# Lionel KW Transformer - Open Winding?



## Tumbleweed (May 30, 2014)

I have a Lionel KW transformer which I am trying to restore. Cosmetically, it is in great condition and looking almost brand new throughout, except for the insulating paper around the windings which looks dark, hard and dry. I don't know if this is normal for a transformer of this vintage or if it means it has been exposed to some above normal heat over time. 

When I connect the transformer to ac power however, my meter can’t find ANY dc output anywhere on any of the binder posts (even though the transformer is humming and obviously on and even with the controls all the way on full). I checked the wiring though out and did find that the rectangular wire which connects one of the windings to the circuit breaker was broken off at the circuit breaker. I thought that surely it was the cause of the problem, however reconnecting that wire made no difference. There is still NO output anywhere on the terminals.

I’ve checked the rollers and they seem fine and the circuit breaker also checks out as closed. The only thing that I can conclude at this point is that there is an open winding somewhere. Is there anything else that I might have missed that could cause my problems? An open winding on this transformer seems so unlikely to me.

Also, if there is in fact an open winding, is there any sense in going any further with this particular transformer? I have considerable professional experience working with electrical and electronic equipment so that part doesn’t intimidate me. It seems to me though that the only way to find a replacement core for this transformer is to buy an identical one and once you do that, you might just as well use the replacement transformer as your primary transformer instead of using it only for parts.

One last point I would make about this transformer is that the insulating paper around the windings is dark, hard and dry. I don’t know if that’s just normal aging for a transformer of this vintage or if it means that the unit has been exposed to above normal heat.

Thanks in advance for any feedback.


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## rkenney (Aug 10, 2013)

The output of the KW transformer is all AC, with the exception of the whistle switch which adds a DC component (half wave) to the track voltage.

Set your meter to AC scales and remeasure! 

The lionel KW user/service manual:
View attachment Lionel KW Transformer User's Manual.pdf


Basic Lionel transformer connections:


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## Tumbleweed (May 30, 2014)

rkenney said:


> The output of the KW transformer is all AC, with the exception of the whistle switch which adds a DC component (half wave) to the track voltage.
> 
> Set your meter to AC scales and remeasure!
> 
> ...


Thanks for the response. That did the trick and it works fine that way! I just couldn't see how it could possibly be an open winding...those things just don't happen!

I had always thought that the output from these transformers was DC, at least the part that operates the engine motors. How do they reverse the direction of the motors with AC? I thought it required DC for that.


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## rkenney (Aug 10, 2013)

Tumbleweed said:


> I had always thought that the output from these transformers was DC, at least the part that operates the engine motors. How do they reverse the direction of the motors with AC? I thought it required DC for that.


Reversing the engines is a matter of reversing the armature windings in relation to the field windings.

The reversing trick is accomplished by the E-motor. Basically a DPDT switch and a solenoid that is activated each time power is applied.


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## TrainLarry (Jan 15, 2012)

The explanation of how the electromechanical e-units work to reverse the older universal AC/DC motors can be found here and here. Quite an ingenious mechanism, and one that is loved by all tinplate railroaders...

Larry


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## callmeIshmael2 (May 28, 2012)

Thanks, Tumbleweed for the thread opener and Conductor Kenney for the Olsen's KW info. I've got two KWs sitting on a shelf downstairs waiting for some love but I've been too chicken to try checking them out. One needs installation of a new circuit breaker and the other (I've been told) just needs a new cord replaced, but I'm a bit overwhelmed with a transformer that size. I just need to bite the bullet and try it. This will help...


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## rkenney (Aug 10, 2013)

callmeIshmael2 said:


> I'm a bit overwhelmed with a transformer that size. I just need to bite the bullet and try it. This will help...


When you do decide to 'bite the bullet', be sure to check the carbon rollers on your KW.

If worn down, replace them, operation with worn out rollers will eventually cause the copper fixture that holds them to dig into the transformer windings - resulting in shorted windings and effectively 'trashing' your transformer.

Carbon rollers are readily available from parts houses and Evil-bay.


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## servoguy (Jul 10, 2010)

When you install the rivets to hold the rollers, solder the rivets to the arm rather than trying to upset the end of the rivet. The solder makes a better electrical connection than upsetting the rivet. 

When I installed rivets 35 years ago in my first ZW, I noticed that the arms had been somewhat hot, so I soldered the rivets in place. I also had to make the rollers as the only hobby shop in Orlando would not sell me parts. Needless to say, I have not been to that shop since then.


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## gunrunnerjohn (Nov 10, 2010)

I suggest doing both soldering and crushing the end of the rivet. I just crush the end of the rivet and then solder the head to the arm.

Note that you need to put the rivet heads toward each other in the center so the two arms don't hit. If you leave the long end of the rivet there, they'll clash. This is the same for a ZW.


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## callmeIshmael2 (May 28, 2012)

Thanks to all for great suggestions. With this thread in hand, I will soon haul out my KW and get past my self-imposed fears...


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