Crosely Trirdyn Regular 3R3 1924 Regenerative AM Radio

[TelePlay]

Another radio I saw sitting on the top shelf of an antique store for at least 6 months. No one wanted it so I did my research of what it was and bought it. They were asking $95 but got it for 10% off just for asking for the "just before closing" discount. So, it cost me $84.76.

It has 3 tubes and the cheapest I could find as replacements were $20 each, some wanted $39 each. A very old tube dating to 1924, when the radio was built. The wood cabinet is is fine condition and the inside components are clean and working smoothly. Quite the radio.

Don't have pictures yet so am posting stock photos to show what I now have. Sold for $65 in 1924.

[TelePlay]

How it works.

[LarryInMichigan]

You will need a power supply and speaker for this radio.  There are some very active collectors of these types of radios on the antiqueradios.com forums.

Larry

[TelePlay]

You will need a power supply and speaker for this radio.  There are some very active collectors of these types of radios on the antiqueradios.com forums.

Larry

Yes, from what I've read so far, it's a 3 battery (A, B & C) receiver: 1) 90VDC, 22.5 VDC and 4.5 VDC. I found somewhere it has to be a high impedance speaker. The one someone used on the radio forum said it was 1000 ohm impedance. I guess my crystal radio headphones would work, and there is a 1/4" jack for headphones on the front right.

It would be nice to power it up, see if it runs and sell it. The inside wiring looks like they used coat hanger gauge wire to make all of the connections, really heavy stuff.

[unbeldi]

You will need a power supply and speaker for this radio.  There are some very active collectors of these types of radios on the antiqueradios.com forums.

Larry

Yes, from what I've read so far, it's a 3 battery (A, B & C) receiver: 1) 90VDC, 22.5 VDC and 4.5 VDC. I found somewhere it has to be a high impedance speaker. The one someone used on the radio forum said it was 1000 ohm impedance. I guess my crystal radio headphones would work, and there is a 1/4" jack for headphones on the front right.

It would be nice to power it up, see if it runs and sell it. The inside wiring looks like they used coat hanger gauge wire to make all of the connections, really heavy stuff.

Yes, the circuit diagram you showed tells you that you need a high-impedance speaker if you want to use the second, last amplifier stage.   The speaker functions as the load impedance directly in the anode circuit of that final stage, a simple triode using the highest voltage probably as its work function.
However, it seems to me you can also use headphone by not powering that last stage.  The stage is driven by a transformer and the output of that, or perhaps even the input, should be just fine to drive a headset at very low voltage.

PS: I can't quite make out what that "thing" is in the lower center but it looks like this may indeed be a head-phones jack.  Or some kind of switch?

[19and41]

That'll be fun to get going.  Hope the tubes are functional.  That is a headphone jack in the schematic.

[TelePlay]

PS: I can't quite make out what that "thing" is in the lower center but it looks like this may indeed be a head-phones jack.  Or some kind of switch?

This is the "Supreme" version, the wood cabinet has feet, otherwise the front panel is identical to the Regular, the one I have. It's funny that they labeled everything except the headphone jack on the lower right. The "thing" on the lower left is the filament switch. I will post close up pictures of the internals. That switch is something I've not seen before.

The second image shows the components in the schematic. The filament switch, unnumbered, is between 4 and 5.

The "feedback control" pulls in and out. All other controls turn, except the filament switch which also pulls in and out. A fascinating design just a couple of generations past the crystal radio era.

Needs and external antenna, a good ground, three battery sources (voltages) and an appropriate speaker.

Here's a video of one like mine in operation. Note that it can be turned into a transmitter by improper tuning.

https://youtu.be/vFWFVvhBiro

That video (which was created for an eBay listing in 2008) had the description "Demo of playing/tuning a 1924 regen Crosley model Trirdyn Regular radio. Using 3 01a tubes with 18v(B2), 45v(B1) and 4.5v(A)."

[Bill]

I found somewhere it has to be a high impedance speaker. The one someone used on the radio forum said it was 1000 ohm impedance. I guess my crystal radio headphones would work, and there is a 1/4" jack for headphones on the front right.

The original radio would have used a high impedance speaker - 1000 to 10,000 ohms or so - at the terminals labelled Output. The high-impedance speakers of the day had a voice-coil, which is a coil of hundreds to thousands of turns of fine copper wire. DC current could pass through this voice coil to the operate the final tube. However, crystal headphones will not pass DC, so they won't work at the Output terminals.

Today, the old high impedance speakers are no longer used, and originals are a bit expensive. A good work-around is to use a common low-impedance speaker with an "output transformer". Both are easily available, and in most collectors' junk boxes. Radio Shack has a small output transformer for $3, and a speaker out of any transistor or post-WWIIl tube radio will work.

The headphone jack would have expected high-impedance phones having DC continuity to be plugged into it. Like a high-impedance speaker, these phones would have contained a coil of thousands of turns of very fine wire. I think that DavePEI described such headphones in a recent post, though I can't find it at the moment.  So crystal phones probably won't work if plugged into the headphone jack.

In the absence of a high-impedance speaker or phones with DC continuity, Unbeldi's suggestion of using crystal headphones direct-connected after the second stage may work well.

I don't fully understand the function of the headphone jack. It contains a switch that appears to be part of the DC distribution,  but in a way I don't get. Of course I am not really good at regenerative circuits, so I will study it a bit more.

Bill

[unbeldi]

I took another look at the circuit and redrew it so that I can understand it better without much clutter of crossing traces.

I think from this the function of the head phone jack is clear. The built-in switch disconnects the audio signal after the regenerative stage from the input to the last loudspeaker stage and simply outputs it on the head phone jack.

A regenerative stage is basically a positive-feedback amplifier (modern term). The anode current in the second tube stage is sampled with a tickler coil (at the very top of the circuit) that is coupled with the input transformer T2 and therefore introduces amplified signal in-phase with the output of the first stage so that the tube recursively amplifies the signal, which is presented as  input to the final stage or to the head phone jack. But I believe the headphones have to be high impedance too, but this depends on the impedance of the primary of T2. In the end, it should probably have the same impedance as the primary of T4, which can be measured. Crystal sets won't work, I don't think.

All tubes operate on a negatively biased cathode, and the anodes are basically the ground potential of the circuit, but I suppose it could be seen the other way around too.  The power switch controls both the filament voltage (A) of all tubes, together with the negative potential of the B battery (90V).

Battery C provides the negative bias voltage for the gates of the triodes, modulated by the input transformer in each stage.

I think this diagram makes the operation a little clearer.

I didn't have a symbol for a triode without separate cathode, so I had to improvise with the filaments.

[TelePlay]

Thanks for doing that.

And, yes, you are correct in the headphone jack use. I found this paragraph this morning from the radio's manual published in 1924 or so.

And, by crystal headphones, I meant some of the 1,000 ohm electromagnetic headphones I collected for use with my Martian Special crystal radio but don't work well due to the low load. I would never put my one and only 2,500 ohm piezo crystal headphones on this circuit for fear of blowing the crystals.

The filament switch operation from the manual is also below.