Author Topic: horn problems  (Read 3490 times)

Offline flashblack

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horn problems
« on: 08.03. 2009 16:14 »
Can anyone advise on getting a better tone from my altette horn?
I`ve cleaned the points etc inside, and then turned the adjuster screw to get the best tone which is not loud enough to be heard when the engine is running!
There is continuity across the horn terminals and the wiring and button is all good.
  Is it easily fixed or do i look for another horn? Any thoughts would be appreciated.
                                         cheers
                                                Richie


     p.s. these pics may be of help.
 
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Online trevinoz

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Re: horn problems
« Reply #1 on: 09.03. 2009 00:05 »
This is a very fiddly job.
First, mount the horn on a bracket in a vice. After assembly, of course, with the dome nut removed
Loosen the large nut on the back. Loosen the lock ring in the centre of the armature and back off the adjusting screw.
Apply 6 volts to the terminals , from a BATTERY only. Ensure the diaphragm is moving and the points are not opening. This is seen by the diaphragm staying in. Don't hold for more than a couple of seconds as you can burn out the coil.
Adjust the rear screw until you hear a distinct click as the armature hits the pole. Lock the nut and retry, it can change.
If you have a dial gauge, measure the movement of the armature, it is supposed to be 11-13 thou. The horn will work OK with slightly less.
Next adjust the centre screw in the armature until the horn sounds OK. Lock the ring and fit the tone disc and dome nut.
Fine tune with the adjusting screw on the back.
The Altettes without the adjusting facilities, from 1949 - 52 are very difficult to tune. It is done by adding or subtracting gaskets from beneath the diaphragm to get the measurements above.
Don't use a battery charger or any rectified DC to test the horn as it will not sound right. Use a fully charged battery.
I hope this long winded answer helps. I have overhauled countless numbers of these horns.
  Trev.

Offline flashblack

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Re: horn problems
« Reply #2 on: 09.03. 2009 17:47 »
Thanks Trev thats excellent, i`ll let you know how i get on
                                           cheers,
                                               Richie
build it, ride it, live it!

Offline shabashow

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Re: horn problems
« Reply #3 on: 09.03. 2009 20:03 »
I bought a new one at a high price for my rebuild - it looked lovely, but I couldn't get a decent or loud enough sound out of it.
Now it is for show and I have a £2 horn hidden away under the seat - plenty loud
John

Offline flashblack

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Re: horn problems
« Reply #4 on: 10.03. 2009 20:42 »
Trev
       I followed your instructions and now the horn works great! Interestingly, there was a lot more armat
re movement than 11-13 thou, but despite that the horn is louder than it`s ever been.
             Thanks again, that was greatly appreciated.

John
       I was thinking of doing exactly what you`ve done if i couldn`t fix mine, in fact, i`ve even thought about putting one inside an altette body, i don`t know if you could fit one in or if anyone`s tried?
                                cheers
                                          Richie
build it, ride it, live it!

Online trevinoz

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Re: horn problems
« Reply #5 on: 10.03. 2009 21:39 »
Richie, you adjust the armature movement via the screw on the rear, the large one with the locknut. You can adjust by "ear" until you get the best sound after you ensure that the armature is hitting the pole.
With a digital ohm meter, the horn resistance is very low, typically 0.4 - 0.6 ohms. I have found dirty points to be the main cause of horns not performing well. [and "experts" fiddling].
There are lots of 12 volt horns getting about which do not work satisfactorily on 6 volts. If in doubt of rated voltage, the resistance of the 12 volt type is over 1 ohm. That is unless the points are dirty which makes life difficult if the horn is not in pieces.
I have rewound many to 6 volts.
I have seen bodies butchered to fit a small horn inside, but that goes against the grain as it is a challenge to get the original set up working.
I am just guessing, but I think the distance of armature movement governs the frequency of output sound.
  Trev.

Offline flashblack

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Re: horn problems
« Reply #6 on: 11.03. 2009 17:29 »
Trev, well i misunderstood your instructions last time so now i`m going to have another go and this time adjust the armature movement with the screw at the back instead of just turning it until i heard an audible click (which is what i did last time). Hopefully i should now get an even louder noise from it, although it scared the life out of next doors cat as it was!
                                              I`ll keep you posted,
                                                          Richie               
build it, ride it, live it!

Offline flashblack

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Re: horn problems
« Reply #7 on: 11.03. 2009 20:34 »
Right- horn adjustment part 2,
                       Have achieved minimal movement of the armature ( unfortunately i don`t have a DTI so i`ve had to do it by eye and trial and error until the best tone was achieved. Ultimately i`ve ended up with an even louder sound than before, but the biggest improvement is in the pitch which is now higher and gives the note a much sharper sound, in fact it`s now as good as any 6 volt horn i`ve heard.
    I very nearly gave up on that horn, but having the right information has achieved a very satisfying result.
                      My hat`s off to you Trev,
                                            cheers,
                                                     Richie     
build it, ride it, live it!

Offline shabashow

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Re: horn problems
« Reply #8 on: 12.03. 2009 20:13 »

John
       I was thinking of doing exactly what you`ve done if i couldn`t fix mine, in fact, i`ve even thought about putting one inside an altette body, i don`t know if you could fit one in or if anyone`s tried?
                                cheers
                                          Richie
[/quote]

I haven't seen one fitted, but have seen somewhere on the net exactly that proposal, so it is possible. Might have been Paul Goffy's site, but not sure,
John