Take a look here: @braddr discovered an easier solution: #1 (comment)
Designed for Keithley 2001 (MEM2 option). More infos here: https://xdevs.com/article/kei200x-mem/
Idea from TxB @eevblog forum: https://www.eevblog.com/forum/testgear/tek-csa7404-repair-project/msg1404582/#msg1404582
Now tested and working.
