VFD for Olivetti Logos 75s. Question

[isanchez]

Hi,
I have a very nice Olivetti Logos 75s, but the blue VFD is broken...I am trying to find a suitable spare part without success. The problem is that it has 14 digits (all "eight segments" per digit, without "M""+-"), which is not common at all, and it is not implemented in other olivetti models...as far as I know.
As possible solution I have found in ebay 16 digit VFD offered from Russia, but I don't know if it would work. The idea is to connect 14 digits, but I don't know if this is feasible. I don't know how this is connected: by digits, by segments? Would it be compatible?

Maybe you can give me a clue about it. It is absolutely new for me.

Thanks for your help!

Kind regards

Ignacio

[Mark]

Hello Ignacio,
Finding another VFD and trying to fit it to your machine really is, I think, the hard way. First you'll have to get one with at least, approximately the same dimensions. Next you'll need to find out the connections order (pinout) of both displays. The pinouts surely won't match and you'll have some wiring twists to do -provided the needed voltages are the same, which I'm not sure about. Moreover, it may not work if it requires more power than the original, which may result in destroying your machine's processor.

Speaking about pinouts, and to answer your question : these displays are digit-multiplexed, which means that they have 8 segment (grid) connections, one anode connection for each digit and one more for the indicators, not to mention the filament connections. Digits are activated one after another at a rate high enough for the eye not noticing it. They work exactly the way triode vacuum tubes do.

Please have a look at https://en.wikipedia.org/wiki/Vacuum_flu...nt_display for more information.

My feeling is that adapting another display is technically feasible, but with -many?- difficulties. By far the best way would be to find a "donor" machine with an intact VFD.

Maybe some fellow on this forum will have some more suggestions ? (and why not a donor machine ...)
Regards,
Marc

[isanchez]

Hi Mark,

thanks for your clear explanation...I was affraid that there was no feasible solution except to find an old 75S for parts...I appreciate very much your answer.

Kind regards


Ignacio

[Mark]

You're welcome, Ignacio :-)
I wish you good luck !
Marc