A failed experiment: Making the B7971 Nixie tube
dudu sa
When disassembling and studying two different models of the B7971, I found that it made extensive use of mica sheets as the substrate and some pads as connectors to link the cathodes to the pins. This assembly method is extremely cumbersome, so I began to wonder if, in 2025, there might be new solutions for making the backplate material of the B7971.
After a long investigation, I found a very good solution—Rogers high-frequency boards. According to the manufacturer’s description, they use ceramic material, which allows them to withstand high temperatures. In addition, circuits can be printed on the back of the board, eliminating the need to make metal strips for connecting the electrodes. It sounded like a very promising choice.
So I began designing a solution based on Rogers circuit boards to make the B7971, including electrode shapes, routing, and so on.
If successful, this would be a very good option. To verify the solution, I spent a large amount of money on producing Rogers circuit boards. I must say, the prototyping cost was really expensive, but there was no other way for the sake of R&D. To test this ingenious idea, I had to make a bold attempt.
After a long wait, I finally received the package. The moment I got it, I felt extremely uneasy. On one hand, I was very excited about this solution and hoped it would successfully achieve my goal. On the other hand, if it failed, it would mean that all the time and money I had invested would be wasted.
The moment I opened it, I was stunned—what the fuck, why is this board soft? From my experience, pure ceramics, whether alumina or zirconia, are extremely hard materials. How could it possibly bend so easily? Could it be that this isn’t pure ceramic? To verify this thought, I decided to test it with a hot air gun.
Oh no, this was such a huge disappointment—it really wasn’t ceramic. Burn marks actually appeared on the circuit board, and at that moment my mood hit rock bottom as I began to search for the truth behind it.
It turned out that Rogers boards are a composite material—they are doped with ceramics and not pure ceramic. I felt very sad; this perfect solution was just rejected like that.
But even so, I didn’t give up. I wanted to try other materials. My idea was to skip the baking during evacuation—just vacuum the tube and then fill it with gas. Although the impurity content would be high, it would be enough to verify whether my electrodes could function properly.
So, I began assembling the electrode materials. I carefully mounted them onto the substrate and then used solder wire to connect them to the pins.
These are the cathodes used for emitting light made by us, with the pins fixed to the back substrate.
This is what it looks like after assembly.
Next, I connected them to the base.
Everything looked perfect, even if it didn’t seem entirely reasonable. Next, I sealed the base with the lamp envelope.
As it turned out, I was defeated once again. During the sealing process, the high temperature of the flame scorched the Rogers circuit board. It released a large amount of toxic gases, severely contaminating the inner walls of the tube.
As expected, the seal soon cracked. Due to the release of severe contaminants, a large amount of impurities got mixed in while sealing the base and the lamp envelope, causing the entire tube to start splitting during the cooling process.
That was the end—this entire approach ended in complete failure. The reason can be summarized as insufficient preliminary research; I hadn’t fully understood the temperature range of Rogers boards. But even if I had known in advance, I think I would still have tried this approach, because sometimes the listed range only indicates normal usage and doesn’t represent the material’s actual temperature limit.
I’m very sorry to the friends who have been waiting—I know you’ll have to wait a little longer. Developing a new Nixie tube is not easy; this is just one failed case. However, the problem isn’t insurmountable, and I will immediately start working on the next solution.
Finally, I welcome everyone to follow us. We are InixieLab, and I am Sadudu, the founder of the lab. Our website is inixielab.com. We are currently in stable production of 30mm Nixie tubes, the DGM01 and IN-18s. In addition, we are preparing for mass production of the large Z568MAX Nixie tube. We have been testing it for over six months, and so far, the results are very good. We are already preparing the next batch of materials to start small-scale production.
newxito
gregebert
Jeff Walton
Too bad that the 7971 experiment was a bust! I applaud you for trying and you obviously learned some things along the way. I appreciate that you and Dalibor have been very open about the issues when they arrive and show us both the good and the bad. It helps to build confidence that your efforts will eventually be successful.
FYI – My IN-18S tubes from your lab are continuing to work well after a few months of use and I am very encouraged about how they have worked so far!
From: neoni...@googlegroups.com <neoni...@googlegroups.com> On Behalf Of dudu sa
Sent: Saturday, September 27, 2025 11:02 AM
To: neonixie-l <neoni...@googlegroups.com>
Subject: [neonixie-l] A failed experiment: Making the B7971 Nixie tube
About half a year ago, a few friends came to me and asked if I could make a Nixie tube similar to the B7971. As one of the few Nixie tube manufacturers, I thought about it for a while and decided to give it a try.
I am very grateful to Adam for sending me a B7971 sample—thanks to his sample, I was able to accurately measure the filament length, dimensions, and other parameters.
When disassembling and studying two different models of the B7971, I found that it made extensive use of mica sheets as the substrate and some pads as connectors to link the cathodes to the pins. This assembly method is extremely cumbersome, so I began to wonder if, in 2025, there might be new solutions for making the backplate material of the B7971.
After a long investigation, I found a very good solution—Rogers high-frequency boards. According to the manufacturer’s description, they use ceramic material, which allows them to withstand high temperatures. In addition, circuits can be printed on the back of the board, eliminating the need to make metal strips for connecting the electrodes. It sounded like a very promising choice.
So I began designing a solution based on Rogers circuit boards to make the B7971, including electrode shapes, routing, and so on.
