"John-Del" wrote in message
...


Assuming that it's one of the tactile 'dome' switches, it is very common
for
these to 'collapse' and effectively fail short circuit. I know that you
said
you were not looking to repair it, but it really is a very simple fix if
you
can be bothered to take it apart.

Arfa

He said it wasn't collapsed, although there's the possibility some liquid
was spilled in the key matrix and is causing an unintended function
command.

But I've seen a few of these over the years where the scan lines can be
unsoldered at the micro for a test and the fault remains. Sometimes it's
a bad micro caused by a static discharge through the control board.




I had a piano keyboard once that had lost some notes.
It turned out the scan IC scanned both the keys and the button/LED matrix
using part of the same bus. One LED was short circuited, which disabled one
line shared with the keys, taking out the whole bunch of notes.



Gareth.