The LAG is labeled "HAL16R8CN 8440 /
342-0251-A" so it does look like a
 custom ("HAL") chip such as what Tony was mentioning.  Guess that would be
 tough to replace, unless someone out there has the means to make a
 dupilicate.  Bah.  That'll teach me to think twice next time I think I
 know what I'm doing :). 
    I remember reading somewhere that a guy from an old repair shop reverse
engineered these equations and put it online. Google is your friend :o)