Here
-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
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.
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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
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?
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...
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.
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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:
another
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.
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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.
There's plenty there that looks doable by a beginner.
-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
Where is a good place to buy such things?
-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
I don't know. You can find odds and ends and kits on ebay. But the people doing it today are filling an emotional need IMO. The effort and meticulous attention to detail suggests it's more a labor of love.
I've fixed a few old radios that people brought to me and it's a hunt to find parts for them.
Amateur radio swap meets are a good source of interesting stuff.
Search on boat anchor radio - those words, not the phrase
As a kid, I used to use a 90v battery for the plate supply. Opened it one day and it was 10 9v batteries! Remember Burgess Battery?
You sound surprised.
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Sometimes you never know what is actually inside a battery larger than the nominal 1.5 volts.
I have seen 9 volt batteries containing 6 cells that look about like aaa batteries and some that have 6 stacked flat caseless (wraped in plastic) cells. The old 6 volt lantern battery was 6 large 1.5 volt cells. I have not opened up the newer ones, but have seen youtubes where they have lots of AA or so cells in them.
For the latter, I though building my own would be a good idea. And if building one is a good idea then building two must be twice as good. Thus -
(a)
The worst that can happen is that I'll electrocute myself.
>-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
You'll find after a few years you just get used to it.
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That's one of those things that if you survive the first time, you never, ever, want to do it again. I like to put the power cord in my pocket when working on Tesla coils.
HV DC is probably worse than AC, but none of that stuff is to be taken lightly. Stay safe. You can be macho without being stupid.
I only know the weird stuff...
inverted tube as hi-Z electrometer
spacescharge tubes: B+ twelve volts
Lots of weird ancient projects, "The Experimenter" mag from 1925, in .pdf
Misc. tube-theory secrets
the Plasma Tweeter (v.t. power-osc w/rf arc)
X-ray strobe light
Sideview-style Magic-Eye tubes $1.25 each (phosphor-coated anode)
So much the better! Thanks.
-- "He who will not reason is a bigot; he who cannot is a fool; he who dares not is a slave." - Sir William Drummond
More weird tube circuits (pdf):
My favorite is the high-speed microwave beam-scanner based on reflecting the microwaves off of the sweeping electron-beam inside an oscilloscope CRT. (We forget that electron-clouds are a conductor. A SINGLE ELECTRON is a conductor: when exposed to a voltage, a current appears! Same with ions in a vacuum. A moving electron-cloud is a moving mirror for radio waves. So weeeeird.)
Also, page way down on this below, for lots of PDF booklets for tubes-hobbyists
That brings back some memories.
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