[morzh]

I have 3 G speaker, all with open Field coils.

Today I pull one of the shelf and decided to try to remove the FC (spoiler: so far I have not succeeded).

Now, this speaker is very clean and has excellent cone (yeah, yeah, with the solid spider).
I bought it fr om a lady on eBay, and when I found out the FC (she said the speaker worked) was open, I told her and she was willing  to refund everything, but I told her that I would pay part of it as the transformer was good. I used it for something else.
The speaker has been on a shelf for more or less 8 to 10 years.

I remembered what a screwdriver can do to the spider when it slips. I was looking to buy a screwdriver with a spring-loaded guard shrowd, but have not found any. So today I did  this: I took the 7/16 socket from my Kraftsman kit, and used the heaviest screwdriver that could go through it.
   

I helped the socket to stay around the split washer; it did not require any effort: just so it did not slide. This kept the flat screwdriver from sliding sideways. Surprisingly, the screw did not resist too strongly, and I removed it without any damage to the cone or the spider.

Then came the turn of the big nut in the back, that holds the pole.
Luckily I bought 1" socket a year ago. I tried it with the standard Kraftsman driver, and it would not budge, plus my hand was hurting.
Then I remembered I bought a piece of steel pipe as a lever, when 3 years ago I was trying to rebuild my pool pump, and the bolts did not move. With this as a lever, they moved very soon. They were really calcified (I think I put the photos here then; it was, I think, May of 2022).
This is what the pipe is and how it is paired with anything (wrench or socket driver).
   
   

I used a thick large square-crossection screwdriver (same one I used on that capacitors can) to counter the effort. This is good steel and thick enough to not bend.
The screwdriver is inserted in the screw slot in the speaker base, and then pushed clock-wise when the nut is driven counter-clock-wise.
   
It was a good idea but it did not wor either. The nut wouldn't budge.

Then I decided to secure the speaker in my large vise.
   

I would have to be gentle with squeezing as the base looks to be something like cast iron, and could be brittle.
I had to adjust the vise 3 or 4 times as the speaker would get loosened up.
Eventually, I realized this was not working either, and decided it was time for PB Blaster.
Which is what I applied, and the liquid happily got absorbed, both in between teh screw and the nut, and between the nut and the base.
I am soaking it for now and will attempt the nut removal again later.

[MrFixr55]

Hi Morzh,

May be a good idea to remove the cone to prevent damage. You may have to do so anyway to remove the pole once you break the nut loose. I suppose that if it is like the RCA speakers, you remove all the screws at the perimeter of the "basket".

I usually keep a nice pipe around for the same purpose. I refer to it as a torque amplifier.

[Chas]

hen I remembered I bought a piece of steel pipe as a lever, when 3 years ago I was trying to rebuild my pool pump,

During my working career, I was a industrial hydraulic mechanic, short term: Pipefitter. Removing unions from 3" steam pipe that had been joined for some 40 years always a problem. The bashing with a 10# sledge the the application of the "Trimo" 4' pipe wench, didn't always succeed. So, a 6' section of pipe was applied to the Trimo, affectionately called a "gunner"... Always had to have a helper, the Trimo weighed in at 30# with the gunner something like 50#'s. Helper would support the assembly and I would jump on the gunner...

Most of the early speakers were glued with celluliod cement, it will soften and release with repeated application of acetone. Then the cone, spider and voice coil can be removed as an assembly.

GL

Chas

[Arran]

Mike;
I believe that the cone on this "G" type speaker (same as the one in a model 96) comes out like the ones used in RCA and G.E sets, as was mentioned. I second the suggestion that you may want to remove it before going further, at the very least It might allow more purchase on the basket whilst you are trying to undo the nut on the back of the pole piece. Yes, soaking the threads is a good plan, it has been together for 90 years, does anyone also know whether the threads are right handed or are they left handed like on a circular saw?
Regards
Arran

[morzh]

Yep, I need to remove the cone.
Watched some videos. Folks do it with razor blades.
I wonder if acetone/lacquer thinner is a better option.

[Arran]

Mike;
Yes, I would try acetone/lacquer thinner is the cone won't budge easily after the ring is unscrewed, such as with a putty knife, this is how I've removed cones from more modern speakers that were glued onto the basket.
Regards
Arran

[morzh]

...and this is what I did. I fed a little LT into the screwholes with a small brush, and a little on the rim next to the same holes, and the Exacto did the rest.
Surprisingly, not much damage at all.
However when I applied LT to the pole, to lift the spider, the latter left the piece of it (and I was not rough at all) on the pole. I saved it.

