I inherited an MFJ-986 differential tuner, and the little copper lock at the back / rear left side of the roller inductor was broken. I just called MFJ to order the part and their tech talked to me and said that the whole parasitic killer assembly with the hexagonal shaft, fiber switching tabs, aluminum shorting tab and back copper lock tab are no longer needed. Engineering has recently decided this doesn't really do anything, and rather than fix it, I was told to just completely remove it. I was told if problems develop, they will send me a complete roller assembly free of charge. Thought I would post this for everyone's info. 73.
Todd - KT0DD