Thank you very much , My trains are not set up and was using the light to see if it worked, when I put a engine on some track the rheostat works perfectly! Thanks again GRAEME BALES
Your rheostat is probably working just fine. It has, even at its leftmost position, a resistance of only a few ohms, while your lamp probably draws only a fraction of an ampere. The result is that there is very little voltage drop across the rheostat wire and the lamp stays at almost full brightness.
It is intended for controlling a toy train, which typically draws a much greater current of several amperes, enough to create a serious voltage drop at the low-speed setting, to slow down or stop the train entirely. Try it with a train, not a lamp.
If the lamp is what you actually want to control and not just what you're using for testing, you'll need a much higher resistance rheostat (or a potentiometer, which is the same thing but with terminals connected to both ends of the resistor). If this is the case, tell us what lamp or lamps you're using, so I can recommend a suitable part.
Bob Nelson
I have it just on a light the off on switch will shut off light but when you slide the wiper to left the light stays bright., instead of getting dimmer. I took off the asbestos off the underside of cover and asbestos is still attached to nichrome wire near where it attaches to post on rheostat. The nichrome wire is not broken that can see, I only have one old transformer that you would use rheostat on, all the others are much newer. I would just like to get to work I had one like this 70 years ago when I got my first train.
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. thanks Graeme
In what way does it not work? Does the train continue to go fast when you move the handle to the left? Or does the train stop when you move the handle to the left? Does the wiper touch the nichrome wire? Is the wire wound around the ceramic tube? Are there any breaks in the wire? Unless the asbestos was flaking apart, it probably would have been safer to leave it in place. But, since you removed it, how is the nichrome wire now insulated between the tube and the terminal?
Could you post pictures of it so that we can see exactly what you have and its condition?
Larry
I have the asbestos cleaned off the cover . The on off switch works and power goes through as it should but the slow fast part of rheostat does not work. any thoughts. Thanks Graeme Bales
First, let me warn you that that white stuff inside the cover and around the wire is asbestos. Caveat reparor.
There should be a nichrome wire wound around a ceramic tube from one end to the other. The right end of the wire should go through a piece of asbestos insulation and be fastened to the bottom ot the right rear terminal. The wiper should touch the underside of the coil of wire. The front end of the wiper should touch the front bar when the switch is on.
Does anyone know how to fix a #81 rhostat the on off switch works but the speed control doesn't work.
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