Replacing The Display Mounting Plate, Display Unit And Digital Pcb - KERN FTB Service Manual

5.7

Replacing the display mounting plate, display unit and digital PCB

The display mounting plate is located underneath the keypad membrane and is attached to the scale housing by 6 snaps. The
display unit comprises the digital PCB, the liquid crystal display (LCD) and the backlighting unit. It is held in place on the
mounting plate by snaps. The digital PCB is connected to the analog PCB and the RS232C interface by two ribbon cables.
5.7.1 Preliminary word
• Unscrew the adjustable feet and remove them.
• Undo the bottom plate retaining screws, removing them and the plate itself.
• Remove both EMC clamps. Undo the red retaining screw (since September 2005) which fastens the display unit to the
mounting plate. Pull back the front cantilever snaps holding the display unit to release it, raise the front edge of the
display unit and withdraw it from the rear snaps. Disconnect the RS232 cable and the connecting cable to the analog PCB
from the digital PCB. Remove the display unit.
5.7.2 Replacing the display mounting plate
Note: In order to replace the display mounting plate, the keypad overlay must be removed. This cannot then be reused and
must also be replaced.
• Remove keypad overlay (Chapter 5.2).
• Push the 3 cantilever snaps at the front edge of the display mounting plate backwards to release the plate and remove it to
the outside.
• Insert the new display mounting plate into the aperture so that it clicks into place.
• Apply the new self-adhesive keypad overlay (Chapter 5.2).
5.7.3 Replacing the liquid crystal display (LCD) or the backlighting unit
• Place the display unit with the digital PCB downwards on a conductive CMOS film.
• Disconnect the backlighting ribbon cable from the digital PCB.
• Carefully insert a flat blade screwdriver (size 4) between the digital PCB and the backlighting unit immediately adjacent to
the connectors.
• With the screwdriver pry the liquid crystal display and the backlighting unit out of the socket strips. When doing this, lever
the shaft of the screwdriver against the edge of the digital PCB. Never lever the tip of the screwdriver against the surface of
the PCB, as this could damage the latter!
• Remove the upper protective film of the backlighting unit.
• Place the new backlighting unit onto the digital PCB (it snaps into place on the board).
• Remove the upper and lower protective cover of the LCD.
• Carefully place the LCD onto the backlighting unit and ensure that the connector pins are correctly aligned with the socket
strips. When correctly positioned, the ends of the LCD and backlighting unit are flush. Use a flat object such as a ruler to
exert a uniform pressure on the LCD and gently push it home.
• Push the backlighting unit ribbon cable connector onto the digital PCB pins.
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