1920s radio

A little homemade 1920s 1 valve set with direct heated triode (unmarked). I 've traced most of the circuit, looks very simple. Not tried to trace the m ain coil assembly with its 6 connections yet. The valve has a grid leak res istor for -ve bias without C battery. It runs high R phones, no speaker. 1s t question is what sort of HT voltage and/or anode current should I aim for ?

NT

Reply to
tabbypurr
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One triode from that era is the A415. The datasheet lists Va between 20 and

150V, saturation current of 30 mA and default anode current of 3 mA.
Reply to
Arid ace

Indeed, you need to know the tube value to be sure, but consider the cost of batteries of the day and thus the B+ is likely 45VDC or thereabouts.

In those days some people made their own B+ batteries - way back when I was a kid digging through attics in Toronto (mid 1960s) for old battery sets I found a couple of home-made lead acid batteries that were glass test tubes about 8 inches long mounted in a wooden box and there must have been 15 to 20 in each case. Wish I still had them as they were classic home-brew stuff which I always loved from the battery age of radio.

John :-#)#

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Reply to
John Robertson

** The "battery age of (tube) radio" extended well into the 1960s.

Popular "portables" of that era used a pair of 45V packs for B+ and a large 1.5V dry cell for tube heaters - all made by "Eveready".

Miniature 7 pin tubes like the 1S4 and 1R5 were used - along with a transformer supply for home use with a multi-finned selenium rectifier.

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..... Phil

Reply to
Phil Allison

Hello, and I once owned a Red case 4-tube (1R5, 1U4, 1U5, 3Q4) Westinghouse H-496P4 AM-band portable that used a 67.5 volt B-battery. The radio had a large speaker and sounded real nice but that B-batt was expensive. Sincerely,

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J. B. Wood	            e-mail: arl_123234@hotmail.com
Reply to
J.B. Wood

I've still got one of these, bought by my father in 1955:

It still works on mains (I doubt it would be possible to find a decent B126 90v battery today); I added a miniature earphone socket in the

--

Jeff
Reply to
Jeff Layman

That will, very likely, be an Armstrong-circuit regenerative radio based on a common tube of the day, and what comes immediately to mind is the O1A, a 4-pin triode and good performer.

Filament voltage is 5 VDC - polarity not critical. B+ will be 90 - 135 VDC Grid voltage will be -4.5 - -9 VDC

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Overall, those early triodes were not very efficient as compared to "modern " miniatures of the late 1940s and 1950s.

Note that this basic design often included a variety of plug-in coils for c onventional broadcast, SW and other bands as may have been available at the time. Keep in mind that 'official' regulation of land-based broadcast radi o did not start (have teeth) in the US until ~1927. And, pretty much every Tom, Dick, Harry, church, department store and other organization had its o wn radio station, not to mention thousands of amateurs. So, the concept of staying with any given 'band' was not regulated.

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

I've traced most of the circuit, looks very simple. Not tried to trace the main coil assembly with its 6 connections yet. The valve has a grid leak r esistor for -ve bias without C battery. It runs high R phones, no speaker.

1st question is what sort of HT voltage and/or anode current should I aim f or?

From all the replies it seems I don't know much, other than to set it for a n Ia of about 2-3mA. It's a 4 pin valve with a modern shaped envelope, so c ould be anything. I guess it's a dull emitter replacing the original bright . There's no filament rheostat.

The circuit details are different to the Armstrong version here

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-it's definitely a reaction set, no doubt there.

Apart from an input cap on the aerial there is NO other fixed cap anywhere in the circuit, so it's going to be horribly unstable, as if PFB on the edg e weren't unstable enough already.

I reckon it owes more to 19 teen design than to late 20s, so I expect a ver y early 20s set. I expect the ae coupling cap, tuning & reaction will all i nteract some - not to metion headphone wire position affecting feedback as well. It's gonna be a fun one to use.

I presume the coil has a separate winding for the ae, and 2 more winds for the tank & pfb. PFB is controlled by a small varicap.

It got rewired at some point with pvc. Can't imagine why. The connections a re all 2mm sockets, which seems anachronistic, but everything else is defin itely original.

There's an extra hand wound coil that's only connected at one end. Can't se e where it used to connect to. It connects to the ae input after the ae cap , and afaics the circuit ought to work fine without it in. Who knows.

The ae cap pretends to be something else, it's only marked as "the new and improved... stabilizer portable aerial... for better listen" and terminals are marked A & B. Will do some component testing later.

NT

Reply to
tabbypurr

Yeah, but I was talking about the time when the primary home radio was a battery set - prior to battery eliminators and the like...

I have a lovely (well, it was lovely at one time, the case needs all new leather) Radiola 24 which was an early 'portable' radio in my small collection. About the size of carry-on luggage these days. Cunningham C-299 tubes...

John :-#)#

Reply to
John Robertson

After you have handled or been around in the mid-five-figures worth of vint age radios, you will learn not to reason from the specific to the general.

Magic words here are:

1920s Home Brew Single tube

a) Suspend all other expectations, and deal with what is in front of you. O1A tubes come in several shapes, from globe to ST. I have seen one (1) "G" type as well, so anything is possible. There are also several other candid ates that would do, including an OO, 30 and 112 amongst others. Some would require a different filament voltage. But, the O1A is/was the go-to as they were very common, and much cheaper than the alternatives.

b) Variable capacitors are/were expensive relative to fixed caps. So, your home-brew hobbyist likely picked a fixed cap at some value between that spe cified for a variable cap.

c) Fixed caps are/were expensive relative to nothing - so your home-brew ho bbyist 'went without'. He/She (a great many of the earliest hobbyist were g irls/women - why? Most of the parts were made by women). He/She was probabl y listening to a nearby "torch" station with little or no competition, so t argeting to a specific frequency would be typical.

d) At the time, coils were either wound by the hobbyist or purchased to a s pecific range. If no plug exists, then your hobbyist was uninterested in, o r could not afford that option.

e) At the time, there was no 'set standard' for radio parts, connections, h ardware nor much of anything else. The typical hobbyist, working on-the-che ap as this one clearly was, would use what was lying around. Which might ex plain some oddball stuff.

f) Note that the standard for *cheap* wire at the time was rubber/gutta-per cha insulation. Which would crumble to dust in short order. So, PVC is no s urprise.

