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A Model 16X story
OK, on to the speaker.

The poor cone - which had been patched up in our early 2000's work had now deteriorated to a very poor state:


I found some suitable card on-line, and worked out the maths needed to make a new cone, using the voicecoil and center section of the original, which were still in good condition.


The surround was made from six pieces of cotton cloth. This was "doped" with shellac to stiffen and flatten it, and an original used to make a template. They were cut and stuck to the perimeter of the cone. 

Holes were punched in the surround, and everything reassembled.


New wires were made up. The original wire was braided (presumably for flexibility). I approximated this with (if I recall correctly) 16 strands of #36 wire twisted together, and pulled through the cloth insulation stripped from some of the wire on hand for the project.

I was please to find everything went back together, and the cone centered nicely. With a 9V battery on the field coil, I fed some audio from a small portable radio. Success - nice clean sound!
nice work!!
Icon_thumbup Icon_thumbup
What kind of paper have you used for the cone? Is it a suitable one?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
What I used was art card stock matched for thickness and weight - it wont be perfect, of course. However, I reasoned that it is very hard to match what was used originally, especially where one has to make a judgement from the 80+ year old material of the old cone. Even in good condition for its age, an old speaker may not sound like it did when leaving the factory - what I was presented with was so fragile it would barely hold itself together.

From the limited testing done (I could take this further and mount the speaker in the cabinet for the full effect) I considered the sound/tone to be very acceptable. Proof of the pudding will be feeding it from the 42 P-P output stage with honest to goodness AM radio.
Ed, it will surely sound. I think it will sound more akin to those large table speakers with cones made out of cardboard.
A 16 speaker if the cone survives, as well as all the old speakers that have their cones intact (amongst those are the 37-116 speaker that sounds just spectacular), that I encountered, sound great. A 16 is a great radio with a very good output and it will sound like that cardboard speaker whereas it could sound really bright.
I re-coned my 16 in a pro shop with a todays cone, but if you are bent on doing it yourself, my advice would be, use an actual cone - they do exit in proper size today.
If we were talking about a 1920-something radio, sure, but 16 is considered the best tabletop radio for a reason, and when put in a console cabinet with a larger speaker, it is a superb performer.

You did a great geometrical job, but sorry to say, geometry alone won't do it.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
If you don't mind my asking, where would I go about finding a cone? I did some searching but aside from modern kits, could not find anything.

If (hopefully when) I get this thing going, it might be something to revisit. However, one thing I had wanted to preserve was the method of construction. If we get as far as a working radio, and BBC World Service sounds wrong, I'll take it from there Icon_biggrin

This might not be the one you need, but there are others. Also, there are modern cones (one of those was used in re-coning of my 16's 8" speaker) that are as good or better. As long as you do not use "compression" speaker parts: if you go to a pro who restores old speakers, they know what to use and what no to use.

You could ask around here: some folks have cones.
You could possibly find a pro speaker shop and ask them for a cone (if you want to do the repair yourself).

This said, one thing at a time is the way to go, and if your speaker actually works, I would first restore the rest and then address this.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
The original Philco U-2 speaker is 10-1/2 inches in diameter. The eBay cone would be too large, plus the voice coil appears to be 1 inch - too small. And then there's the problem of it having an external spider rather than internal (within the voice coil).

The eBay cone is likely for a 1939-42 (and possibly newer) 12 inch speaker.
Ron Ramirez
Ferdinand, IN
Я этого не понимаю
There's a U-2 speaker on ebay right now. At $100 +$62 shipping, I shall be giving my repair every chance to prove satisfactory  Icon_biggrin

Anyway, this brings things more-or-less up to date on the restoration activities of the last year. The cabinet is also looking nice, although there are still some trim pieces to glue, and replacement grille cloth needed. 

In summary, work done so far includes:

Clean up of chassis
Replacement of frayed wiring
Rewind of interstage transformer
Rewind & repair of shadow meter
Repair of speaker
Replacement of all paper and electrolytic caps
Recap of tone control
Replaced volume control/switch

Remaining tasks include: 

Rewind of output transformer - almost complete, just the 60 turn secondary to do.
Replace speaker/HT connecting cord wires
Complete assembly and sundry wiring e.g. shadow meter, dial bulbs etc.

..And then we'll be on to bench testing. I've tested a few benches, so we should be OK there  Icon_crazy
It's too bad I didn't know you needed a U-2 a couple years ago. I took several speakers, including one or two U-2s, to Kutztown and gave them away for Phorum donations. Icon_sad I had too much clutter here (still do) and wanted to start shrinking the stash of stuff down.

But it looks like you did a great job of DIY reconing! Icon_thumbup
Ron Ramirez
Ferdinand, IN
Я этого не понимаю
Thanks Ron, I really think this is worth a try. Plus it adds to the fun.
Funny thing was, after completing the interstage wind... one appeared on ebay and I bought it anyway as backup. Not expensive at all.

The hardest thing to find - time to work on the radios, and I managed to get sidetracked by at least one more modern receiver in the middle of all this...can't help myself!
Your speaker may sound surprisingly good. I agree, give it a try before buying another.

M R Radios   C M Tubes
+1 with the DIY speaker cone. I've had pretty fair success with repairs of that nature, with good sound. Hope it works for you!
Not much progress this weekend - I was tasked with other things by the domestic authorities. Thankfully the chicken coop is now repaired and on level ground...

I did take a look at the next stage of the O/P transformer wind, and decided I didn't like any of the paper I had available to go between the primary and secondary, so ordered some 5 mil "fish paper". This stuff will be nice and hard, protecting the fine wire and providing a good insulator between the 400V HT on the primary and the output winding. I then cut a small length of 18 a.w.g. wire for practice, to see how it behaves when winding using a dummy core. Hand wind looks to be better than the machine for this large gauge. The technique for securing the start, and handling of the wire - which seems soft annealed - looks to be no problem, so I'll crack on with it once the paper arrives.


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