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Thermionic valve projects?

Started by Peter Percival July 13, 2019
Here https://www.rapidonline.com/valves there are a variety of 
thermionic valves.  Where can I find projects that utilize them?  I'll 
also need a HT power supply.  Any thoughts?

-- 
"He who will not reason is a bigot;
he who cannot is a fool;
he who dares not is a slave."
  - Sir William Drummond
On Sat, 13 Jul 2019 15:36:21 +0100, Peter Percival wrote:

> Here https://www.rapidonline.com/valves there are a variety of > thermionic valves. Where can I find projects that utilize them? I'll > also need a HT power supply. Any thoughts?
EHT transformers are getting few and far between at rallies these days. If you can find say a 240-4kV tranny at 250mA you're all set. But valve action starts at much lower voltages (sub 100VDC) so you don't *have* to splash out on some awesome transformer just for experimenting with. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Cursitor Doom wrote:
> On Sat, 13 Jul 2019 15:36:21 +0100, Peter Percival wrote: > >> Here https://www.rapidonline.com/valves there are a variety of >> thermionic valves. Where can I find projects that utilize them? I'll >> also need a HT power supply. Any thoughts? > > EHT transformers are getting few and far between at rallies these days. > If you can find say a 240-4kV tranny at 250mA you're all set. But valve > action starts at much lower voltages (sub 100VDC) so you don't *have* to > splash out on some awesome transformer just for experimenting with.
Noted. What now? :-) -- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
On Sat, 13 Jul 2019 22:40:44 +0100, Peter Percival
<peterxpercival@hotmail.com> wrote:

>Cursitor Doom wrote: >> On Sat, 13 Jul 2019 15:36:21 +0100, Peter Percival wrote: >> >>> Here https://www.rapidonline.com/valves there are a variety of >>> thermionic valves. Where can I find projects that utilize them? I'll >>> also need a HT power supply. Any thoughts? >> >> EHT transformers are getting few and far between at rallies these days. >> If you can find say a 240-4kV tranny at 250mA you're all set. But valve >> action starts at much lower voltages (sub 100VDC) so you don't *have* to >> splash out on some awesome transformer just for experimenting with. > >Noted. What now? :-)
Wind your own plate transformer? Takes a little time to build a small winder but you're looking for a project, right? Pick the right one to scavenge and you'd just be winding the secondary. Filament transformers or DC power supplies are easy enough to find. I wound a 1 KVA Induction coil/transformer with some 13 miles of 32 AWG in the secondary. Took about a month, but I'd already built a winder for Tesla coils and modified it to wind multi-layer bobbins. You can always kludge together some combinations of isolation or "control" transformers to generate the HT required. It may take some knowledge and effort to make a switch mode supply or modify and existing one. Buy it? http://www.hammondmfg.com/300series.htm You aren't the only one in the world who wants to do this, so Google will turn up some things. Do it yourself tube type guitar amps are pretty popular...
On Sat, 13 Jul 2019 22:34:00 -0400, default wrote:

> I wound a 1 KVA Induction coil/transformer with some 13 miles of 32 AWG > in the secondary. Took about a month, but I'd already built a winder for > Tesla coils and modified it to wind multi-layer bobbins.
I admire your determination! I have a screw-cutting lathe which is ideal for this kind of thing. I can just stand there with a reel of wire putting a little tension on it as it gets unwound and a short time later, a *perfectly* spaced coil emerges. The OP could also try microwave oven transformers. He'd have to re-wind one as they're not much use as they come. But the *are* next to free to come by from your local recycling centre and ideal for experimenting with. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
On Sun, 14 Jul 2019 08:45:57 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

>On Sat, 13 Jul 2019 22:34:00 -0400, default wrote: > >> I wound a 1 KVA Induction coil/transformer with some 13 miles of 32 AWG >> in the secondary. Took about a month, but I'd already built a winder for >> Tesla coils and modified it to wind multi-layer bobbins. > >I admire your determination! I have a screw-cutting lathe which is ideal >for this kind of thing. I can just stand there with a reel of wire >putting a little tension on it as it gets unwound and a short time later, >a *perfectly* spaced coil emerges. >The OP could also try microwave oven transformers. He'd have to re-wind >one as they're not much use as they come. But the *are* next to free to >come by from your local recycling centre and ideal for experimenting with.
I'd spend evenings watching TV and winding. With every layer I'd coat the wire with varnish and have to wait for it to dry. I had a turns counter and was coming up 10% short of the theoretical or nominal turns-per-inch so I increased the layers to compensate. By measuring the resistance, the secondary was ~300 feet over my calculations. The idea of microwave transformers is a good one. I notice they've begun welding the laminations in a strip along one side. But one of those cheap angle grinders from Harbor Freight would make quick work of that for disassembly. The weld is probably to keep the laminations from buzzing, but one upside is there's no varnish to glue the laminations together. And he says nothing of what he wants to build, chances are it wouldn't require the iron of a MOT to carry the VA required. Then too we had some Delco car radios back in the stone ages that used 12V for the plates of the tubes and a big old (Germanium PNP) transistor for the output with a small tapped inductor to match impedance. Several tube radio schematics and a few that use 12V for the plate supply: http://makearadio.com/tube/tube-radio-schematics.php another https://www.nutsvolts.com/magazine/article/may2015_Whipple Tubes to do the magic and transistors for the heavy lifting.
On Sun, 14 Jul 2019 07:56:06 -0400, default wrote:

