Vacuum tube blinkenlights - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 14, 2020, 03:35:25 pm
content: https://imgur.com/gallery/OF4jAxhEdit: Seven Tube LabsTim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 14, 2020, 05:19:18 pm
content: And the schematic, if curious:https://www.seventransistorlabs.com/Images/Tube_Shift_Register.pdfTim

author: TimFox
author_rank: Super Contributor
timestamp: November 14, 2020, 06:34:47 pm
content: About 45 years ago, I found that the 7407 open-collector high-voltage buffer was a good interface from TTL levels to the cathode of a 12AT7 triode with its grid grounded.

author: Gregg
author_rank: Super Contributor
timestamp: November 14, 2020, 06:42:22 pm
content: The Covid Boredom Force is strong here.Thanks for the effort to entertain the rest of us.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 14, 2020, 06:57:46 pm
content: Quote from: TimFox on November 14, 2020, 06:34:47 pmIndeed, or the 7406 if you like inverting. Some of the few 7400 still in production, and with good reason.Only downside is, the 7406 goes way faster than the 12AT7Tim

author: Pawelr98
author_rank: Regular Contributor
timestamp: November 15, 2020, 06:40:44 am
content: Quote from: T3sl4co1l on November 14, 2020, 06:57:46 pm12AT7/ECC81 is an RF double triode capable of going well into UHF frequencies.7406 can do what ? Few dozen MHz ?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 15, 2020, 11:34:53 am
content: The bandwidth in either case is 10s of MHz, whether baseband (resistive load with peaking) or RF (resonant, narrowband).Yes, the 7406 obviously can't reach the center frequency in the latter case.Another way to put it: the edge rate is comparable, for some amount of useful gain. (You can always load the plate with a very low resistance, and observe the response of ballistic electron flow -- the step response is a ns or so; but you don't get any gain.)Tim

author: TimNJ
author_rank: Super Contributor
timestamp: November 15, 2020, 04:34:35 pm
content: That’s pretty sweet. Did you just do it for fun? Can’t imagine there’s any relevant application these days?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 15, 2020, 05:08:13 pm
content: Fun, yes. Something to breadboard. Annoying that I only had four sockets-on-leads so I had to make up a few more...Tim

author: chris_leyson
author_rank: Super Contributor
timestamp: November 15, 2020, 06:36:32 pm
content: More tubes than TEK 581 distributed amplifier and that managed about 100MHz bandwidth with four 6DJ7 or E88CC dual triodes and a 7699 dual tetrode final. The 7699 might manage a few hundred MHz. Due to problems manufacturing CRTs with distributed deflection plates TEK dropped the bandwidth to 80MHz. Not the easiest of amplifiers to tune up I might add.http://w140.com/tekwiki/wiki/581#/media/File:Tek_581_vertical_output_amp.png

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 15, 2020, 08:48:50 pm
content: Yup. 6DJ8 has about double the performance of 12AT7, and then the distributed amp scales that up arithmetically -- the bandwidth per stage is the same limitation (about 20MHz in this case), but multiplied by five, they got a good 100(ish) MHz out of it.Also not to mention peaking in general, which offers a 30-200% increase in bandwidth, depending on complexity and desired flatness -- tricks of course which can be applied to any amplifying device if you like.Similarly, this VHF radio front-end I built, uses a 6688 to about 20MHz of bandwidth (e.g. the 88-108MHz FM BCB):It's double tuned (grid and plate), which extends the flat bandwidth further than a single-tuned case would give, in exactly the same way as peaking works for baseband circuitry. Downside? The gain isn't very much (I'm a bit uncertain what it is, actually; I mostly measure around 7dB, which hardly seems worth it!), and the maximum stable gain (for reduced bandwidth of course) is lower than for the single-tuned case. Which isn't so relevant here (the gain is quite low), but, the IF strip I built that follows it (which... I don't seem to have pictures of, for shame!), does run into that problem a bit (mostly a consequence of its relatively high center frequency, and suboptimal choice of tube; shielding and a little neutralization seems to have done the trick).Tim

author: Pawelr98
author_rank: Regular Contributor
timestamp: November 16, 2020, 10:35:11 am
content: Quote from: TimNJ on November 15, 2020, 04:34:35 pmTube stuff can run directly from mains and can interface with other high voltage circuits directly.Also will survive an EMP so if you need your christmas lights circuitry to survive a nuclear war then tubes is one of the ways to go.But then those big tubes are not practical for such applications.I have a couple of tiny rod tubes made in USSR. 1Z24B.1.2V 13mA directly heated pentode that can be satisfied by just 20-30V just fine.Those tubes do a decent job at frequencies up to HF, more than that and you'll need to toy around (some german guy made a whole FM radio using those).