Having just dismantled my ImageWriter II prior to throwing it out, I can
explain parts of the assembly in great detail.
The entire print head assembly is connected to the rest of the printer
via a flexible cable, but the print head assembly is a rather large and
complex beast which also has a mounting place for the ribbon cartridge,
vertical position adjustment (for aligning the colour ribbon), motor for
driving the ribbon, etc.
The print head itself is conected to the head assembly with a small slot
into which the print head is directly inserted.