Repairing Bosch red trumpet horns

[Jrsully]

Anybody have a quick fix/repair to check stuck Bosch Red Trumpet horns (off my 71).? Car was sitting for over 10 years and I hooked the leads from a Battery Tender and nothing, no sound at all. Supposedly there may be contact points that may be surface rusted shut.? Any help appreciated

[Gearby]

You might change the title to repairing Bosch banjo horns. Banjo horns are what you have there. I've messed around with the internals on banjos but couldn't get them to work. Clyde Boyer may have a few tricks up his sleeve. You might get a hold of him.

[Haasman]

Go to eBay and find matching modern versions. Cannibalize the new one's and put on the old horn section. Make sure you have the correct pitch (high and low)

[Jrsully]

Went to Ebay, couldn't find anything close.? These are in pretty nice shape, probably just need to be taken apart, cleaned, sanded in areas and put back together. Have never done horns, but I'm sure somebody has.

[SIMI BOB]

I would guess that a battery tender doesn't have enough amps (15 to 20?) to sound the horn. Try hooking it to a battery.
Pretty easy to see how that thing works. When you apply 12V, it activates the coil in the bottom picture, turning it into a magnet. That draws the flat steel bar in the top picture to it, which flexes the round metal disc connected to it. When the bar is drawn into the magnet, the small tab sticking out of the side by the Phillips screw contacts the brown (non metallic) tab on the right of picture two (switch), disconnecting the 12V circuit and the disc pulls the flat bar back up, which energizes the coil again, and so on, causing the disc to vibrate and make noise. Take that switch apart and make sure that the contacts in that switch are in good shape (if the horn has seen some use, the contacts could be burnt up), and file flat if possible. If you do file the contacts, be aware that you are changing the geometry in the switch, and you may have to make some adjustments to make sure that when the magnet pulls the bar to it, it opens the contacts to shut off the magnet. This adjustment will probably alter the sound of the horn (how far the disc travels), and you may have to try a few different settings until you get the sound you want.
And make sure when you screw it back together again that the tab near the Phillips screw is above the brown part of the switch.
Bob B

[Gearby]

Go to eBay and find matching modern versions. Cannibalize the new one's and put on the old horn section. Make sure you have the correct pitch (high and low)

That only works with red trumpets. These are red banjos and I've never seen any replacement internal components for them. I wish somebody would make them.

[t6dpilot]

By the looks of it, that should work to some degree. Simi Bob explains the process well. I think that a lot of the time the coil burns up and causes the horns to not work. That is what has happened to my three horns. Trying to find a source to rewind the coils using the existing bobbins and then reinstall. That is proving challenging. In your case, it appears that the coil is in good shape and the condition of the E I laminations appear good (no corrosion). If you apply 12VDC to the horn, it should magnetize that E laminations and at least pull in the I bar. Or try applying the voltage and see if the E laminations are magnetized by putting a small piece of metal (iron) on it.

[chiroracer]

I have usually taken them apart and cleaned them and they mysteriously work again.