Film-Tech Forum ARCHIVE: Making of a triode valve (vacuum tube).

This is topic Making of a triode valve (vacuum tube). in forum Film-Yak at Film-Tech Forum ARCHIVE.

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Posted by Stephen Furley (Member # 1277) on 01-06-2008, 03:09 PM:

Just found a link to this video on alt.engineering.electrical. It shows the making of a triode valve by hand, and may be of interest to some of you here.

web page

Posted by Gerard S. Cohen (Member # 994) on 01-06-2008, 04:25 PM:

Thanks for that entertaining and instructive video. There's no limit, it seems, to what a true craftsman can do!

My father had told me that radio vacuum tubes used to be sent back to the factory for remanufacturing when they failed from use, and this was confirmed when I found printed enclosures that were once packed with new tubes (RCA, I think.) I couldn't understand how this could be possible until I saw this video.

I have great respect for those with the multiple skills (and equipment) needed for such tasks. In contrast, I tried to make a folded paper (origami) crane offerering. I couldn't find anyone who could show me how, so I went to google.com and then ask.com and printed four different instruction charts, one requiring 25 folds, but neither my wife, our receptionist nor I could succeed in making one. Happily my daughter visited and made one for me, which I will offer at the next opportunity.

Posted by Mark Gulbrandsen (Member # 72) on 01-06-2008, 04:30 PM:

That is one of the most amazing things I've ever seen. [thumbsup]

Posted by Robert W. Jones (Member # 4228) on 01-06-2008, 04:33 PM:

Great video. And they still rock for audio applications!

Rob

Posted by Monte L Fullmer (Member # 2797) on 01-06-2008, 04:35 PM:

Quite interesting. I bet he can make his own xenon bulb... - Monte

Posted by Jim Cassedy (Member # 4115) on 01-06-2008, 04:48 PM:

Somewhere around here I have some old radio magazines from the 1920's and I recall seeing advertisements in the back for places that would "re-build" vacuum tubes. I had an uncle who collected antique Christmas tree lights that were in different figurene shapes. Santas, Snowmen, Trees, etc. I remember when I was a kid he used to take them to some old guy in Brooklyn NY when they burned out who would re-build the lights and somehow put new filaments inside to make them work again. (This was almost 40 years ago) Similar but not as exacting work as rebuilding a vacuum tube.

Posted by Tim Reed (Member # 137) on 01-06-2008, 06:08 PM:

Excellent! Thanks, Stephen!

Btw, who was it I heard of, not too many years ago, who got all the old RCA 6L6 manufacturing equipment?

Posted by Mark Gulbrandsen (Member # 72) on 01-06-2008, 06:15 PM:

Western Electric is still producing brand new tubes of many of their older designs... They saw an eventual need to be able to supply vaccum toobes down the road and they kept the entire factory in mothballs for well over two decades. Undersea transmission lines from what I understand are still all vaccum toobe amplified. They have also bought the right to produce the venerable Gold Lion KT-88 power Pentode... they are a mere $350.00 a pop!

http://www.westernelectric.com/#

One thing is for sure... they have definately got some of the coolest logos in existance!

Mark

Posted by Matthew Bailey (Member # 601) on 01-06-2008, 07:28 PM:

Found on You Tube a 1950's Telefunken tube ad. click here

Posted by Monte L Fullmer (Member # 2797) on 01-06-2008, 08:10 PM:

That's a neat Telefunken ad .. and noticing the opera singer singing into a "Neumann bottle" mic (which prob had the Telefunken trademark on it..). -Monte

Posted by Aaron Sisemore (Member # 145) on 01-06-2008, 10:43 PM:

quote: Mark Gulbrandsen
They [Westrex] have also bought the right to produce the venerable Gold Lion KT-88 power Pentode

Apparently, this is not the case anymore (that site was last updated in 2005). Apparently New Sensor (the Sovtek/EH people) has those rights now, along with the design and trademark rights for Tung-Sol and Mullard. You can buy the Russian-made Gold Lion KT88 right now. (and for less than Westrex was charging for them) ... [Roll Eyes]

...and the KT88 is a beam tetrode, not a power pentode. [Smile]

-Aaron

Posted by Robert W. Jones (Member # 4228) on 01-06-2008, 10:52 PM:

The 6L6's are indeed still in demand. My Son's band uses them in their amplifiers. Can't beat older technology in some cases.

Posted by Jeff Stricker (Member # 224) on 01-07-2008, 06:27 AM:

Lots of the more popular tube types are being manufactured in China under various old-time brand names. Beware of poor quality. I had a "Penta" China manufactured 3-500Z that failed at around 500 hours of filament time. In my very conservatively operated RF linear amp, the tube runs at less than 5% duty cycle (5% key down time). Welds holding plate structure in place failed on one side allowing plate to tilt and touch the grid [Mad]

POOF! A USA Eimac tube will run thousands and thousands of hours in this application.

