DIY Triodes

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DIY Triodes

Postby George Schmermund » Sun Dec 13, 2015 7:53 pm

I've been amusing myself with DIY triode construction related to simple and regenerative radios lately and have now decided to move into amplifier tubes. The radio tubes are similar to the early Audion style along with some 1920's cylindrical styles. They work well for their intended purposes, but the challenge now is to make a few that have some power handling capability. Nothing big, but still able to output maybe 2 or 3 watts to start with. I'm fascinated with the SET amps that I've been reading about lately.

Has anyone on this board considered fabricating their own triodes? I'd like to compare notes with anyone who has.
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Re: DIY Triodes

Postby Geek » Sun Dec 13, 2015 10:26 pm

There's a few with the engineering setup to play around with that. Consistensy is a pipe dream, but it's for educational purposes mainly.

I remember back in the old Radio-Electronics some dude made his own diodes by re-purposing light bulbs by adding an anode. Efficiency sucked, but hey, an educational article came from it ;)

Check out YouTube.

Cheers!
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Re: DIY Triodes

Postby burnedfingers » Mon Dec 14, 2015 5:50 am

George you must have a lot of free time and amusement of some type must be at a minimum for you to take on such a task. Geek mentioned the article and its worth viewing. I wouldn't hold any high hopes of making something that is able to put out a few watts of power. Instead you may want to settle for a couple of used #45's to play with.
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Re: DIY Triodes

Postby George Schmermund » Mon Dec 14, 2015 2:58 pm

Guys - Thanks for your input about making DIY triodes. I have to confess that I have the same thoughts about people who make their own jewelry. It seems rather silly to collect the tools and materials and then spend the time making something homebrew when they could just go to a jewelry store and buy something nice off the shelf and be done with it. Go figure.

Anyhow, I try to make room for those people who are always doing weird stuff. If nothing else, it's another low form of amusement for me to watch them spin their wheels!

I'll post some of the results relating to this current triode boondoggle of mine and offer it up as light entertainment for the rest of you. Who knows, maybe there will be others that will gain an interest in trying the same project?

Keep your filaments hot and your anodes cool!
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Re: DIY Triodes

Postby George Schmermund » Mon Dec 14, 2015 7:09 pm

Based on the assessments of Mr. Geek and Mr. Burnedfingers, It would seem that my best course of action right now would be to just start the folly and get it over with. Since I'm a veteran at reinventing wheels (lots of them), I think I'll jump right in!

I don't have any #45 tubes to play with so I'll use what I have in the junk box. Good fortune has bestowed upon me a box of #26 tubes from a recent eBay indiscretion. They're quite anemic by their nature, but they appear have good bones for starting my Frankenstein experiments. I'll make an assumption that the short coming of the #26 compared to the #45 (as recommended by Mr. Burnedfingers) is mostly in the power that can be pumped into the filament and not the ability of the anode to safely dissipate 1 or 2 Watts.

Based upon this off the wall assumption, I'll give one of the #26's a lobotomy and transplant a steroid enhanced filament of the thoriated tungsten variety deep into its innards. I never did like the coated filaments, anyway.

I'll do a sort of photo essay as things progress. Prepare for the shock of things to come!
Last edited by George Schmermund on Tue Dec 15, 2015 10:56 pm, edited 2 times in total.
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Re: DIY Triodes

Postby George Schmermund » Tue Dec 15, 2015 8:16 pm

The first thing needed to make a Hot Rod out of a #26 tube is to expose all of its private parts. This tube is going to be sacrificed for exploratory surgery. It's an easy job to cut off the bulb and expose the innards for a proper dissection. I want to make some physical measurements on the construction and examine the materials that were chosen to make various parts. As can be seen in the photos, this triode is simplicity itself. It won't even be a challenge to get some extra horsepower out of it.

I still need to make some dimensional measurements, but this design is pretty much plain vanilla as far as triodes go. More to come soon!
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Re: DIY Triodes

Postby George Schmermund » Sat Dec 19, 2015 7:48 pm

Now that the #26 triode has been dismantled it's time to finish the measurements and proceed to the creation of a new tube. The photos show the basic layout of the new parts that will be used. I'll salvage the old plate assembly and replace the rest of the #26 elements due to their restrictive design limitations. As can be seen, the new grid incorporates a finer pitch and the filament to grid spacing is wider. The grid wire it's wound with is gold plated molybdenum. This wire is more desirable because of it's low secondary electron emission. The posts are also improved because of their larger diameter and their high copper content which will improve the thermal conductivity for heat transfer down to the Kovar pins that they will be attached to.

