I mean Service Extender Boards as in the ones needed to lift a board above
and out of a chassis for electrical testing. The boards in the FT-101 are
inserted into chassis mounted card edge connectors similarly to a modern
computer. So to test the board electrical characteristics and test points
one needs to have physical access enough to employ test probes.

Thanks for pointing this out.

Paul Pinyot

Wow my memory must be severely broken, My recollections of the Yaesu FT101
was that it was a tube radio, although I have no recolection below the
chassis.