IR filter for old home tube camera question

[ARC Tech-109]

As I understand from my old service notes the glass assembly on the front is an apochromatic lens and has three dedicated elements to compensate for chromatic aberration so the blue didn't bloom or fringe from back focus tracking errors. All the elements together affect the overall focal depth so this is why it won't focus.

This was all outlined in I believe an Ikegami or JVC service manual I stuck my nose in decades ago when the pb tube was still king.