faulty 12vac dimmer/switch: revised

Thread Starter

atlantis43

Joined Apr 30, 2014
15
This is a corrected version of a recently submitted post, which had some errors in description of item:



I'm having problem with a 12vac halogen lamp rotary dimmer/switch, which does not turn "off", with light returning to partially "on" when switch in "off" position.
(Sometimes bulb actually turns off, but if I return to lamp later I find that bulb is again lit!)
Sorry that I can't take a clear picture of this mini-switch, but I've attached the best I can do of the interior of the switch, and I hope that you'll excuse the verbiage----a picture is worth 1000 words :).


The original switch has 4 terminals, 2 on top, and 2 on bottom , but only 2 wires (one connected to a top terminal marked ‘B’, and the other connected to a bottom terminal ) which connect to another box of electronic circuitry (which connects to 120vac, and also to the bulb itself). There also is a "jumper" wire connected from the other “top” terminal to the other bottom terminal. There are no other identifying markings on the switch.

I purchased a replacement dimmer unit, but didn't realize that it was for a 120vac bulb, and was therefore unsuitable. It had a similar looking switch/rheostat (with marking B500k), which was solder-mounted to a circuit board by its "top" two and "bottom two terminals.

When I disassembled the two switches, they both had identical contact assemblies on the bottom unit (see picture), but the actuator facets of the two switches are not identical, so I can't just switch partial assemblies from one to the other. I also can’t see whatever is in the top part of the switches.

I'll try to help describe what is shown in the attached picture, which is:
1) a small fixed contact shaped like a small spoon, to which one terminal is connected. This is the smaller shiny object in the picture
2) a larger half-circular metal contact, with a small pin at one end and a contact knob at the other end. This is the larger shiny object clearly evident in the picture.
3) a piece of springy metal (seen end-on in the picture, so it is barely visible) which is mounted inside of the above two structures, and
I guess serves as the on-off switch when moved by the actuator ridges on the knob.

My Question is:
What is the “jumper” wire for on this item.
Is the above-mentioned "jumper" wire on my original switch the thing that converts a potentiometer into a switch-potentiometer? If I were to install such a jumper on the replacement potentiometer, will it have the same effect?
(I'm assuming that my original unit was also a B500K pot).

I hope that I've given a clear enough understanding of the problem that someone might be able to provide an answer.
 
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