Posted on July 24, 2012
Unidisk 3.5, or the strange case of the elusive gear
Apparently my passion for retro computers have become an obssesion. The problem is that the Apple II model in particular had a very attractive design, and peripherals for this were also very asthetic pleasing. There was a line dedicated specifically to the Apple //c, consisting of CPU, three monitors (color 14″, Green 9″, LCD flat panel 11 “), mouse, joystick, external Drive 5.25, UniDisk 3.5, and AppleScribe printer. All shared the same cream-colored parallel lines, inclined buttons and curved lines.
Of these peripherals, over time some have become rare pieces that are hard to get: the most expensive of all is the LCD, which have been sold around $ 400 dollars, followed by the color monitor (ColorMonitor IIc) and external disk UniDisk 3.5, which sell for $ 100-200 depending on their condition.
The Undisk 3.5 is a floppy unit for 3.5 inch disks, cream color, but by itself is very special: it is a smart drive, as it contains an 65C02 CPU, memory and firmware on board. it sets the interleave to 4:1. to handle the slow data transfer rate between the drive/card and the //c’s system bus.
For this reason UniDisk readers are difficult to obtain. I was lucky enough to get one through a site dedicated to these systems, where a user it sold an extra good price, $ 35.
A few days later, the person who had sold me the monitor contact me offering me the same unit, but broken. Just bought it and start to repair it. It turns out that these drives have an automatic loading and unloading system for the floppy, make use of an internal motor with gear sensitive plastic, which does break. There is even a video showing this.
Exactly this was the problem: an engagement was broken in half and getting a replacement was a complete ordeal. Online course is very difficult to get a specific gear. I searched hobby stores, where they have parts for remote controlled models use small gear as I need. I managed to get one almost the same, but was an inch bigger and does not allow rotation.
I have several options for fixing the engine:
buy a used unit and remove the gear
keep looking at scale models stores
buy bags of gear hoping to find the right size
make a new one in a 3D printer
This last option I like, by the novelty and fun they mean. I have found in my city a “Maker Shop” is a kind of warehouse where they have tools and 3D printers, cutters, etc. for people to go and work on your electronic projects and prototypes.
For now I was lucky to find a pair of discs for Mac for $ 20, I bought and replaced the mechanism so that I have both drives working. I will put on sale one of the UniDisk to recover my investment, and soon go to “Shop Maker” to create the elusive gear and fun as only a “geek” knows how.