OT: Nixie Tubes

Thanks!

Enjoy, DoN.

They are just special neon lamps. They take something over a hundred volts to fire (light) and then the voltage drops back to around 90 volts.

One precaution. They will draw as much current as they can - to the point of destruction. Apply the voltage through a resistor to limit the current. Something like 47K to 100K and a 130ish volts ought to do as a first experiment.

You will find one of the pins is the common anode which goes to the positive of the supply. There is a separate pin for each of the digits which goes to the negative of the supply. Usually you can dope out the connections by close observation of where the leads go inside the tube.

There used to be ICs made just to drive these things. You can probably turn up data sheets and probably parts with a little Googling.

-- W§ mostly in m.s -

That hyperlink shows what we (I used to do it with my Dad as a teen) had to go through in laying out massive designs. Lots of work - but that is a hobby, not work.

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Rick wrote:

I don't have a datasheet handy for the original 7441A, but the 2nd generation 74141 has outputs leakage rated at 55VDC. It blanks for invalid codes for leading-zero blanking etc.

Yes, they're mature cheap multiple-sourced 300V NPN transistors. About a dime new (Fairchild brand) if you buy a whopping $8 worth.

Whether you want to use 7441s or transistors plus, say, CMOS 4017's really depends on your design aims. The ancient TTL parts draw quite a bit of supply current.

Best regards, Spehro Pefhany

Indirect heated cathodes. One of the transformers is only for heaters, the other supplies two anode voltages, screen bias voltage and another set of heaters.

Mark Rand RTFM

No, they just don't bother to draw them. And, he's NOT a "purist" -he succumbed to using silicon diodes in most of the decode circuitry. Yuck. He could have EASILY gone over 100, maybe even 200 tubes if he'd just used vacumm diodes for all the gates! Of course, then it would have caused the clock on his mantel to drive the mantel into the basement!

Power? Good thing they have 230 V over there, as he might have had trouble running this thing on a 120 V 15A circuit in the US. I seem to recall a Tek 555 scope had ~50 tubes in it, and drew 14.9 A from the wall socket. This clock has about 80, I think!

I once worked on a Bendix G-15 computer that had ~300 tubes and 3000+ germanium (I think) diodes in it. What a monstrosity!

Jon

Not to mention that a lot of the original TTL chips have been discontinued, and you may be buying a 20 year old part.

A lot of early TTL chips had crappy plating on the pins, and corroded while in storage, or in some types of sockets. I've had to wire brush and re-tin thousands of them with acid flux, when I had a decent solder pot. Brush, flux, dip, clean, repeat. Whole days of cleaning up bad pins, and replacing cheap sockets.

While the 74xx devices are getting rare, there are a lof of other variations of the device number are commonly available. Try the 74HCT (TTL output levels) or 74HC (CMOS output levels) instead. The TTL devices have a bunch of different variations as shown by the letters after the 74 reference number and you mix and match them as long as you take into consideration the drive requirements input and output of each family of the devices. Anybody still sticking to the original design is missing out on the higher speeds and lower current draws of many of the newer variations available.

-- Yeppie, Bush is such an idiot that He usually outwits everybody else. How dumb!

They are just special neon lamps. They take something over a hundred volts to fire (light) and then the voltage drops back to around 90 volts.

One precaution. They will draw as much current as they can - to the point of destruction. Apply the voltage through a resistor to limit the current. Something like 47K to 100K and a 130ish volts ought to do as a first experiment.

You will find one of the pins is the common anode which goes to the positive of the supply. There is a separate pin for each of the digits which goes to the negative of the supply. Usually you can dope out the connections by close observation of where the leads go inside the tube.

There used to be ICs made just to drive these things. You can probably turn up data sheets and probably parts with a little Googling.

-- W§ mostly in m.s -

A young fellow I know is in an engineering program at the local college. He was assigned to design and build a nixie tube clock as a course project. He seemed not to have any great problem finding any of the parts he needed.

Jerry

I wouldn't have any problem, either. Other than cleaning my shop enough to dig out all the parts, first.

If the project was intended to simulate a real design (for production) process, I hope the prof docked marks if he designed in any obsolete or obsolescent parts, no matter how nicely they seemed to fit the job. It's really a major problem in many segments of the electronics industry.

Best regards, Spehro Pefhany

How many "peanut" tubes do you have? I have four of them, one in a tuner, two in audio amplifiers, and one spare. Gerry :-)} London, Canada

According to Gerald Miller :

Do you mean the "acorn" tubes? I know that I have one in a plastic drawer, and I think that I have some more in an emergency transceiver.

There are also the "pencil" tubes, with the flat pinched bases with in-line pins. I've got a few around somewhere, plus about six or seven in the GR 1551-c Sound Level Meter.

Plus one rather interesting tube, all ceramic and metal, with "pins" being flat extensions of the seals between ceramic rings. From counting the pins, it must be a triode, and rather high frequency as well. Total diameter (exclusive of the "pins") is about 3/8", IIRC.

Plus at least one "lighthouse" triode.

As for Nixies -- most are in old test equipment.

Enjoy, DoN.

According to Spehro Pefhany :

Given that Nixies were a part of the product specification, obsolete (or obsolescent) parts were already part of the given project

-- the Nixies themselves.

Enjoy, DoN.

No, these are about 5/8" dia. by 2 1/2" high with a Bakelite base like the metal base on a dual filament auto bulb but only one locking pin, four contacts on the base similar to the auto bulb. IIRC the filament voltage is 1.1V but each tube had a rheostat and a peek hole to visually adjust the voltage to give a red glow to the filament strand. I don't recall the "B" & "C" voltages offhand but I think they are specified on the amplifier units which were commercially produced while the tuner was home built, or maybe other way about, I haven't had these down off the shelf for a number of years. Each unit is housed in a wooden box with binding posts to link them together. I have many other odd ball tubes including a Westinghouse WD12 which is very similar to the peanut tube but about twice the dimensions, and some of the (pencil ?) tubes from early hearing aides. Gerry :-)} London, Canada

I have a couple dozen different nixie tubes in a half dozen older HP frequency counters that I want to restore.

lists five of them, plus there are one or two more that I can't reach right now. Most of the contents of my electronics shop is still covered in layers of 4 mil plastic from the last several years of hurricanes.

I do have some 1AD4 flat subminiature tubes.

Good point, but of course that part was beyond the designer's control. ;-)

Best regards, Spehro Pefhany