A warning from my adventures with aftermarket PS one optical-drive assemblies.
Of roughly eight replacement assemblies I bought, only about two arrived with the disc hub sitting high enough to hold and spin the disc properly without further attention.
In 2013 I described that as the motor spindle being “too short”.
A better description is:
the spindle hub was sitting too low on many of the replacement assemblies I received.
The hub is friction-fitted to the motor shaft, so hub position can affect disc clearance and focus range.
I do not have enough surviving measurements to establish whether the motor shafts themselves differed in length.
So this should remain a firsthand warning about my batch of aftermarket assemblies rather than a claim that most replacement PS one lasers everywhere suffer from an inherently short motor spindle.