HEIDENHAIN iTNC 530 Service Manual page 361

Principle of the key The keys are evaluated via a matrix. Every key is located above a crosspoint of SL (= scan line)
and RL (= return line). --> see "Key Matrix of the Keyboard Units" on page 22 – 367 or see "Key
matrix
Matrix of the Keyboard Units" on page 22 – 382.
Is a line (cable,
board) or the key
defectibe?
May 2006
Inspection of the keyboard
Use the key matrix to find a key that is
selected by the same RL line as the
defective key (and which functions in
the selected operating mode).
Press this key.
Any reaction?
Yes
Use the key matrix to find a key that is
selected by the same SL line as the
defective key (and which functions in
the selected operating mode).
Press this key.
Any reaction?
Yes
The matrix lines (keyboard cable,
keyboard PCB) are in order.
The contact of the key is
probably defective.
No
The line to the matrix is interrupted.
Check the keyboard cable (measure
the cable, try replacement, etc.)
and the connectors.
Is the keyboard PCB defective?
No
22 – 361