11 hours ago, grannyknot said:

Steve, I've done the continuity test, 1.6 ohms between the positive tab and the far side of the contact.

The only thing I haven't done is install the thin paper gaskets.

Great question, sir. What's happening at this point is that the bar on the diaphragm is not opening the contacts. Before you disassemble, connect your ohmmeter to the horn and tighten the volume screw slowly until the resistance goes up. Then back it down some. Test again and see if the bar can open the contacts.

Horns are working great now, thanks.

 

1 hour ago, grannyknot said:

Horns are working great now, thanks.

 

Those are beautiful sounds.

I used Steve's info to rebuild mine with the eBay kit from the guy in Canada.  I don't like those sticky gaskets.  The green is off, but it's what I had.  Individually they sound okay, but I need to hook the pair up together and fine tune, and drive my neighbors nuts.

After refinishing some horn pieces, to 6 horns, it came time to assemble them.  I did document and measure each piece and photograph the pieces, but what I didn't take into account was, you can't see thicknesses of washers from a photo.  And what makes a horn high tone, what makes it low tone.  Frustrated, I could only get 3 of my 7 horns working, I decided to dive into this deeper.  All the horns I could not get working, had good continuity.  So I Figured it had to do with the different thicknesses of washers and shims on each side of the diaphragm.  Their placement,  I thought, could also have something to do with the high and low tone.  So I sourced more horns through Junkyard Jenny, and hopefully they haven't been messed with.  If you ever need parts, she's great.

I get a variety of horns a few days later, and now I'm a bit more careful disassembling them.  Great care is taken to document and measure each piece of the diaphragm assembly as it comes apart.  Here are my results.  By the way, she called these her unruly horns as many did not work.  First off was to check continuity.   I found it best to clean the backside before disassembly,  by giving it a quick shot in the bead blast cabinet.   Next was to check continuity between the electrical connector tab and the rivet taking the current inside the horn.  That is where the biggest problem was.  I found that rotating the tab back and forth slightly would crush the corrosion.  I also put a few drops of wd40 rust dissolver on that rivet, and worked the corner of a razor blade around the corrosion.   The connection was fixed.

After sanding the contact points, the electrical was good.

It helps to have a chuck to hold the diaphragm shaft while removing or tightening the nut.  The earlier horns have a round spacer instead of a rectangular bar in the diaphragm.   The rectangular bar has to be aligned with the center or the alignment hole.  The latest horns I found with the round spacer were 6/71 or U6.  The U7 or 7/71 horns had the rectangular bar.

Here is the diaphragm orientation of horn T10, 10/70  

Here is T11, 11/70

I had a matching pair of B3 horns 3/78, one with a low tone L on the bracket.  I thought we might be able to tell what the differences are between it and the high tone:

The differences are clear, one has thin shims under the diaphragm,  one had a smaller rectangular spacer, not thinner, but shorter.

Horn W1, 1/74 had some changes.

A brass tab for the electrical connector,  didn't stop corrosion on the rivet though, and 2 slots in the cover.  This may have had the base changed to an earlier style so fwiw, here's the breakdown on this horn:

Here's U10, 10/72.  This horn actually faintly worked, believe it or nor.  Haha, I have it soaking in rust dissolved, but most likely it's a parts horn.

 

1 last horn U7, 7/71:

Looks untouched by how the thin paper gaskets were intact.