Avery Berkel CX20 SERIES, Service Manual

Page: 163 / 353

14 — Keyboard
14–3 CX20/CX30/CX34 Service Manual
Figure 14.1 Keyboard
WARNING
TACTILE MEMBRANE SWITCHES CAN
BE EASILY DAMAGED UNTIL FIXED TO A
RIGID BACKING. DO NOT OPERATE
UNLESS LYING ON A FLAT SMOOTH
SURFACE. TAKE CARE NOT TO BEND
MEMBRANE IN SWITCH AREAS WHEN
REMOVING BACKING PAPER AND
FIXING IN POSITION.
Keyboard surface
Warning label
Backing paper (protecting
self–adhesive material)
Earth strap
Ribbon cable
(acetate)
14.1 Description
The keyboard is a tactile type having 69 (CX20), 125 (CX30) or 80 (CX34) key
positions. Each key position is at an intersection of the lattice. The keyboard is
mounted on the unit case at the vendor side of the unit.
The keyboard is connected to the main PCB of the unit by a flying connector.
The keyboard end of the flying connector is an acetate ribbon cable terminated
in a 24–pin male flying connector. The main PCB also has a ribbon cable,
encircled by a ferrite core (for spike suppression), terminated by a 24–pin female
flying connector. The keyboard has an earth strip which is connected to the
inside of the cover (CX20/CX30) or front housing (CX34) behind the keyboard;
from there an earth lead is connected to the base of the machine.
Pressing a key position causes two of the metal laminates to contact each other.
Keyboard operation is tactile, given by the ‘oil can’ key operation. The keyboard
is strobe–scanned electronically to detect key depression: the scanning source
is the same scanning source as that which scans the unit display.
The keyboard is self–adhesive and, if removed from the unit case, will be
damaged beyond further use. Do not attempt to operate the keys of a keyboard
which is not fitted to a unit: to do so will distort permanently the laminates of the
keyboard and make it unfit for further use.