Leitz Ortholux-Pol FS-45 tube Repair?

[Lightsurfer]

 In the past, somewhere I have seen a repair procedure for the FS-45 Pol tube bertrand lens cable repair. I can't remember if it was a written out "step-by-step" with still photos, or a Youtube type video. Can anyone point me to such a production? I have one for the Orthoplan FSA-50, but need to work on my Ortholux-Pol.

Many thanks,
Howard