On that one-handed coil - are there any taps on it? Commonly, a poor-man's SW or Airplane frequency coil would be done that way - one end fixed, and then tapped to the standard antenna for the alternate.

Summing up, you have the equivalent of a fox-hole radio created with as few expensive parts as possible, following the general idea of the Armstrong c ircuit, which was 'all the rage' at that time.

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

The people on this forum will be very knowledgeable and happy to help. >

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Mikek

Reply to
amdx

I had an early 1920s Crosley radio. It had two RCA WD12 tubes which were retained into their sockets by a rod that projected out of the tube that was locked into a groove in the tube socket. Tuning was by a coil on a shaft that one pulled toward or away from a stationary coil. A multi contact rotary switch selected segments of the AM band. It used 3 batteries; one for B+, one for the filaments and one for grid bias. It picked up the 50000 watters in the northeast USA at night. When I came back home from my first year at a midwest university, one of my brothers had stolen it and I never saw it again.

Reply to
Chuck

ntage radios, you will learn not to reason from the specific to the general .

One can't always rule out an amateur builder working to their own outdated technical knowledge. But they clearly know enough to get a radio working, a nd it's not much more leap to bring the tech up to date.

G" type as well, so anything is possible. There are also several other cand idates that would do, including an OO, 30 and 112 amongst others. Some woul d require a different filament voltage. But, the O1A is/was the go-to as th ey were very common, and much cheaper than the alternatives.

useful to know.

r home-brew hobbyist likely picked a fixed cap at some value between that s pecified for a variable cap.

The one fixed cap on the ae input is in series with a variable cap! I suspe ct the variable was added later. The other controls are nice & symmetrical then then ae input VC is stuck round the side.

hobbyist 'went without'. He/She (a great many of the earliest hobbyist were girls/women - why? Most of the parts were made by women). He/She was proba bly listening to a nearby "torch" station with little or no competition, so targeting to a specific frequency would be typical.

My homemade '24 set has lots of caps. But this one is, as you rightly concl ude, a total cheapie job. The cabinet is nice but open the lid & it's clear ly ill fitted pieces untidily glued together. The rest is similar.

Caps however were almost free. Take some paper & a little foil, tie with co tton & wax it and minutes later you have a cap. Any electronics book of the day explains this. A different history piece I have includes an HV cap mad e with plywood as the dielectric. I've never seen any graphs on how they pe rform :) I guess it's still cellulose.

specific range. If no plug exists, then your hobbyist was uninterested in, or could not afford that option.

hardware nor much of anything else. The typical hobbyist, working on-the-c heap as this one clearly was, would use what was lying around. Which might explain some oddball stuff.

It has 3 knobs, all clearly of the era but all different. I don't know for sure it was that way originally but it would not surprise me.

ercha insulation. Which would crumble to dust in short order. So, PVC is no surprise.

I thought bare wire was the usual thing to wire up radio internals then.

"Waldo Semon and the B.F. Goodrich Company developed a method in 1926 to pl asticize PVC by blending it with various additives. The result was a more f lexible and more easily processed material that soon achieved widespread co mmercial use. " So it could even be original wiring, though that's not likely.

's SW or Airplane frequency coil would be done that way - one end fixed, an d then tapped to the standard antenna for the alternate.

no taps. Looks like it was hand wound round a convenient round object, some sellotape added to keep it together & that was it. It has its own custom m ounting made from the same material as the cabinet, so probably was fitted from the start.

ew expensive parts as possible, following the general idea of the Armstrong circuit, which was 'all the rage' at that time.

Well, it's a fair bit better than a foxhole set but yes it definitely incor porates some 'whatever' parts, and some not.

NT

Reply to
tabbypurr

There were kit radios of the day that used simple tinned wire. I have one, a Mercury Super Ten kit (10 'peanut' tubes - superhet) around here somewhere, but I don't think they are that uncommon.

John :-#)#

Reply to
John Robertson

PVC insulation on wires wasn't used until the '40s and was mostly used by the Government for WWII production. And even at that, there was plenty of wire that was rubber, although it was covered in braided cotton.

The standard wire in the 20's was either rubber covered, bare or "push back" which was solid copper with a spun cotton or silk covering that could be Just pushed back" so no fuss to expose the ends of the wires.

Absolutely NOT likely at all in the '20s.

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Reply to
Fox's Mercantile

DCC. The homemade coil is enamelled rather than DCC.

Reply to
tabbypurr

Probably intended for a 67 V B battery.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

). I've traced most of the circuit, looks very simple. Not tried to trace t he main coil assembly with its 6 connections yet. The valve has a grid leak resistor for -ve bias without C battery. It runs high R phones, no speaker . 1st question is what sort of HT voltage and/or anode current should I aim for?

Thanks. I may need to make a variable PSU, don't have one that goes high. O r I could just go up in steps with what I've got - that sounds quicker.

NT

Reply to
tabbypurr

Just put a few poundland PP3s in series.

Reply to
Geo

'Ideal' B+ voltage is determined by the specific tube installed.

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

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