Archive of the former Yahoo!Groups mailing list: Korg Poly800/EX800 Users

No that didnt work, theyre obviously doing something. 
It does zero as its at the middle point between the other two taps, but it also moves from 0-5 depending on wiper movement (theres 5K to both the 0 and 10K point). 
If you look at the schematic (that I wont pretend to understand fully) theres nothing else from the pots connected to the LFO ( +/- 10 on the schematic) than the 4 line. 
So Im thinking the 4th and 8th terminals is used as both a center and as mod amount somehow.