Here we go, pulling apart a Japanese Pioneer LaserActive PAC-S1.

The PAC-S1 is the Japanese version of the Sega PAC, with the PAC-S10 being its North American counterpart.

They are closely related, but documented hardware revisions exist, so I would not assume that every internal detail is identical across every PAC-S1 and PAC-S10.

This video documents the particular PAC-S1 unit I actually had on the bench.

Sources