Not just an replacement, but an improvement!

Factory Tour...

This page was uploaded: 15-dez-13

Welcome to our factory touractory Tour...

Please don't expect to see heavy industry here. We make everything by hand. Tony (top right on the picture) started as a one man company, not very long ago. Now we have several employees, and we just moved into a new building. On the top left of the picture is Jarda, our main technician.

We are a small and highly motivated production team. All of us used to work in the larger tube facilities in and around Prague, and is a specialist on his own area. Now we have combinded our skills, and we want to show what we are capable of, building these quality products. We have a close to 100% production depth, and build everything the traditional way. This means: all that goes into the factory is glass pipes, mica, ceramic and metal. (Not to forget many different chemicals) Some of this production depth is wanted, so we are less independing of supplier companies that not allways do as we need or as we want. On the other hand it is also necesary because buying products for tube production is getting harder every year. So today we thick metal wire from one company, send it for refinement to another company, and from this we make a product we need. However 20 years ago you could buy this product from several catalogs, from a normal vacuum supplies company. These days are gone. From some of the very rare parts, like very thin nickel pipes of special alloy, we have a lifetime supply.


Part I. Assembly of the tube.

This is what we need to prepare for assembling one tube:

1x glass inside socket, 1x glass bulb with EML logo on it, 8x filaments, 8x filament springs,1x grid, 2x Plates, 4x Plate coolers,2x Grid coolers, 4x bars to connect the plates to, 1x socket, with part number on it, 4x socket pins, 2x mica plates, 4x spacers for the tube top, 2x holders for the getter, 2x getter rings, 1x Set of connection wires + connectors on the bottem mica. (12 pieces), 1x Metal tag with individual number (inside)

We won't bore you with the complete list, but it is about 140...160 pieces, depending on the tube type.


Here you see Tony operating a small machine, that is hand made, to blow the tube inner glass base. The gas flame you see in the middle of the picture.

This is the result from the above picture. Many steps have to be done before this is ready.

1) Here the tube inner system will connected by electric welding
2) Copper wires that are soldered into the base
3) Thin glass pipe, used to vacuum the tube later.

This is a chemical treatment of the tueb base glass, that will later reduce the grid current of the tube. It needs to be done under infra red light to prevent any moisture.
This is a new made grid winder machine. It is dedicated to the EML grid construction.
This is simple but good working equipment, used to stamp the plates. The pressure comes from the swing energy in the weights (yellow colored) The operator swings the weights fast, and the plate stamps are slowly moving down from that. The machine gets suddenly stopped by the plates. It says "bang", swings back, and then the plates are stamped.
This is Jarda, preparing filaments. The wires are covered with emission liquid. This is ultra clean work. The smallest dirt particle in the tube can already caus that this tube isn't going to work very good. To keep all materials clean, we store every piece part in vacuumed glass jars for as long as we need. Still, it is better to make tubes from those parts quickly, and close the bulb the sooner the better. This requires a lot of discipline, and good planning of the process. The result will be a reliable tube.
Final assembly of the 1605 tube, inner system. In the open condition, the tube may be on the air for maximum four hours. Reason is the contamibation by air humidity.
These systems are ready for the glass envelopenow
Now we can't just take some glass bulbs from stock. We need to hand make them, on a self constructed machine. The glass pipe is rotating, and at the end clamped into the "negative" which is a carbon shape. You can not see this, because it is covered by the flame.

Tube glass must is a very pure glass, and it has nothing to do with the glass you see glass blowers use, to make a wine glass, or something like that. Tube glass needs a lot of tempering while heating and cooling it. If you don't do that, you will have cracks in the glass. It takes a good glass blower to make reliable bulbs, this is pure craftsmanship.

Well, this one looks nice! It can be cut off the pipe. Some carbon residue needs to be cleaned off when it's cold.
Ok! Finished. This took two hours.
At the end at all of all this, we have the tubes ready, that will be pumped vacuum the next day. Until then, we store them in vacuum. to keep contamination away from the tube inside. What you see here is a vacuum room.
This is Renata, making ceramic bases. She takes the parts out of the oven to let them cool down.

What comes in to the factory is really only glass, metal and raw materials. We make every piecepart of the tubes ourselves. This is the oven to burn-in the gold primting on the base.

Here you see the inspecting of the bases before assembling the pins. Most of the time they need some fine rework so the pins fit the holes nice and exactly.


Part II. Activation of the tube.


First the tube is pumped at vacuum, while the somplete inner system is heated up red-glowing, by microwave heating. We use a 3kilioWatt microwave tube for this. The energy is leaded out of the generator, via a spiral shaped antenna, which radiates the energy into the tubes. (look at the antenna in one of the next pictures) This is Jarda's work and specialty.
This is a detail from the left picture, where you see the tube tipped off the vacuum pump. The smallest mistake, and the tube is damaged. If air gets in, the tube needs to be refilamented, which is close to building a new tube.
This is an induction heater, to outglow the getters. Interesting is the water cooling of the coil.

Part III. Performing tests.


So now, the tubes are ready. Making tubes is one thing, testing them anoter. Some part of the testing is the observation how the tube gets to life, while it is vacuum pumped. (must be done on a working tube...!) We have test equipment that we partially build ourself, and partially bought from some closing tube factories.
This is a normal burn-in bench l for vacuum tubes. As a plate resistor, light bulbs are used. The bulb act as a fuse, and as current limiter. We can burn in 10 tubes at a time. During burn in, we can monitor six essential parameters of each tube.
This is Jarda, doing the parametrical test on the tubes. This particular set up will measure the grid current at full power. Apart from the burn-in table, we test only one tube at a time. We save all data in an Excel file, of each tube we make.
What you see here is the hot air soldering of the tube pins. Jarda is very good at it.

In this corner of his office, Tony does the listening test of the tubes. It is a good feeling to hear them come alive. A bit loud sometimes...

There is nothing the master's eye will not see ;)


Dear Customer, this is how we make our tubes. I think you have an idea now for what it takes to build these by hand, the all traditional way, like it was done 50 years ago already.

We hope you understand now, why we can not build these tubes for the same prices as automated factories can, but the result is worth it!

With your support, we'll be able to continue this wonderfull work.

We hope you enjoyed this tour!

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