Is that the one with backlit membrane buttons ?
What they may be doing is putting the button commands into a small IC
then sending one line to the micro. Also check the TAC switches for
being closed & locking out all of them. Look for rust, water stains
& damaged membrane.
I did quite a few PVM's but the only problem on most was a 'litic in
the vert.
73 Zeno
LFOD !