I am going to try and get the horns working on a couple of my Postwar Alcos. What is the purpose of this little, "set screw", on the bottom of the horn unit?
Thanks,
Jeff
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I think that it is an adjustment screw for the tone of the horn. Tstark
That screw makes small adjustments inside the horn. Mark the position of the slot. Then turn the screw a bit in each direction. Connect a battery or another source of 1.5 volts DC. See if the horn works. Don't turn the screw too far or it may damage the components. Postwar horns are actually buzzers. They need to be precisely aligned to work.
I have heard of higher voltage (up to 20 volts DC) as "shock" treatment, but an old postwar horn may not be able to handle that.
Look for rust or corrosion where the wire from the horn relay enters.
Also be certain the horn has a good ground.
In theory, those horns can be taken apart. But bending those tabs is tricky. And only an expert can put a horn together again.
I think that someone takes horns apart, fixes them, and sells them. He waits until he has a bunch on hand. Do a Web search of "Lionel Postwar Horns." The name should come up.
Some horns that look good don't work. Other horns look like basket cases but they work.
If this horn won't cooperate, get another one.
Good luck!
You didn't ask, but here are a couple of tricks to get a postwar horn working:
1) connect a pair of test leads to a 9 volt battery, or a transformer set to around 9-10 volts. Hold one lead to the case of the horn, and brush the power wire (usually connected to the horn relay).
2) if #1 doesn't work, make the above connection using test clips. Then, using a blunt object that will fit into the opening in the face of the horn, tap the diaphragm. I often use the end of a log, or the back of a small screw driver. It should be a sharp rap, but not hard enough to dent anything. If the horn starts sounding, disconnect the test clips quickly.
