@penguin42 Honestly have no idea. May have been dwindling parts supplies as they transitioned from EM to solid-state (there are also weird inconsistencies in the machine re: what the devices are called and what is screen-printed on the PCB).
But it could also have been different needs. The bonus unit is wire point-to-point on the other side and thus may be more flexible.

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@TechConnectify behind the scenes question: What is it you do after failed takes in the bloopers? Do you have a button wired up to set an edit point in the recording? Reset a clock?
Great video and series btw!
@TechConnectify "I've summoned a clicky thing for your convienance"
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@TechConnectify The stepper PCBs are almost jarring to see in this thing that looks like it was built from coathanger wire and plywood. I appreciate the amount of work put into it, but I also appreciate its barbarian aesthetic, the bits of handwriting, bare soldering- it makes you imagine the whole factory just looking at it.
They reminded me of gray-code rotary encoders like you'd see on a multimeter's main switch, but it's far too detached in construction and purpose to call it a Technology Connection.
@TechConnectify
Looking forward to Episode 3.
What a wonderfully complex machine.