The coated filament is being replaces with a multi-strand, helical wound, thoriated tungsten type of my own design. After carburization, this filament will far outlast the oxide coated type and still provide copious emission. Also, it will not sputter or evaporate barium onto the grid wires and cause undesirable high emission from same.

The old style inline pinch will be replaced with a button pinch that I prefer to work with as a stem assembly. All of the glass is now upgraded to borosilicate. This type of glass makes building vacuum tubes easy.

As an aside, I couldn't find the article that was referred to me buy Mr. Geek and Mr. Burnedfingers. Maybe someone could provide a link.
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Re: DIY Triodes

Postby burnedfingers » Sun Dec 20, 2015 5:55 am

Simply google "Making your own vacuum tubes" and in less that 5 seconds a number of them will pop up. There is a french video out there to watch and this guy makes his tubes from scratch.



I hope you didn't kill a good #26 in your effort to take a tube apart. ;)
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Re: DIY Triodes

Postby George Schmermund » Sun Dec 20, 2015 1:53 pm

Mr. Burnedfingers - I'm well aware of the work done by Claude Paillard, Ron Soyland, et. al. My request was for a link to the magazine article that you and Mr. Geek specifically referred to as a good source of information about DIY diodes. I apologies for my inability to communicate clearly. I will try to choose my words more carefully in the future.

As for the demise of a #26 triode in my misguided effort to improve its performance by re-engineering it, I will refrain from posting any more graphic details about the extent of the brutality that I seem to be capable of. My only excuse for such behavior is the I must have watched too many episodes of Dexter.
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Re: DIY Triodes

Postby burnedfingers » Sun Dec 20, 2015 2:40 pm

Mr George,

You could hold my attention better with the calculations your using to "re-design the 26". So far I'm not really impressed with the lathe and micrometer pictures or the ability to properly dial in the 4 jaw chuck on the lathe. Still, I must admit I see no logic in trying to make something that is easily obtainable at a reasonable price. What I see so far is wasted time and effort on your part that will produce absolutely nothing of any value. But then again this is strictly my opinion and would guess one that isn't shared by those that are easily amused. If you plan on making the tube 100% from scratch and produce measurements that will prove that your engineering efforts are of some value I will sit back in silence and eagerly await your final product of engineering genius.
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Re: DIY Triodes

Postby George Schmermund » Sun Dec 20, 2015 3:05 pm

Mr. Burnedfingers - Thank you for your informed opinion, but I'm really not that interested in holding your attention. I'm just putting my bread on the waters. I do appreciate you volunteering to take a vow of silence, though.
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Re: DIY Triodes

Postby IceFyre13th » Tue Dec 29, 2015 10:39 am

George, ignore burnedfingers....I myself find this extremely interesting and cant wait for more updates on your progress
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Re: DIY Triodes

Postby Auricle » Tue Dec 29, 2015 4:41 pm

..I myself find this extremely interesting...


I second that.

Thanks George for your posts!
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Re: DIY Triodes

Postby George Schmermund » Thu Dec 31, 2015 1:04 pm

There's no shortage of construction projects to work on if you want to make vacuum tubes. One of the primary tools needed to advance from using epoxy sealing to doing total glass sealing of the stem to the envelope is a glass lathe. To that end I've re-purposed a Harbor Freight mini wood lathe as the foundation for a DIY glass lathe. This project has taken longer than I'd hoped, but I'm easily distracted by other challenges and have to apply myself as the spirt moves me.
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Re: DIY Triodes

Postby George Schmermund » Fri Jan 01, 2016 3:08 pm

OK, I'll admit that building your own glass lathe is sort of like preaching to the choir when you're on a DIY Tube forum, but I have to start somewhere.

As you well know there are other tasks that need to be done before the tube parts can be assembled. these parts must be very clean to be able to achieve and maintain a high vacuum once the envelope is sealed to the stem assembly. For this job I've approached the need for a final cleaning of the parts with a simple vapor degreaser. Some of you may have approached this requirement through different means, but I'll show you what I've cooked up (pun) with materials that were around the shop.

I know that there is a 'ho hum' factor that needs to be applied here, but these jobs still need to be attended to. Those of you who have transcended these entry level projects might want to just wait until I catch up. There are several steps to go before 'first light'.

Here's how the vapor degreaser looks at this point:
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