The AM Forum

Hello All,
           Please find the URL: http://www.youtube.com/watch?v=8_eLO0exato

           It was done by a group of enthusiasts in the Netherlands to celebrate the 100th anniversary of the first triode made by Lee De Forest in 1906. They use a modern technique and machinery, but the result is still the same, a replica of the first triode.

Kewlstuff!

Regards,
           Joe Cro N3IBX

Hey Joe. Check out the fridge behind the guy in the chair.  JOE

YUP that looks like an old time fridge. A replica? OR is that the latest in the Netherlands? Nice video
Fred

Just downloaded us patent 841387, google patents ;)  If a crackhaid can melt up a lightbulb to make "functional glassware," I'm betting I can build a triode in my garage... There was that guy who was making something similar, and made a few tiny CRT's , I have a link to that somewhere too!

I have been thinking about all of the gassy 250TH's, 304's and other other wise OK triodes we have all been sitting on--I bet they can be saved. I work with several outfits that weld glass and quartz so I should be able to learn that art--now all I need is a vacuum pump--any ideas on this????
Skip

Good stuff! Those guy's make it look so easy!
As for rebuilding old tubes I've heard of companies that rebuild the larger power tubes like 833, 4-x series, 3-500, stuff like that, I don't see why it would be limited to them with the proper tools..

For a vacuum pump try eBay.. Look for an A/C Evacuation pump.. They draw a pretty good vacuum.

for a really hard vacuum, you need a system two pumps and a couple valves.
A mechanical backing pump and a Diffusion pump should work. Should pull a really hard vacuum.
if you apply some heat you'll get more out...

The low gain of early tubes like this was the reason that Edwin Armstrong developed regenerative amplification.

The activation of oxide coatings is interesting.  I guess Phillips gave them an unused fluorescent light filament with a barium strontium calcium oxide emissive coating.  I never thought about whether fluorescent light filaments are usually emission-coated, but come to think of it, I guess they would be.

It is interesting that they can actually measure the slight increase in pressure from initial outgassing in the tube.

Love the little resistance welder

What an interesting and well-done film! Well timed to the centennial of the invention of the triode of this month!

This particular group that manufactured the facsimile of the De Forest triode and filmed this process, is a leading edge bunch of guys in Europe that design and build very low power (<10 watts) high-fidelity directly-heated triode audio power amplifiers and preamplifiers. They are the audio analogy of our AM group, in that they design and build virtually all of their own audio gear, and are inveterate experimenters.They do not subscribe to the audiophool mentality; all of their designs are and must be grounded in solid engineering logic and there is no snake oil permitted. I had the pleasure of meeting several of them a number of years ago, and they are a very enthusiastic and highly technical group, a number of whom are active and avid hams. They hale from the Netherlands, Germany, France, Italy, the U.K, Switzerland, Norway, Sweden, etc.

I wonder how many of us are really aware of how incredibly labor intensive vacuum tube production was. It never became a highly automated or rapid process, several toxic materials were used in their manufacture, the process of building tubes was akin to assembling a ship in a bottle, and the level of manufacturing precision required was on par with building a fine watch. Relatively speaking, for the amount of labor involved and the material cost, their selling price was extremely low, especially for high-volume production receiving tubes.  It is amazing that during the Second World War, (and this was one of the largest peaks of tube production), production of all kinds of vacuum tubes was able to keep pace with the inexhaustable demand necessated by the enormous ramp-up of military electronic equipment production, and the requisite spare tubes requirements.

Since Philips in Eindhoven, the Netherlands, was the facility where the assembly of this triode was filmed, it is fitting to bear in mind that the pentode tube was developed by Philips in the late 1920s.

73,

Bruce

I wonder what the amplification factor (u) and transconductance were of the original De Forest triode? The u was probably very low, like many triodes, somewhere on the order of 2 to 8, by my guess, indicating a very low amplification factor. And I'd like to see the characteristic curves of the De Forest device, to see how linear it was. I'm sure this data was taken at some time on the tube.

Yes, I do have a life, but I'm curious!!!!

73,

Bruce

It  makes me wonder what they are going to do with these homebrew tubes?  (There is a box full of them on the table)  It would be interesting to know what the homebrew tube(s) ratings are and if they are being used .  Very cool!

WA1QHQ and myself watched it at lunch time - cool.

GFZ had a pump that could turn your 50C5 into an 813 but that is another story..

WU2D Mike

Skip,
      Howabout the compressor/pump out of an old refrigerator as a vacuum pump for roll your own toobs?

      One caveat: You MUST use annealed glass or else they'll shatter from the heat created by them!

