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Hello all,

I am trying to find a schematic diagram of a K-line K-950 transformer so I can replace the control potentiometer/switch that broke off at the shaft making it impossible to turn on or off now. I took it apart and have removed the bad control potentiometer/switch and now need the part number so I can replace it and repair my train transformer. The part number that is on it gets me no where. I've looked on line but have had no luck, The transformer is still good but I have no way to turn it on or off now. Could someone please point me in the right direction so I can run my old 1960's era train again? Maybe even the part number too? Any help would be appreciated


Original Post

Thank you for the replies back. Okay if finding the potentiometer/switch is not possible and it is an undersized transformer,what suggestions do you have? The train I have is very low key. It is a Lionel 242 Scout,built between 1962 and 1966.  Yes, I know it is a beginners train,but it was a gift from my dad from the early 1960's for a Christmas present when I was just a child,and it has sentimental value to me. I just dug it out a couple of years ago and was amazed that it still worked. I even figured out the problems with the extra rusty track my dad could never figure out as to why it would not work. I rehabed the track and it works fine now.I have recently improved this "throw away train"  as some call it, to pull more than just 3 or 4 cars as it's original advertisement  said about it.  I applied Bullfrog Snot to the traction wheels and it now pulls up to 12 cars. I kind of like the nostalgia involved with this train and the memories it holds playing with my dad back in the day. I'm not as big a hobbyists as some of you are. I'm just wanting to see if I can get it running again like it was before the control broke on the transformer. I do appreciate any suggestions you guys may have since you folks are pros at this and I am not. I'm a retired electronics technician and like fixing things. This is a simple fix if I can only find that part,but that does seem not possible now. One option I have considered is finding a now defunct same transformer and taking the part I need out of that and fixing it,but most people throw  these away nowadays and even that would be hard to find.

Originally your set would have come with a Lionel 1016 or 1025 style transformer. That is enough to get the train moving and complete your set - that's about it. Fortunately, these are relatively inexpensive and easily found under the table at train shows and the good ol' type hobby shops. However, if you plan on expanding your single train empire with a few accessories and lighting, an RW, LW, or CW80 transformer would be a huge upgrade. However, these have their limits and if you have dreams of multi-train operation, illuminated and operating cars, switch tracks and such, than a classic KW or ZW may be of interest, but these are pricier options. Then there is diving in with both feet and getting something modern with command control capabilities such as the ZW-L, but it seems that would be extremely premature and even more out of your budget.

Tom, Since you are an electronics technician you could unsolder the 3 wires going to the potentiometer and the 2 wires going to the SPST switch on the pot.

Use your VOM meter to measure the pot. It will have 3 terminals. Measure the outer 2 to determine the resistance of the pot. Now you need to determine if this is a linear or taper pot. Use your VOM meter again (on the ohm setting) and put it on one outer terminal and the middle terminal. Slowly turn the pot knob from side to side and watch the meter to see if the resistance changes smoothly or tapers. Even if the shaft is broken you may be able to turn it with a pair of needlenose pliers. Now that you know the resistance of the pot and the taper you can purchase one from one of many electronic supply places. Digikey, Mouser, Jameco, etc. You should be able to get a pot with a SPST switch. If it just the switch that is broken you might be able to replace it with a separate small toggle switch. If the shaft is broken and you cannot move the pot shaft at all you could still measure the pot resistance (outer terminals). I would guess it is a linear taper. If it is just the switch on the pot that is broken you could plug the transformer into a plug strip and use the on/off switch on that to turn on/off the transformer. It would probably make more sense to just purchase a new transformer. Since you like to fix things, you can figure out the pot resistance and purchase one. While the pot make have the 3 terminals go to a circuit board inside you can cut those. A new pot could be placed in the case and you could solder wires to the 3 terminals on the pot and solder them to the circuit board.


I found one(K-950) on ebay for 5 bucks and ordered it. Even if this one I ordered is bad I can take the potentiometer out of it and put it in the known working one. This pot has numbers on it but are useless to find another one since they were made in the early 1990's and also in China. It will not turn but broke off when it was turned off,so that helps some.   I had already measured the resistance,it is  500k ohm and is marked 3 amp 125 VAC. I looked on line for the same thing,but what I find won't fit inside the case or mount on the circuit board inside.

I will keep the suggested other transformers in mind for future reference if I decide to expand my train empire. Thank you for the information.Right now I have 55 feet of track and this broken transformer had worked fine to get it going around all that track with 12 cars even since applying Bullfrog Snot. I don't know if the voltages (17 ac volts) are the same for  these other transformers and will work with my old train.Right now it's not really what I am seeking. This train(the 242 Scout) is not that powerful to require higher wattage transformers. Again this is only a small hobby I am dabbling in. My daughter just had my first grand child(grandson) and am trying to get this going to give to him some day when he gets old enough to keep the tradition going to the next generation. This train has set in the attic for 50 plus years. The track and pins were rusty and I fixed all that and it works great now. For some reason and I am not sure why,the control knob broke off at just the wrong spot. Maybe it was dropped and had a slight crack which you couldn't see under the knob and eventually broke is my guess. I will keep this post up to date as I figure it out. I really do appreciate all the help though. When something is this old,it's nice to know there is still support  around like this website forum.

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