Ball size: 2 1/4" (57.25mm)
Slightly updated version of very first trackball marketed by Kensington - TurboMouse #62350 (rebadged Assimilation Process AP07045 Mac Turbo Touch). Physically identical, but with updated PCB modified due to Apple's transition from quadrature to ADB interface. Existing board was used as much as possible: even 8-pin cable connector was still present, while just 4 pins required for ADB actually wired. Mounting places for components required for quadrature output and input are left unpopulated, of course.
The case was also slightly updated: panel-mounted DB-9 connector for daisy-chained mouse removed, and PCB-mounted variant of DIN-4 added on different place - probably, to reduce the manufacturing & assembling cost.
Mechanics of original Assimilation trackball was left 100%-intact. Unfortunately, ball bearings used, Japanese 7R4A made by KYK, are not stainless. Subsequently, they developed severe damage of surface due to corrosion:
Regardless, ball movement is still good. Rubber mounting washers are still elastic after 3 decades. Shutter discs have 15 holes. Contact rollers made of soft polyurethane-like plastic provide good contact with ball surface: no skipping observed. Calculated resolution is 109 PPR / : 15 CPI.
Microcontroller used is Microchip PIC1654-558. Firmware contains ballistic logic with quite steep acceleration curve - but with some practice, it's totally usable. Square switches (rated for 3 million clicks) now suffer from contact bouncing caused by wear and produce unintended double clicks, but still working. Logically, the #62350 and #62352 are single-button devices: both buttons generate Left Mouse Button signal: the right one just duplicates the left button for southpaws.
Old advertising papers from 1987-1988:
I'm planning to convert it to USB interface, and replace worn ball bearings & switches. Despite old-school look, it's very convenient to use, even on modern systems. Low hardware resolution is compensated by internal acceleration, providing adequate pointer control. Traditionally, this trackball was used to prepare this article.
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