My 1197 lost both DI and SI functionality one day on the lake recently.   It still had 2D and gps/mapping functionality though.  I swapped out the 1197 with my 1198 to verify that it wasn't the transducer.   Humminbird has a $487.50 flat rate for repairs, but I can't see the value of putting that money into a really old unit.   
Is there anything I can check by opening up the unit to possibly remedy the situation?  Is it possible that connections could be loose?   I have had this unit since Feb of 09.