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lucas altette horn - contacts problem

airhead

Forum Website User
Non-VOC Member
the photos show my 1951? altette horn, alette horn 001.jpgalette horn 002.jpg
it has stopped working,
stripping it down, the coil is good with resistance of 0.4ohms ,
but the resistance across the contacts is open circuit rather than the"0" ohms i expected.
the contact gap is "nothing"...a couple of thou??
there does not seem to be any adjustment on the contacts...
so help....
has anybody got any advice as to how the contacts can be adjusted
many thanks
 

stumpy lord

Well Known and Active Forum Website User
VOC Member
I believe that for your model of horn , the adjuster is underneath the large dome nut, which is situated in the centre of the front of the horn.
stumpy lord
the photos show my 1951? altette horn,View attachment 2149View attachment 2150
it has stopped working,
stripping it down, the coil is good with resistance of 0.4ohms ,
but the resistance across the contacts is open circuit rather than the"0" ohms i expected.
the contact gap is "nothing"...a couple of thou??
there does not seem to be any adjustment on the contacts...
so help....
has anybody got any advice as to how the contacts can be adjusted
many thanks
 

greg brillus

Well Known and Active Forum Website User
VOC Member
Points should be closed, as John said.....perhaps the adjuster screw has been wound in too far and bent the points spring.....clean points with a piece of doubled over emery tape and blow clean with compressed air or pass through a piece of cardboard, and all should be well..........Cheers.......Greg.
 

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
You need to be sure you've still got the contacts! I have known them to be melted off after excessive current or heat. You have one of the less adjustable models. Use paper gaskets under the diaphragm to achieve about .012" clearance between the magnet body and the armature, this is a bugger to check but it can be done. Then assemble. You may need to make up a gapped screwdriver to loosen the adjustment nut under the chrome nut. Make sure the points can close, and are clean as previously suggested. You should lubricate the fine adjustment threads with a bit of WD40 or similar. You may be able to feel the contact of the little plunger on the leaf spring. Back off 1/4 turn from contact then adjust for 5.5 to 6.5 amps consumption and a good tone.Best not to run 12 volts through a 6 volt horn, better to get a 12 volt one from an old car and transpose the shiny bits. You can use right-angled circlip pliers to do the locknut in an emergency.
 

airhead

Forum Website User
Non-VOC Member
Hi Guys,
thanks for all the feedback and advice,
the points(contacts) are good ...solid but clearly not quite touching as they are not making an electrical cicuit even though to the naked eye they look to be "touching".
the bottom "spring" contact can't be bent up as the couple of thou gap before it hits the top contact isn't enough,
hence the problem : (
i can only think of drilling the top of the rivet heads off ,to bend the bottom spring contact,
and then on reassembley drilling and taping the rivet to take a small pan head screw?
 

nkt267

Well Known and Active Forum Website User
VOC Member
Could you bend the top contact down?.It's a long time since I looked inside one..John
 

airhead

Forum Website User
Non-VOC Member
Hi Guys,
some progress,...after a prolonged play.....nothing on 100 tv channels ,
i've got a low resistance circuit through the points,
so i'll put it back together and post the readings if it works ,
many thanks for all your advice
 
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