      Best Regards,
                        Joe Cro N3IBX

Joe - Those old "birdcage" Frigidare and GE's, etc. give me major wood. I'd love to own one!

BTW, There was a 1965 edition of QST that had a kewl article about a guy in Argentina that rolled his own vacuum tubes. When I get a chance I'll try to find the issue and article. Apparently he was fairly successful, since he made his own triode transmitting tubes. The biggest problem was getting a "hard" enough vacuum.

Regards,
            Joe Cro N3IBX

Check out the two stage vacuum pump available from "United Nuclear". ;)

Joe

Great film! (My first time using YouTube)

Lot's of fun to watch. I would like to have one of the tubes they made.

Best regards
Stu

Fwiw, I ran across a Japanese site where the fellow was "rebuilding" gassy and larger sized vacuum tubes by making a new bottle for the top half, and then sucking them down, sealing and gettering. For some reason that wasn't exactly clear his envelopes were somewhat larger than the originals.

Seemed to me to be something maybe worth setting up for - you could potentially recover the gassy tubes. Some tube perhaps could be disassembled and completely rebuilt, but that's much more tricky.

Also, FYI, you need to really really suck hard to get the required vacuum for a good tube. The mechanical pump followed  by the diffusion pump is the usual method...

The smaller "receiving" tubes were made in a semi automated process on a machine called a "Sealex".
The Sealex took the parts in on a large revolving turntable and did all the processes from taking the assembly, putting the pins on, adding on the envelope, and sucking it out, etc... that's how they were able to make the little tubes in the millions.

Tubes like the larger types, 211, 845, etc... were made essentially in small batches by hand.

I saw the remnants of the United factory in Jersey about a decade back - all of those tubes were made in small batches, and mostly by hand. What was left of the company was still selling glass  and had a large room full of bins of tube parts - bases, pins, caps, ceramic and mica parts, stuff you need to make tubes.

           _-_-WBear2GCR

Joe, don't forget to test your new triodes after assembling, like this guys do:

http://www.youtube.com/watch?v=5CfpnLEssR0

They are also known as "Monitor Top (http://www.antiqueappliances.com/monitor_top_refrigerators.htm)" fridges.  The compressor unit on the top is said to resemble the turret on the USS Monitor (http://www.history.navy.mil/photos/sh-usn/usnsh-m/monitor.htm), one of the first ironclad ships used in warfare.

Mine was built in about 1930.  It was made by General Electric, and uses sulphur dioxide as refrigerant.

It worked until a couple of years ago.  Now, if I start it up, it cools for about a half hour, then I can hear something make a noise inside the compressor, and although the motor continues to rotate, it stops cooling.  I suspect a seal has gone bad in the compressor, and that the noise occurs when the seal fails and releases the pressure.

Sulphur dioxide is extremely nasty stuff, so I have made no attempt to open the sealed unit to repair it.  Not sure if there are any refrigeration mechanics who would tackle the job. I would  love to get the thing going again.  It made a FB OM beer cooler.

Tolly,
       I almost fell on the floor laughing when I saw that video!

      It only goes to prove that there are two types of people:
      Smart Fellers, and Fart Smellers.
      The type of person testing the PC board is the obvious!

      Best Regards and good hearing from you!
                                                               Joe Cro N3IBX 

Don,
     That's precisely why I would want one, to make a FBOM OldBuzzardly beer cooler.

     I wasn't sure what the refrigerant was, and thought it was probably ammonia. Both ammonia and sulphur dioxide are both nasty stuff, not to be taken lightly.

Does it have a recharge/evacuation tap on it to release the refrigerant into a sealed bottle like an old 30 lb container of R12,R22, etc? That might be one way of safely evacuating the system until you could get a new compressor, or a seal kit to replace the old one.

I wonder if there was a conversion kit to replace the sulphur dioxide with R22? A rough guess would be that you'd have to replace the receiver-dryer-accumulator, along with the refrigerant. I don't know what pressure sulphur dioxide was used in their systems. I guess you'd have to find someone who worked on them at one time to get more information on how to repair it. Somewhere, someplace, there has to be someone who has worked on them.

Best Regards and hope you get it going again someday.
                                                                            Joe Cro N3IBX

Hello All,
           I found an interesting website at:  http://www.6moons.com/industryfeatures/etf06/etf.html
           It's the website of the "European Triode Festival", apparently held once a year.
   
           If you found the "making of a triode" interesting, I think you'll appreciate the above website.
           Best Regards,
                             Joe Cro N3IBX

I especially liked the audio reproducing setup they had:

(http://img227.imageshack.us/img227/2729/systemed9.jpg)