Datasheet, pinout, or hint for IV-29 single-dot VFD?

[Mark03]

Several years ago I purchased two IN-28 and two IV-29 from a gentleman in Ukraine.  The IN-28s I used in a Nixie clock project, but the IV-29s are still sitting in my tube collection.  If I had any data at the time, I've since lost it, and careful googling doesn't offer any hints.  The IV-29 does not appear in Dieter's data archive.

Clearly someone knows how to light up a IV-29, as there are modern photos of it glowing a pretty turquoise.  Does anyone here know the pinout, or better yet, have an actual datasheet?

Thanks,
Mark

[Tomasz Kowalczyk]

If you have a regulated power supply (ideally a 2-channel lab supply), you can figure out the pinout and operating conditions by looking at the interiors and powering it up. Find the connections of the filament, connect the supply and slowly increase the voltage until you see the wire to start glowing - this will be the maximum operating voltage. I guess that it will be in 1-1,5V range, so start from ~0,5V. After figuring the filament, find the grid and anode connections and apply some higher voltage to both, my wild guess is that a 25V anode voltage should be right for continous operation, and 40-50V with pulsed operation. My guesses are based on other russian VFD tubes from same times, so I think the technology would be similar. If you are afraid of destroying the tube, start with ~5V and raise until the phoshor area is lighted evenly.

Of course, those voltages should be connected to a commong ground level (so one end of filament would be on the same voltage level as negative voltage terminal from high voltage supply).

It seems to have identical dimensions as IN-28.

Also, when looking at IN-28 datasheet, we can see anode, cathode and grid. This is curious, as nixies do not use a grid, just anode and cathodes. This weird 0 symbol on top of IN-28 might be for "dimmed" operation mode or it's there just because in IV-29 that's the filament connection, so my another wild guess is that the same pins are used in IV-29 - filament in place of "anode", grid in place of "grid" and anode in place of "cathode". This would make perfect sense as in nixies it's the cathode thad glows, and in VFD displays it's the anode.

The only thing that cannot be really measured is the maximum anode voltage. Without datasheet the only way is to set the anode voltage, leave it for operation for a month, check if it changed, raise the voltage by 5V and repeat. So the safest way is to use the lowest voltage that provides even lightning.

[Tomasz Kowalczyk]

Good news, I've searched for data by googling iv-29 in russian letters (ив-29). The results are:

It seems that grid is internally connected to anode (makes sense, however it prevents from using it as a triode - yes, some people actually did that and there was someone who build a radio receiver on VFD tubes).

W dniu niedziela, 14 maja 2017 03:20:56 UTC+2 użytkownik Mark03 napisał:

[Mark03]

Thanks Tomasz, I took a closer look at the tube at it's actually quite easy to see which pin goes where.  There are two filament connections, then the rest of the wires are tied together internally.

With the recommended voltages (1.1V filament and 20+ V anode), I get nice cyan glow.  I have to say, though, it's a slight let-down after the extreme brightness of the IN-28 neon :)  Maybe it wants a higher anode voltage; my bench supply only goes to 25V.

I assume it is normal for the filament to be glowing in operation.  The Noritake VFD page suggests there is a saturation characteristic for luminance vs filament voltage; I guess I should be aiming for the 80% or 90% point there.

Mark