[MrFixr55]

No easy solution like the coil connection being broken right at that green lead-in wire? Saved a headphone that way. Once! you may even get to the connection at the "inner connection (the start of the coil) I would unwind a layer at a time for a couple of layers before giving up.

Good luck. This driver looks nicely instructed.

[klondike98]

Back at this Thompson speaker. I decided to work at making it look presentable first since that's the primary interest of the museum and then satisfy my own interest in getting it working second. As seen in earlier photos the base is very rusty so it spent a day in Evaporust. Dremel tool grinding got the rivits off of the label and then I stripped the old paint off. Some primer and gloss black and its starting to look better. I"ve added a shot of what it looked like when it first came into the museum (we were later able to find the missing horn pieces). I think I may be able to do some more touch up on where the broken pieces were glued back together but that's for another day.

[Image: https://www.dropbox.com/scl/fi/uw4p7qveg...m0yv&raw=1]
[Image: https://www.dropbox.com/scl/fi/d8najtz40...83hm&raw=1]
[Image: https://www.dropbox.com/scl/fi/sbt1lzngc...q11j&raw=1]
[Image: https://www.dropbox.com/scl/fi/q4rpzz3oy...f4sa&raw=1]
[Image: https://www.dropbox.com/scl/fi/7luflzv5j...bv9s&raw=1]
[Image: https://www.dropbox.com/scl/fi/s95nimoxz...tgfe&raw=1]


I was able to get the coils off and unravel the first one. I took off an entire layer of wire and then came across several places where the wire had broken. It now is showing 900+ ohms so I think the rest is OK (don't know how long it will last but we'll see). The second coil comes off the next time I'm in the shop and we'll see if I can find an early break. If not I'll be ordering some glassine paper, insulating varnish and give rewinding it a try

[Image: https://www.dropbox.com/scl/fi/jj6gjhz9y...jd5z&raw=1]

[MrFixr55]

Bob, really nice job on the base! Give a pic when you get the horn done. If you get 900Ohm on the other coil, I think you are good enough. I think that most of those horn speakers (and even the magnetic cone ones) were about 2K Ohm. Did you ever find more info on that little 1 tube radio in the art deco cardboard case?

Took a look at the earlier disassembly pix of the Thompson speaker. Interesting construction, as it appears that the diaphragm is not metal? I guess that the metal reed moves the diaphragm. Would be neat to compare the sound of this speaker to one with a metal diaphragm. Bet this one sounds better!

[klondike98]

Thank you. Yes I only lost about a foot or two of the 40 gauge magnet wire on the coil so I'm still pretty close to what was originally there. Fingers crossed for the other coil. I agree I think the diaphagm is something other than metal. I'll take a closer look next time I'm in the shop and yes the metal reed is connected to the diaphragm and is what the magnetic field from the coils acts upon.

As for the one tube radio. I was able to locate one reference to it on the radiomuseum site which seemed to confirm the Century of Progress Worlds Fair connection that you initially identified. See: https://philcoradio.com/phorum/showthrea...#pid193628

[Chas]

From the one pix posted, the diaphragm of the Thomson speaker appears to be "Micarta". Though the term belongs to George Westinghouse, it is phenolic resin molded with linen cloth. This material can still be bought in sheets for electrical purposes. In the speaker, the diaphragm is custom molded. Micarta is a thermosetting "plastic" resin.
https://en.wikipedia.org/wiki/Micarta

Yes, I do agree it should sound far better than a metal diaphragm, probably akin to a Thorola which has a large mica diaphragm. Epoxy or Gorilla glue can be used to repair.

If you have access to an "old school" magneto repair shop, magnetos are on older tractors, they will have a magnet charger. Generally for a couple of bucks they can re-charge the magnet.

Chas

[klondike98]

Thanks Chas. I think you are correct, though I did not know what to call the diaphragm material. The horseshoe magnet is still relatively strong so I will give it a try before going the recharge route. I was able to get the second coil undone and had a similar experience to the first coil. I unwound about two feet of magnet wire, with about 3 breaks in roughly the same spot on the coil and then got continuity. Added in a new lead wire, reapplied the outer protective covering and also added one wrap of black electrical tape to hold it all together. Had to bridge the connection between the two coils but now I'm seeing 1821 ohms for both coils. I'll put it all back together next time, hook up to the Crosley Trirdyne and see what we have and if it survives when voltage is applied.
[Image: https://www.dropbox.com/scl/fi/lw6ajaudj...d1sg&raw=1]

I also did a little more paint touch up to the horn where the pieces were glued back together. It will never look like new but this is about as good as I can do for it. I could repaint the entire horn and that might make it look better but I think this is the way I'll leave it. I did clean the horn with a mild detergent and then put on a paste wax to give it a little shine.
[Image: https://www.dropbox.com/scl/fi/ei1muybb0...lmd9&raw=1]

[Chas]

Bob,

That looks very nice
IMHO the loss of turns seems very minimal. I think it will play fine...

Chas

[klondike98]

I put the Thompson speaker back together and hooked it up to the Crosley Trirdyne that I worked on and.....nothing

I do get a pretty good clicking when I put a 1.5v battery across the speaker leads so to be honest I think the speaker is working and it may be the final stage of the Crosley that isn't. I was able to get good reception when listening with headphones but that cuts off the final stage of the radio. After some careful tuning and increasing the volume as much as possible on both the radio and the speaker adjust I was able to hear the very faintest bit of music in the speaker. I think I need to go back into the Crosley and see what's going on. Look for a new post in that thread...

[MrFixr55]

Hi Bob,

Try the phones on the final of the TriDyne. If they don't work, that confirms an issue with the final. Likely that the secondary of the coupling transformer is bad or a switch contact on one of the jacks is dirty.

The thing looks beautiful. If you want to "guild the lily" and there is no pattern embossed in the horn, you can smear some NitroStan over where you glued, sand down and repaint. Put on a little at a time and let it dry between coats. Sand, prime and paint.

[klondike98]

Thank you all for the assist on this project! I got the Crosley Trirdyne working and confirmed that the Thompson speaker is also working! If you would like to hear it in action click the link below:

[Video: https://youtu.be/59QSypuYYL4]

[Chas]

Well done Bob!



Chas

[EdHolland]

Nice work, and it is really interesting to see some of these early systems, and what makes them tick.