> https://www.nutsvolts.com/magazine/article/may2015_Whipple > > Tubes to do the magic and transistors for the heavy lifting.
Great project idea, but there's a dastardly IC lurking in there! I'm a bit puritanical when it comes to this kind of thing so if I were to build it, which sadly I don't have time to do, it would have to be *all* discretes for me, I'm afraid. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
default wrote:
> On Sun, 14 Jul 2019 08:45:57 -0000 (UTC), Cursitor Doom
> > And he says nothing of what he wants to build,
That's a good point! It may be that I won't know until I get started, but how about Valve voltmeter; oscillators (Hartley, Colpitts,...); power supply; SW receiver. Suggestions grateful received.
> chances are it wouldn't > require the iron of a MOT to carry the VA required. Then too we had > some Delco car radios back in the stone ages that used 12V for the > plates of the tubes and a big old (Germanium PNP) transistor for the > output with a small tapped inductor to match impedance. > > Several tube radio schematics and a few that use 12V for the plate > supply: > > http://makearadio.com/tube/tube-radio-schematics.php
There's plenty there that looks doable by a beginner.
> another > > https://www.nutsvolts.com/magazine/article/may2015_Whipple > > Tubes to do the magic and transistors for the heavy lifting. >
-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
On Mon, 15 Jul 2019 15:14:11 +0100, Peter Percival
<peterxpercival@hotmail.com> wrote:

>default wrote: >> On Sun, 14 Jul 2019 08:45:57 -0000 (UTC), Cursitor Doom > > >> >> And he says nothing of what he wants to build, > >That's a good point! It may be that I won't know until I get started, >but how about > >Valve voltmeter; oscillators (Hartley, Colpitts,...); power supply; SW >receiver.
I'd stay shy of the valve voltmeter, that would be fairly daunting even back in the day. https://tinyurl.com/yy56t4nl is the schematic for RCA's "VoltOhmyst." Good luck sourcing those multilayer wafer switches or a nice panel meter that you could make a scale for... Likewise the oscillators are easily doable, but what's the point? Just to look at the trace on an oscilloscope? You could, of course, build a small AM or FM transmitter based on an oscillator, being mindful of the regulations you might run into. In the US most of that stuff falls under part D of the FCC regulations, and even then you aren't allowed to interfere with other services. Check out "phono oscillators" if that's your thing. Power supplies used tube types 5Y3, 5U4, 6X4 if my memory serves, they often used center tap full wave bridge circuits and made use of the common cathode running on it's own dedicated filament winding (which was often floating at the HV potentials) Much easier and cheaper to use rectifier diodes today. Even the purist "audiophiles" stoop to using solid state rectifiers in their tube circuits. The HV source itself can be generated with a high frequency transistor oscillator too; you don't absolutely need a "plate transformer," unless it is for aesthetic reasons. A lot of the old designs ran directly off the power lines and used no isolation transformers. In those circuits they used tubes that had high voltage filaments and the filaments were wired in series. http://www.angelfire.com/electronic/funwithtubes/AA5-1.html
> >Suggestions grateful received. > >> chances are it wouldn't >> require the iron of a MOT to carry the VA required. Then too we had >> some Delco car radios back in the stone ages that used 12V for the >> plates of the tubes and a big old (Germanium PNP) transistor for the >> output with a small tapped inductor to match impedance. >> >> Several tube radio schematics and a few that use 12V for the plate >> supply: >> >> http://makearadio.com/tube/tube-radio-schematics.php > >There's plenty there that looks doable by a beginner.
Bear in mind some of those schematics use some truly ancient tube types. Good luck finding some 30 series valves, for instance... or sockets to put them in. But I do agree, there's a lot fun stuff there to tinker with. Super-regenerative radios worked very well. They may have lacked the selectivity of super-het designs but they were sensitive and used far fewer parts. You mention beginner and to me that looks like a good place to start.
> >> another >> >> https://www.nutsvolts.com/magazine/article/may2015_Whipple >> >> Tubes to do the magic and transistors for the heavy lifting. >>
There may be some kits available. There's a wealth of information on line for old radio and audio circuits using valves. Ebay phono oscillator kit (kits - scroll down too) https://tinyurl.com/y32tbevv There's several tube type audio kits.
default wrote:


> And he says nothing of what he wants to build, chances are it wouldn't > require the iron of a MOT to carry the VA required. Then too we had > some Delco car radios back in the stone ages that used 12V for the > plates of the tubes and a big old (Germanium PNP) transistor for the > output with a small tapped inductor to match impedance. > > Several tube radio schematics and a few that use 12V for the plate > supply:
Where is a good place to buy such things?
> http://makearadio.com/tube/tube-radio-schematics.php > > another > > https://www.nutsvolts.com/magazine/article/may2015_Whipple > > Tubes to do the magic and transistors for the heavy lifting. >
-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond