Johnson JPB-5100 - All or some of the function keys do not respond (JPC;B;S;E)

All or some of the function keys do not respond (JPC/B/S/E)
Possible causes:
1. Keypad connecting
plug has been not fit-
in properly.
2. Keypad is damaged.
3. Upper board is
damaged.
Fix:
1. Remove the console cover, and then check if
keypad cable is connected properly to the upper
board.
u If it has not been connected well, reconnect it
to the terminal and check again.
.
2. Keypad or upper board is damaged.
u Replace the console.
2-3 Revision: 1.0 Date: 2001/06/01