole in case.
14) Remove old loadcell from cavity.
15) Clean all old RTV from load cell lead feed-through hole.