This is the washer on top of the spider.
   

The piece of spider stuck to the pole. I mean the black piece in the center, not the actual spider in the gap.
   

After it is removed:
   

The basket. You could see a little piece of the cone stuck to a hole.
   

Then off the basket went back to the vise, and after a while, when I realized I need to stick the rim under my armpit (it did not complain) to counter the down force which rotated it in thr vise, the nut gave up.

The pole
   

The coil
   


Now what do I do? I doubt I will rewind the coil myself.
It is a pound and a half of copper.

[Arran]

Mike;
 I would unwrap the field coil, and see if maybe there a break near one of the ends, like where the coil wire attaches to the leads, if it does not look like the winding burned out it's either corrosion, or a mechanical break in the wire. Bob Anderson had a go at repairing a pie pan speaker for a Philco 70 or 90 (same speaker used in each I think) and he only had to rewind part of the coil to make it work again. 
Regards
Arran

[morzh]

Arran

Yes, this is my plan for now and what do I got to lose, this is not even the speaker from this radio, but one of three G ones with open FC I have. Might as well.
But I thought to pick the brains around here, for what if someone has a better idea? Like, Mike, now that you achieve this measure of success, discard the whole darn thing and try to get a new speaker.


Yep. Tomorrow.

[Arran]

Mike;
I've only run into a speaker with an open filed coil twice, and they were on newer speakers from the 1940s. One was in an Addison radio where some dummy drove a screw into the coil, or ran a drill into it followed by the screw, so it likely had two dozen or more breaks in multiple turns, the other was in a Serenader radio, made by Electrohome, where the output filter cap had shorted burning the thing out. All of my other inductor problems in the audio output stage were open primaries on output transformers, or on audio interstage transformers, the latter seem to fail almost as often as filter caps.
I noticed something interesting, the top end of the pole piece has a pair of holes machined into it like they used a spanner on some sort to hold it whilst they cinched down the nut at the other end. I'm not sure hole large the holes are but I think a spanner from an angle grinder might fit, the type made out of thick wire, and that are sort of springy.
Regards
Arran

[MrFixr55]

Was that pole piece left handed ?

Since the metal "spider" is toast, wonder if you can either get the "45 Adaptor" type, or the modern type. Big difference in the sound. I had the opportunity to "A-B-C" compare 2 model 20 pie plate speakers, one with the metal no-give spider and one with the "45 Adaptor" spider with a modern 8" PM speaker, using the same chassis. The 45 Adaptor spider" unit sounded soooo much better than the metal spider and almost as good as the 8" Taiwan job.

[morzh]

MrFixr

Yes, it is my plan to go with 45rpm spider if I go that far.
No, the pole was not left-handed as I unscrewed the nut the regular way.


Arran

Open FC is extremely popular with old FC Philco speakers: K and G.
I have two of K and 3 of G (and those are I got with radios) that are bad.
Thos Ks I bought as spealers are good, but of course I wouldn't buy them otherwise.
The two bad K speakers both are from 70 radios, one from the 570 tower clock and one is in my last console, that I am yet to take on. And of course the poles are pressed in.

[morzh]

Well....here it is.

The green stuff. Unfortunately, probably penetrates deep.
I opened the top layer and saw that:

The first wire was OK
   

But then the second wire showd this: Yikes!
   

So I started peeling the layers.
   
   

And as I  kept unwrapping, the wires were broken around the green:

   

So.
I doubt I should try unwinding the coil to see where the green stops. I am sure it will be a few millimeters deep at least.

I measured the coilm so I could do two things:

1. Order the new coil, new spider and reuse the cone.
2. Same thing, only with a new modern cone.
3. Screw it, use a PM speaker and a big a** resistor or a bigger a** choke.

[GarySP]

Mike, what ever happened to that plan you had to try using a rare earth magnet to magnetize the pole? This looks like a possible test subject here. Take care and BE HEALTHY! Gary

[morzh]

Gary

I in fact did, on a 38-14, I think, where I had a speaker with the dead coil.
Well...it kinda worked. Kinda, because it is not loud. When it should be, I mean.
Amd then...I do need the coil or a big 3kOhm resistor. Because this would be then a PM speaker.
This thing is heavy. Like under 2lbs. This much copper wire (AWG33) sells for $60 or so.