Integrated circuits SGS "H 258 B1" and "H 257 B1"

One of the Nixie boards I bought in FN Ham Messe 2022 does not use the usual 7441 Nixie driver + 74xX Latch combo, but rather some undocumented SGS "H 258 B1" and "H 257 B1".

The pinout of H-258-B1 BCD(?)-to-Nixie driver is different from similar documented components (see http://madrona.ca/e/nixieref/index.html for a comprehensive description), so it is worth reversing it from this simple PCB.

I shot a picture of both sides of the board and created a single Xray-like view using an image manipulation software (The GIMP) as I've done in the past. This is the result and a zoomed view of one pair of these ICs:

Both sides of the board with SGS chips.

SGS H257 and H258 combo.

The resulting pinout for H 258 B1 is:

1   input

2   input

3   input

4   digit 2

5   digit 3

6   digit 7

7   digit 6

8   GND

9   digit 4

10  digit 5

11  digit 1

12  digit 0

13  digit 8

14  digit 9

15  input

16  +V

I have no idea and no interest to discover which technology SGS used in 1974 for these parts. I will not use them in any of my projects because I would have no spares or direct replacements.

If you land here looking for a replacement, then contact me.