Posted by Stephen Furley (Member # 1277) on 01-07-2008, 08:12 AM:

I've just had another look at the video, and there's something a bit odd about the triode he's making; it doesn't seem to have a getter.

Posted by Jack Ondracek (Member # 1466) on 01-07-2008, 10:56 AM:

quote:
My father had told me that radio vacuum tubes used to be sent back to the factory for remanufacturing when they failed from use,

High power broadcast transmitting tubes still are. There are two or three companies in the US that do this. The cost is about half what a new tube would run, and carries the same warranty as new.

I keep a couple of old AM transmitter going this way. The final tubes in one of them are no longer made, but you can rebuild 'em pretty much forever.

Posted by Richard Fowler (Member # 893) on 01-07-2008, 11:21 AM:

Some xenon bulb manufacturers will recycle usable components from D.O.A. bulbs....their is a lot of hand made work to those xenon "tubes".

Posted by Alan Plester (Member # 852) on 01-07-2008, 11:40 AM:

Watched & watched again, that is one of the most amazing vids i`ve seen in years, wonder how long that takes in real time?.

Posted by Stephen Furley (Member # 1277) on 01-07-2008, 12:23 PM:

Probably not that long once he's got the tools set up. You see all three electrodes being made in pretty much real time; most of the metalwork is spot welded, which is a quick process. You see quite a bit of the glasswork though obviously it takes a bit longer for things to heat up and cool down than you see. I'm not sure how long the electrodes have to spend in the various baths, and the pumping and bombarding would take a while, though again I'm not sure how long.

Sealing metal electrodes into glass is tricky, as most metals expand considerably more than glass does, and therefore can crack the glass as they heat up.

Posted by Louis Bornwasser (Member # 3063) on 01-07-2008, 01:21 PM:

6L6 and their clones: 6CA7, KT-88, SC-1000m have passed into the public domain years ago. Most tube types were "bartered" between manufacturers. Example GE 6CA7s were actually Amperex (Holland) The rest were probably Mullard G.B.

FYI: the original 6L6 was a coproduction of RCA and Motiograph, just prior to WW2; they had a contractual 5 year non-compete and after the war, everyone had them.

BTW: We made oscilloscope tubes in high school physics class in the bottom of a flask with a double stopper. Crude, but it worked. Louis

Posted by Stephen Furley (Member # 1277) on 01-07-2008, 01:58 PM:

Probably not that long once he's got the tools set up. You see all three electrodes being made in pretty much real time; most of the metalwork is spot welded, which is a quick process. You see quite a bit of the glasswork though obviously it takes a bit longer for things to heat up and cool down than you see. I'm not sure how long the electrodes have to spend in the various baths, and the pumping and bombarding would take a while, though again I'm not sure how long.

Sealing metal electrodes into glass is tricky, as most metals expand considerably more than glass does, and therefore can crack the glass as they heat up.

Posted by Aaron Sisemore (Member # 145) on 01-07-2008, 02:18 PM:

quote: Louis Bornwasser
GE 6CA7s were actually Amperex (Holland) The rest were probably Mullard G.B.

While it is true that the American manufacturers stuck their brand name on the Mullard and Amperex 6CA7/EL34s, GE actually made their own 6CA7 (the Fat Boy style) in Owensboro, and Sylvania also made one domestically. The GE ceased production in early 1993, and the Sylvania (later PhilipsECG) ceased ca. 1987.

-Aaron

Posted by Mark Gulbrandsen (Member # 72) on 01-07-2008, 02:39 PM:

quote: Jack Ondracek
High power broadcast transmitting tubes still are. There are two or three companies in the US that do this. The cost is about half what a new tube would run, and carries the same warranty as new.

You're right. We used to send the Klystrons back to Varian in Salt Lake City for rebuilding. Every time the tower was struck by lightning(John Hancock building) it would erode away some grapite pieces in the tube which had a similar function to a grid in a regular tube... eventually it would fail. Rebuild cost about 150K every time... Te Aural klystron was only run at 1/3 power and it always lasted the longest of the three.

Mark

Posted by Will Kutler (Member # 770) on 01-07-2008, 09:57 PM:

My Baby...my 1938 RCA 816K uses 2 6L6's in push-pull with a 12 inch electrodynamic speaker

Restoration is comming along ok. New custom-wound power transformer (thanks to 3rd party who damaged the original) from Heyboer Transformers using the original end caps. Need to have chassis and other sheet-metal parts replated so I can begin reassembly.

Posted by Bob Koch (Member # 1062) on 01-08-2008, 01:33 PM:

Louis; I built an amplifier when I was in hi school that had a 6F5 driving a single 6L6. This was quite awhile before the war1937-8]. I certainly never heard anything about Motiograph being involved with any development of any kind. They took over some WE Mirrophonic designs as WE was being escorted out of the film sound reproduction business.