Going up, going down

Raided some stowed away boxes this weekend and found some interesting displays in them. Among them were 2 Otis elevator VFD displays bought long ago on Ebay. Each module has 2 large alphanumeric characters which would make for some nice score displays or something along those lines.

Never got around to figuring out how they work, until today. Tracing lines, searching for datasheets and some guesswork resulted in 2 schematics. You’ll notice the data, load enable, data out and clock going nowhere. These go to an Oki MSM5267B-15 33-bit VFD segment driver. It requires a voltage between 8V and 18V and the rest of the components have an even larger range.

You’ll also notice some unused parts. These are on the PCB, but most likely not needed to get this thing to work, so I cut some corners. Let’s say I’m more a digital man and still trying to interpret some parts (what do those comparators do!?), but it seems these babies will come to life soon.

Otis VFD schematic 1 – Control

Otis VFD schematic 2 – Power

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