I’ve just picked up a K Line O27 uncoupler Track, one of those odd items that appears on eBay and nobody wants it. 

Looking at the wiring, it looks very simple compared to a Lionel unit - a single wire to a single button. The printed wiring diagram on the packaging shows the wire going to one side of the transformer. 

I’m intending to fit this unit to my O27 door layout. Am I right in thinking that the wire could be connected to the earth side of the nearest lock-on? 

Original Post

Connecting the on/off button to the power side lockon i think would work, but still subject to the variable voltage of the transformer. Some folks, (like me  like to have uncoupling tracks connected to a fixed voltage terminal for snappy uncoupling independent of the track voltage.

Last edited by Penn-Pacific

Seeing as it is a clone of the Lionel 6149, the electromagnet is grounded through the track and you need only to provide a switched hot through the switch/button to operate.

Ok, understood. I wasn’t familiar with that Lionel unit, my existing O27 ones have the four-wire, two-button set-up. 

The K Line instructions look like this; 


Comparing that to a Lionel lock-on yes, I see that it goes to the centre rail tab. I’d expected it to go to the other side? 

On a larger layout I would go to a fixed terminal on the transformer, but under the circumstances (the door layout is portable, and not really capable of running more than one loco at once) I’ll run it from the traction current. 

I have a coal loader set up to a separate supply, but I don’t want to risk a short circuit 


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I would hook it up to the fixed 12v or so on the transformer unless you have a modern engine that requires a constant track voltage. 

If you use a lock out, using conventional control and have engines with 2 way e Units with out neutrals, you will have the train powered up and maybe moving to have power to the uncoupling track.

It is easy to hook up the transformer with one wire going from the constant 12v terminal, to the switch and then to the electromagnet on the uncoupling track.  You should not need a second wire if the other wire from the electromagnet is hooked to the outside rail of the track at the uncoupling track.  This is the way my 19 uncoupling track are hooked up.


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