Sperry SP-425-08 Display - Datasheet?

Brent Hilpert bhilpert at shaw.ca
Wed Jan 1 19:34:02 CST 2020

On 2020-Jan-01, at 2:42 PM, Anders Nelson via cctalk wrote:
> I snagged one of these Nixie-like displays (from a calculator I assume) and
> I'd like to light it up. Does anyone know where I might find the datasheet
> for it? Google hasn't turned up anything.
> https://www.ebay.com/itm/264110638970
> Any help is appreciated!

7-segment multiplexed multi-digit gas-discharge display.

Those Sperry types weren't very prevalent, I'm not surprised you haven't found a datasheet.

I'm being a little presumptuous in specifying gas-disharge, it certainly appears to be, but the ebay pics are a little small.

There was another series of GD displays from Sperry, and another from Beckman, which were more prevalent.

Assuming it is GD:

I have an example of one that appears to be of similar construction to yours in this calculator:
Given yours says made in Japan, I wonder if they be from the same OEM.
I can send the schematic if you wish, for an example of drive circuitry.
It needs a little reformatting and conversion to pdf first, so let me know if interested.

I have other calculators and schematics using the Beckman displays (7-segment, multiplexed, multi-digit, gas-discharge).
They could also be comparitive examples for drive circuitry.

Multiplexed gas discharge displays could be a little finicky to drive, to keep down anomylous ghosting and partial ignition.

In the absence of a datasheet, your first task would be to distinguish the digit anodes from the segment cathodes.
You might be able to do it visually by looking at the internal construction.
Otherwise experimentation with two probes connected to a 150-200V power supply with a series limiting resistor of 200K or maybe even higher to start with.

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