If successful, this would be a very good option. To verify the solution, I spent a large amount of money on producing Rogers circuit boards. I must say, the prototyping cost was really expensive, but there was no other way for the sake of R&D. To test this ingenious idea, I had to make a bold attempt.
After a long wait, I finally received the package. The moment I got it, I felt extremely uneasy. On one hand, I was very excited about this solution and hoped it would successfully achieve my goal. On the other hand, if it failed, it would mean that all the time and money I had invested would be wasted.
The moment I opened it, I was stunned—what the fuck, why is this board soft? From my experience, pure ceramics, whether alumina or zirconia, are extremely hard materials. How could it possibly bend so easily? Could it be that this isn’t pure ceramic? To verify this thought, I decided to test it with a hot air gun.
Oh no, this was such a huge disappointment—it really wasn’t ceramic. Burn marks actually appeared on the circuit board, and at that moment my mood hit rock bottom as I began to search for the truth behind it.
It turned out that Rogers boards are a composite material—they are doped with ceramics and not pure ceramic. I felt very sad; this perfect solution was just rejected like that.
But even so, I didn’t give up. I wanted to try other materials. My idea was to skip the baking during evacuation—just vacuum the tube and then fill it with gas. Although the impurity content would be high, it would be enough to verify whether my electrodes could function properly.
So, I began assembling the electrode materials. I carefully mounted them onto the substrate and then used solder wire to connect them to the pins.
These are the cathodes used for emitting light made by us, with the pins fixed to the back substrate.
This is what it looks like after assembly.
Next, I connected them to the base.
Everything looked perfect, even if it didn’t seem entirely reasonable. Next, I sealed the base with the lamp envelope.
As it turned out, I was defeated once again. During the sealing process, the high temperature of the flame scorched the Rogers circuit board. It released a large amount of toxic gases, severely contaminating the inner walls of the tube.
As expected, the seal soon cracked. Due to the release of severe contaminants, a large amount of impurities got mixed in while sealing the base and the lamp envelope, causing the entire tube to start splitting during the cooling process.
That was the end—this entire approach ended in complete failure. The reason can be summarized as insufficient preliminary research; I hadn’t fully understood the temperature range of Rogers boards. But even if I had known in advance, I think I would still have tried this approach, because sometimes the listed range only indicates normal usage and doesn’t represent the material’s actual temperature limit.
I’m very sorry to the friends who have been waiting—I know you’ll have to wait a little longer. Developing a new Nixie tube is not easy; this is just one failed case. However, the problem isn’t insurmountable, and I will immediately start working on the next solution.
Finally, I welcome everyone to follow us. We are InixieLab, and I am Sadudu, the founder of the lab. Our website is inixielab.com. We are currently in stable production of 30mm Nixie tubes, the DGM01 and IN-18s. In addition, we are preparing for mass production of the large Z568MAX Nixie tube. We have been testing it for over six months, and so far, the results are very good. We are already preparing the next batch of materials to start small-scale production.
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guus.a...@wolmail.nl
Guus Assmann.
If it works well, I would like some large Nixies as a "thank you".... :-)
Op 27-09-2025 18:01 CEST schreef dudu sa <sadu...@gmail.com>:
--
Mac Doktor
On Sep 27, 2025, at 12:01 PM, dudu sa <sadu...@gmail.com> wrote:About half a year ago, a few friends came to me and asked if I could make a Nixie tube similar to the B7971. As one of the few Nixie tube manufacturers, I thought about it for a while and decided to give it a try.
On Sep 27, 2025, at 10:28 PM, metasonix wrote:
Well....I could have told him (for free) this wouldn't work. Only materials that can be heated and outgassed FULLY can be put inside a high-vacuum or gas tube.
This is apparently the stuff he tried to use. It has great dielectric characteristics, but there is nothing about using it in a vacuum.
https://rogerscorp.com/advanced-electronics-solutions/ro4000-series-laminates
Maybe talk to a company that makes thin film hybrid circuits. They can probably make a degassable board out of alumina with traces that can be spot-welded, since they have been making such things for 60+ years. It will NOT be a bargain. Feel free to repost this to the group.
https://www.thinfilm.com/substrates.html
https://www.coorstek.com/en/industries/electronics/microelectronics/thin-film-electronic-substrates/
All modern electronic components are made with some kind of plastics, epoxies, or phenolics or whatever. None of which can be processed in a tube. Even Teflon will eventually disintegrate into hydrogen fluoride and other things.
If they manage to build a working B7971, they are well within their rights to charge a very stiff price, at least $500 retail and probably more. Making such things in the 1950s was easier because mica was cheaper, one could buy parts and envelopes from third parties, and you could pay bored housewives 50c/hour to assemble the damn things.
That price may seem slightly high but Eric knows all about actually recouping an investment and earning a living. As well as dealing with customers who can't figure out how to use his products.
"The Mac Doctor"
Rik Declercq
Hello Sadudu,Sorry that it failed and thanks for sharing.
And this cup is made of.... Ceramics.So why not make the PCB / shape plate out of clay and bake that.Once baked, the clay can withstand quite high temperatures.And it will not deform once it is backed.Also, a test with this needs not be very expensive.Most likely there are quite a few "hobby-potorists" to be found to use an oven.Just a thought to ponder on... :-)
Leroy Jones
Neil QQ
J Forbes
