Tube Radio Power Supply

Forgot the link to the power supply plans:

(note that nearly everything I'm going to say is from book learning, not practical experience. Size your grain of salt appropriately).

A type 80 would be period correct, but you'd have to get a transformer for it.

Regens were very picky about the power that they'd run off of -- you get all sorts of oddball power supply/radio interactions. Most designs that I've seen that use the 2V battery powered filaments use a pair of dry cells and a rheostat for filament (A) power and a 45V battery for B.

5 9-volt batteries, snapped end-to-end, is one of the accepted methods for powering one of these critters, and apparently has good life. Rechargeables should work fine, and save you $$ on batteries if you end up using the radio a lot.

--
Tim Wescott
Control systems and communications consulting
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I used 45-volt phone supplies in some of what I did, many years ago when I'd scrounge them from phone companies. They were a 'box', basically of AA carbon rod batteries soldered together. Those worked very well and lasted and I'd use two to get a 90V plate supply. I'd never tried to use stacked 9V, though. My memory is struggling, but I think I used 5U4s and 6AU4s for diodes, pulled from old tvs.

By the way, I gave away a box of tube pulls I'd collected that literally filled a 3' x 3' x 2.5' box to a radio club in the east, about a decade ago. Included very old tubes I'd collected back in

1965: including pulls from old WW II (1944 and after) radar units (sellenium rectifiers, selsyn motors, VR-150s, waveguides, ... lots of interesting things there.) Separately, a 4CX1000A I had also was sent to them.

I never did use the small, 2V filament tubes, though. Just 6.3/12.6V stuff as far as I recall. (Thinking about tubes reminded me that estimating grid leak resistor values was one of the early mysteries for me, since I had remembered reading that there was essentially no current so I just sat there scratching my head with ohms law and nothing to plug in for current and yet knowing that I needed to somehow bias it.)

Jon

But that sort of devolves to the fact that the regen is seen as a simple receiver, so nobody wants to complicate them.

Given that they are at times an oscillator, and the rest of the time often on the cusp of oscillation, it's always a surprise that few have treated them like oscillators. Obviously in the twenties or thirties the cost of components was a big factor, but in more recent decades parts have become cheap.

So you don't see voltage regulation on a regen, even though an oscillator would tend to have one. You wouldn't have an oscillator driving an antenna directly, well not in decades and decades, but it's seen as acceptable to connect the regen directly to the antenna. You'd not build an oscillator on something that wasn't mechanically stable, or use tiny wire for the oscillator coil, but that sort of thing becomes acceptable for a regen. Don't bother with DC on the filament (if it's a tube regen), because it's too much work; live with any modulation that comes from 60Hz on the filament.

Build it like the oscillator it is, using voltage regulation and isolation from the antenna and using a nice solid wire for the coil, along with multiple bypass capacitors and all the rest, and it's bound to help the overall useability of the regen.

Charles Kitchen, who's done quite a bit of work on solid state regens, going back to the original regen work and then trying to bring it into the solid state age, has put in at least simple regulators, the cost to the project is really insignificant.

Michael

Some of those designs from the '20s and '30s used _good_ components, at least for the day. There was much that wasn't understood about things like wire size, but much was, and was published in the amateur literature of the day.

Per my small stack of ARRL literature, amateur radio builders didn't discover the use of gaseous voltage regulator tubes until the early - mid thirties; even by then the regen was seen as a 'simple' receiver, to be replaced by a superhet as soon as you could afford it.

Was, back in the day when the bands weren't crowded. One is abjured not to now, at least by the ARRL.

I suspect that everything you have to say is on track technically, except for my above objections and/or apologies to your perceptions of prevailing opinions.

I also suspect that by the time you get a regen to _really_ work well you will be approaching superhet complexity, and probably with a really inscrutable circuit.

It'd be fun, though.

--

Tim Wescott
Wescott Design Services
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"Applied Control Theory for Embedded Systems" gives you just what it says.
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I've found another tube that hasn't got the amplfier section, which I didn't need, the 117Z4GT. Still has a 117v heater, so I don't need a transformer. I am going to build the whole thing in a plastic box for safety, with the tube sticking out the top. I might use binding posts for the B+ 45v, and filament (powered by two "D" Cells, with 18 ohm resistor).

Dave Australia

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Also, would it be OK to replace the .05 uF (ceramic) with a polyester capacitor? I can't seem to find any ceramics with 400 volts rating

That should work. You'll have crappy regulation with that circuit, and the 'natural' voltage of a capacitor-input supply like that is between the line voltage and line voltage times root-2, so 117V to 164V. They 'fix' that problem with R2 and R3, although at first blush I don't trust their specified power rating for R2 -- if you need 5W for R3, which is about the same value as R2 and carries less current, why can you get away with 2W for R2?

If you have any spare filament transformers around you can use one for a choke-input supply. With a single diode you should get around 45V with plenty of ripple; with another spare filament transformer you can pound the ripple down a bit.

A (fun) alternative if you have the circuits knowledge would be to replace R2 on with a regulated supply. You could go with something as simple as a neon light (or zener) connected to the grid of a triode (or base of a BJT), up to a fancy actively regulated supply using a couple of tubes or an LM723.

I'd start with what you're proposing, though, and go from there.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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Yabbut.

There's a specific safety rating for capacitors that go on the power line. I can't remember it, but basically for a 120V line you want to have a cap that's good to something like 630VDC (hopefully someone whose done this recently will jump in here).

For a home job in a fire proof enclosure, with the cap on the 'other' side of a transformer, 400V is probably OK -- but I didn't say that in any professional capacity, yer on your own for safety related stuff.

You _are_ going to fuse the input side, right?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

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Yes, what fuse rating should I use?

Thanks Dave Australia

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I'll probably experiment with regulation circuits when it's up and running.

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,, When modifying the circuit to output 45 volts, do I replace R3 with, for example 2800 ohms, if there is an output of 160v? Or do Ieave R3 in?

Thanks Dave Auustralia

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Is the 117Z4GT an 8 pin octal? Here:

Z4GT.pdf It looks like it says 6 pin octal.

Thanks Dave Australia

You juggle the values of R2 and R3 to get good regulation, low dissipation, and low ripple.

You want the highest value of R3 that'll get you by when the radio's connected.

Pay attention to dissipation.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
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Um uh, um.

No higher than the current capacity of the xformer primary, for sure.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Regular octal pattern, with two pins deleted. You can use a regular

8-pin socket, or if you plan on volume manufacture you can special order sockets with those holes blanked out.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html