Found a neat horn today!

[Jpressman8]

Can you see if there is any cracks in the diaphragm? Make sure all of the screws are tight as well. As Pete said check the gasket and make sure the body halves are not vibrating against one another.

[Daniel]

Is the diaphragm hitting square on the aperture of the trumpet or is it bent?

Mine plays a moderately in-tune Eb. I actually wrote a musical piece in college that climaxed with the honking of the alarm. It didn't get a great grade, but it put the entire music department on the floor laughing!!

I would like to see a video of this! Here is a similar idea, though horribly tuned.

http://www.youtube.com/watch?v=BuEZemxHWaM

[Blasty]

The housing gasket is good. I can feel air coming out around the conduit hole where the wire passes in; should that be sealed, or does it matter?

I have yet to take the diaphragm off to look at it. As for the projector, I had to use a wrench on the nut to loosen it the first time. Therefore, I don't think it has been handled much, if at all, during the horn's lifetime. Nothing looks bent, but then I can't tell for sure.

I'll continue to mess around with it more and see what happens.

edit: by the way, the first video was before I ever opened the case or took the projector off, so I didn't mess it up before I tried it.

[Blasty]

I just played with it some more. There was a flake of metal stuck to the end of the horn, which I simply removed with a fingernail. I also gently buffed the end to a shine with a polishing compound just to make sure it would make full contact with the diaphragm. It appears from slight wear marks that the horn is fully contacting the washer that's bolted to the diaphragm when it's screwed down until it just touches. I have also run back through the contact adjustments each time I change something else.

Also, I've been doing tests with the case open, so I can make adjustments. Does the case need to be sealed up for it to work? And, should there be some kind of gasket at the threaded end of the projector, or should it contact the diaphragm directly?

After all this, still no progress. I'm about ready to give up on it, and in a few days I'll to be moving to a place where I can't constantly test it while I'm trying things.

[Pete]

- The case definitely needs to be sealed for it to work right...it will make all of the difference in the world!

- No gasket at screw-in point of projector/horn, though it doesn't seem right that the washer should be rubbing up against it. The horn doesn't have to be solid tight, if loosening it up a little will help the sound.

- conduit hole being open should be ok...mine isn't hugely tight and it still makes a good amount of noise!

Seal up the case (tightly) and try 'er again...let us know if it works now!

[Blasty]

Sorry to bump an ancient thread, but for anyone who wants their Federal 55 to HOOOOONK and not Bzzzzzz, I have finally figured this out. I hope someone else can find it useful!

Six years later...

I pulled this sad piece of junk off the shelf in my garage (oh yeah, I have a garage again so I can play with these things), and decided to replace the capacitor inside just for laughs. I'd already tried everything else, so why not. I thought its only purpose was as a transient suppressor of sorts to extend the life of the switching contacts... How wrong I was.

The original cap is .25µF, 1000V. I don't have one on hand, so I grabbed a .33uF 275V cap rated for across-the-line service. After soldering it in temporarily, I braced myself and ever-so-lightly touched the plug to the outlet contacts.

:O :O :O OH! So THAT'S what it's supposed to do! I gave it just a short blast in the garage, and it was just a little bit loud. I guess the cap was bad.

Now off to Surplus Gizmos tomorrow to locate a capacitor with a higher voltage rating. 275V might be fine, but I expect some nasty spikes from the inductive reactance of the coil, so I'd feel better if there was a greater safety margin.

So yeah, this case is closed.