Service manual

PT300, Service Manual
Rev B, October, 2000
41
1) It is assumed that the scale is disassembled with the main circuit board
removed from the case (but still plugged in) and sitting on an insulating
surface. The keypad must be plugged into the main circuit board.
2) On the keypad, press the Local/Total and the lb/kg and while holding
them down turn the scale on and release all switches. The scale should
turn on with a number other than zero, we call this number the "raw
counts", ideally this number should be between 1500 and 4500. The
raw counts should change as weight is applied to the platform, (even a
small weight of 5 or 10 pounds should register a change) it will either
increase or decrease depending on the signal coming from the load
cells.
3) If the raw counts are lower than 1500 or go down as weight is applied it
means that the negative signal is too high and needs to be lowered
(lowering the negative signal will increase the displayed raw counts).
Place a shunt in position 2 of JP1 and using trial and error place another
shunt in position 5, 6 or 7 whichever puts the displayed value between
1500 and 4500.
4) If the raw counts are higher than 4500 and go up as weight is applied it
means that the positive signal is too high and needs to be lowered
(lowering the positive signal will decrease the displayed raw counts).
Place a shunt in position 1 of JP1 and using trial and error place another
shunt in position 5, 6 or 7 whichever puts the raw counts between 1500
and 4500.
5) Deadload adjustment complete.