Nixie Tube or Neon Lamp? - Exclamation mark vacuum tube

[ScottBouch]

Hi all,

Can someone please provide some guidance on this vacuum tube?

1 - Is it a Nixie Tube or Neon Lamp?
2 - How do I test it and then illuminate it?

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Does anyone recognise this tube, or have any information on connections / voltages, etc..? unfortunately there are no markings or numbers on the tube itself. I have a socket that came with it, with wires connected, but I'm not to know if these wires are connected to the right pins or not.

It's something I just came by some years ago, so I have no information on it, or knowledge on it's condition. But I'd love to fire it up.

I have a Labpack PSU which can deliver up to 300Vdc HT. And LT side up to 25Vdc or ac variable. Also offers fixed 120Vac, and 6.3Vac.



I'm just learning about Valve technology, so please forgive me if I have any basic questions.

I know they say "a little knowledge is dangerous", but I'm wise enough to know to do my research first before going straight ahead and blowing it up / electrocuting myself!

Cheers, Scott.

[paulsherwin]

Looks like a DM70 tuning indicator: http://www.r-type.org/exhib/aaa0705.htm

[TonyDuell]

It looks a lot like a DM71 to me. This is a hot cathode vacuum device (not a neon lamp or nixie tube), and was used as a tuning indicator, tape recorder level indicator, etc.

There is some data available here :

http://www.r-type.org/exhib/abc0007.htm

[Nickthedentist]

Originally Posted by TonyDuell

This is a hot cathode vacuum device

...a special type of "valve" in other words.

[ScottBouch]

Fantastic help, thank you guys!

Both web pages you've shared have the datasheets for the DM70 or DM71, so I can hopefully diagnose from the sheets which type it is... Then think carefully about a circuit to activate it.

It does a lot more than I'd anticipated, it's quite a clever device!

Thanks, Scott.

[ScottBouch]

Great video here: http://www.decadecounter.com/vta/art....php?item=1067

Ooooh.. now I can't wait to get it working!!

Wonder what circuit this guy is using to control the -ve voltage relative to the music?

Cheers, Scott.

[paulsherwin]

The DM70 and 71 are identical apart from the 70 having wires to be soldered and the 71 having pins for a socket.

[ScottBouch]

Oh excellent, thank you - I was finding the datasheets to have similar characteristics!

This would be a 71 then.

Been reading the datasheets, would I be correct to assume that the "Plate" is the "Anode" (Pin 8)?

Reckon I could have this fired up tonight!

Thanks, Scott.

[paulsherwin]

Plate is Americanese for anode, so you will see it on American datasheets. You will also see references to B+ (HT).

Take care not to exceed 1.5V on the filament, as these are quite fragile

[ScottBouch]

Thanks for the explanation! Yes, the datasheets do say about 1.4V for the heater..



Would this be an adequate test circuit? Is it ok to use AC for the heater and DC for the Grid and Anode?

Thanks, Scott

[Andrew B]

I would use a 1.5 volt "dry" battery for the filament, better safe than sorry.

[ScottBouch]

Excellent tip, thank you!

Your Tux is noted, from a fellow Linux fan!

[Andrew B]

Been running it for 15 years, that "other" system drove me nuts breaking down all the time, all the nag screens etc........

[paulsherwin]

Please stay on topic.

Valves designed for battery operation have filaments which act as both the heating element and the cathode. Mains valves normally have separate cathodes and heating elements and are intended for AC operation. In the specific case of a DM71 an AC filament supply would probably work without ill effects, but I've never tried it. As Andrew says, a 1.5V battery is the best solution, especially if you select one where the voltage has dropped a bit.

[ScottBouch]

Thank you, I'll do that, and not stray form topic..

So do you think the following circuit is reasonable?



I've shown the cell as 1.4V as you recommended to find one a bit discharged..

Thanks, Scott.

[G6Tanuki]

AC is OK on the heaters of a DM71: Eddystone used an AC-heatered DM71 in their 840C receiver, where the DM71 was the "nearest-to-chassis-voltage" valve in a series-connected AC/DC heater string.

Well worth getting it going, my plastic EKCO valve VHF only radio has one, it looks lovely.

[ScottBouch]

Well, last night I got as far as checking the cathode heater / filament resistance - 15 ohms, so happy it's not burnt out!

Then I got into a deep conversation with the next door neighbour so progress stopped!

Hoping to power it up tonight now...

Cheers, Scott

[Maarten]

In terms of modern displays, the DM70 is quite closely related to the VFD. Some would say it actually is a VFD, but then again a DM160 is even closer to a modern VFD.

[Heatercathodeshort]

Don't get too excited. Probably the least interesting tuning indicator of all time! John.