I’ve been building our nixie tube production facility from scratch since 2011. There is not a single piece of machinery obtained from closed vacuum tube companies. All pieces of nixie tube manufacture technology we have was built in-house, mostly using parts from eBay or second-hand market. On the beginning of development of every manufacturing process, there first must have been deep understanding of the physical/chemical laws on the background. Only with this knowledge, it is possible to make vacuum tubes with consistent quality and long lifespan.

 

Careful cleaning

One of the most important aspects of vacuum tube manufacture is purity of all materials and parts used for assembly of the internal system. Our washing procedure is based on processes used for preparation of material for ultra high vacuum apparatus. Ceramic insulators, mica holders and other difficult to clean parts are washed in ultrasonic baths in appropriate cleaning agents. Parts with simpler surface – metal parts, glass parts, are washed in automated laboratory washer. As a final step, all parts are rinsed by deionised water and dried. Since this moment, they are strictly handled with gloves only.

Washing parts prior to assembly in automatic lab washer.

Assembly of internal electrode system.

Hand assembly

The assembly of internal parts is done completely by hand. The anode grid is first folded, all digits are put inside with ceramic rings as an electrical insulators between adjacent digits. Backplate is placed on the top of the stack and joined to the anode grid by spotwelding. This operation is followed with mounting of mica holders and pinched stem (the part where wires go through glass). Getter is added as a last part before inserting the internal system into a glass envelope.

Glasswork

There are couple of glassworking operations involved in the nixie tube manufacture. All of them are made by hand on a glassblower’s lathe using hand oxygen/propane burners.

Sealing glass stem into envelope.

Induction heating of internal metal parts to drive out residual gases and improve purity of the final tube.

Vacuum pumping and gas filling

Before the filling with gas mixture, the tube must be pumped to high vacuum and gas contaminants included in the internal parts must be driven out. This is done by heating with oven also induction heating. Our pumping-filling machine is built completely in-house, it utilizes turbomolecular pumps and modern vacuum gauges to get batch-to-batch consistent results.

Burn-in

Every tube must go through burn-in process to get

Soldering the lead wires to the tube base.

Final testing – observation.

Testing

Every tube going to customer must be tested prior to shipping. What may be surprising in our technology age, the most important testing process is checking of color of the glow with human eye, comparing it to other glowing tubes. No other parameters (striking voltage, current, etc..) can tell more about the tube health than color of the glow. It takes quite some time to train your eye for recognition of the small differences in color of the glow.