All about the Lionel LW transformer

The Lionel LW Trainmaster is a 125 watt transformer that Lionel produced from 1955 to 1966. They are reasonably durable and Lionel made them for a long time. That means you can find them easily on the secondary market. They can be expensive if they have their original box and paperwork. But if you just want to run a train and don’t care about the paper, you can get a serviced LW for $50-$60, and an as-is one for under $40. At 125 watts, it’s the most powerful single-handle transformer of the postwar era.

The LW is a quirky transformer so there are some things about if you need to be aware of if you have other Lionel transformers, but as long as you keep those in mind, it’s a fine transformer that will serve you well. The quirks have nothing at all to do with reliability. Lionel just designed its layout a bit differently than many of their other models. In some ways it’s the ideal accessory transformer. We’ll cover that later.

One thing to keep in mind: Unplug the LW when you’re not using it. It doesn’t have its own power switch. I plug my transformers into a power strip and turn all of them on and off with the strip’s on/off switch.

The LW can also run Marx or American Flyer trains, though it’s not as good of a choice as, say, the 1033 as its maximum voltage is 18 volts. Those brands used a lower voltage than Lionel typically did, so you can damage them if you run them for long periods of time at 18 volts.

The lens cap on the LW’s handle is often missing, but replacements are available if you need one. Or you can live without one and get the transformer more cheaply–it’s your choice.


Lionel LW transformer
There’s nothing wrong with the Lionel LW, it’s just wired differently internally than other Lionel transformers so its pinout can confuse people.

There are five posts on the transformer. Two of them are labeled post A; they are connected together inside and functionally identical. Post A goes to the outer rail of your track (post 2 on a Lionel CTC lockon, or the black wire on Fastrack); post U goes to the center rail (post 1 on the lockon, the red wire on Fastrack). This is the exact opposite of most Lionel transformers. If you have multiple Lionel transformers and you use them together, you might want to relabel the posts on the LW to match. Lionel was courteous enough to also label the A posts as “Common.”

For accessories, connecting posts A and C gives you 14 volts; connecting posts A and B gives you 18 volts. Generally speaking, you’ll want to run your accessories at 14 volts. Using post A and U for the train doesn’t preclude you from using post A and C for accessories. This setup is ideal for running non-derailing switches; just power the switches with the C post and they’ll get 14 volts for quick snapping action. For accessories that work better at 18 volts, you can use posts A and B. These pinouts make the LW an excellent accessory transformer.

You can also connect posts B-C to get a 5-volt fixed voltage, but this setup doesn’t have any circuit breaker protection, so use an external circuit breaker if you use this combination.

If any of the binding post nuts are missing, you can get replacements from Ebay. But since the posts are threaded 6-32, so you can just use an ordinary household 6-32 nut if you wish. If you prefer a knurled nut and want to get something today, head to Home Depot. Home Depot has suitable replacements in brass (which are cheaper) or stainless steel (which match the transformer better). Unfortunately, neither of them match the appearance of the original Lionel posts exactly. Then again, they also cost half as much.

Safety and Troubleshooting

I have covered basic transformer troubleshooting before in another post; everything there applies to the LW. When it comes to repair, the most common thing it needs is a replacement power cord.

Using multiple LWs

You can team up LWs for different loops of track on the same layout; just phase them first. As the cost of ZW and KW transformers has come down, this practice isn’t as common as it once was. There was a time when you could buy two LWs for half the cost of a single ZW and end up with only slightly less usable wattage. Today my recommendation for someone who can’t afford a ZW would be to spring for the KW and use the LW for lights.


LIonel LW transformer
This diagram shows the operation of the controls on the Lionel LW transformer.

The LW has a handle and two pushbuttons. The throttle works in the opposite direction of other Lionel transformers, so be careful with it. The LW doesn’t have a built-in voltmeter, so if you want to see how much voltage it’s delivering, you need to add an external voltmeter.

The button closest to the posts controls the direction of the train and the button below it operates the train’s whistle or horn. Push the top button to change the train’s direction (most Lionel trains cycle from forward to neutral to reverse and back to neutral). Push the lower button to operate the train’s whistle. The LW delivers negative polarity with its whistle button, so with modern locomotives, it may activate the bell instead of a whistle or horn. To control a whistle, you’ll have to reverse the polarity to the track. That can cause complications in a multi-transformer setup. So a better solution is to add a modern whistle controller. K-Line’s controller was much more reliable than Lionel’s.

One thought on “All about the Lionel LW transformer”

  1. Thanks Dave, I have one and I wasn’t quite sure what the different terminals were. You answered that. One Q.Why does the whistle make the train go faster. I’m using Post U & A. and this transformer.

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