CHAPTER 3 MAINTENANCE PROCEDURESPioneer™ Balance Service Manual 3-13 Ohaus Corporation www.ohaus.com3.3.9 Position Sensor Board Removal/Replacement/Adjustment – PrecisionIf the Position Sensor Board is defective and requires replacement, proceed as follows:1. Open the balance, and remove the Load Cell.2. Un-solder the wires that attach tothe Position Sensor Board. The 3-wire Ribbon Cable is connected tothe Contact Board. The two whitewires at the top are thermistorwires: polarity is not important. Thetwo wires at the bottom-right mustbe placed back in their originalposition. (See Figure 3-33.)Figure 3-33. Position Sensor Board.3. Remove the three screws holding the Position Sensor Board in place.(The two on the right have washers. The one on the left doesn’t.)4. Remove the Position Sensor Board, and install the replacement. Insert all screwspreviously removed. Tighten the screws finger-tight to allow adjustment in Step 9.5. Re-solder all wires. (See Figure 3-33.)6. Place the Load Cell in position and mount it with one screw.7. Connect the cable from the Main PCB to the Position Sensor Board.8. Operate the balance with the Weighing Pan in its normal position, but with the topcover off. Power on using the middle button on the PCB.NOTE:The Position Sensor Board contains an Optical Sensor which must be positioned inthe Ratio Beam’s center of travel for the balance to function properly.9. Adjust the vertical position of thePosition Sensor Board: if it is toohigh or too low, the displayindicates Error 8.X.(See Figure 3-34.) Move it until thedisplay indicates other than 8.X. Ifthere is an IDNR error, fix this errorfirst, and then check that an Error8.X is not displayed.10. Tighten the screws on the PositionSensor Board. (See Figure 3-35.)Figure 3-34. Adjust position of Sensor Boarduntil Err8.X does not appear.Note: A 2.5mm Allen Key can be cut to fit thespace between the Housing and the PositionSensor Board.3-wire RibbonCableWhite, RedThermistor cables
