All Jelco tonearms use a standard Linn tonearm mount.
Here is the mounting template for the 12″ SA-750DB tonearm. The mount for the 9″/10″ SA-750, 9″ SA-250, 9″ SA-250ST.
Jelco SA-750LB mounting template
From the drawing one can see that the center hole for the arm tube is 30mm diameter. There are three mounting screws 120degrees apart on a 48.2mm diameter circumference.
Posted in: Jelco Tonearms and Accessories