All about the Lionel RW transformer

Last Updated on August 17, 2018 by Dave Farquhar

The Lionel Multi-control Trainmaster RW is a sturdy tin box of a transformer from early in the postwar era. The presence of a whistle controller is the only thing that really distinguishes it from a prewar transformer. Lionel made it from 1948 to 1954. If you want to know all about the Lionel RW transformer, you’ve come to the right place. You probably won’t find a copy of the original instruction manual online but this will tell you all you need to know.

The RW doesn’t get as much attention as its contemporary, the 90-watt Lionel 1033. Maybe that’s because the 1033 is easier to find. For whatever reason, the RW is easy to overlook, but don’t. There’s nothing inherently wrong with the RW. You can mess it up if you take it apart wrong, but that’s easy to fix. At 110 watts it’s not a monster transformer but it’s not a slouch either. The only Lionel transformers that give you more wattage per handle are the LW and the ZW.

Today you can get a serviced RW for about $45, and an as-is one for $20-$25. There’s not a lot of price difference between it and a 1033, and with all due respect to the 1033, the RW is more than worth the $5-$10 price difference.

Even someone who has a larger transformer or multiple larger transformers for the layout might be interested in a RW for the test bench, as it has all of the functionality someone would need for testing locomotives and whistling tenders.

And if, like me, you like to run older tinplate trains, the RW looks like a prewar transformer while still having a circuit breaker and a whistle controller if you decide to run postwar trains.


Lionel RW
This diagram shows all of the controls and the pinout for the Lionel RW transformer.

There are five posts on the back of the transformer. Post U goes to the outer rail of your track; post A or B goes to the center rail. Use Post A if you want 9-19 volts or use post B if you want 5-16 volts. What’s the difference? Post B is more useful for postwar trains and a necessity for using an RW with Marx or American Flyer trains. With Post A you could run Standard Gauge trains if you wanted. But I think the B-U combination is more useful.

For accessories, connecting posts A and D gives you about 19 volts; connecting posts B and D gives you 15 volts. Posts C and D give 10 volts. These three combinations have circuit breaker protection.

Connecting posts A-C gives 9 volts, B-C gives 6 volts, and B-A gives 3 volts. None of these combinations have circuit breaker protection, so use an external breaker if you use any of these combinations.

The LW is a little nicer for accessories but the RW gives a useful set of voltages.

If any of the binding post nuts are missing, replacements are available on Ebay, but since the posts are threaded 8-32, so you can just use an ordinary household 8-32 nut if you wish. If you prefer a knurled nut and want to get something today, Home Depot has suitable replacements in brass (which are cheaper) or stainless steel (which match the transformer better), though neither of them match the appearance of the original Lionel posts exactly. Then again, they also cost half as much. And since the posts are on the back of the transformer, you may never notice the difference anyway.

If you find yourself switching between post A and B for track power, here’s a trick. Add an ordinary 8-32 nut over whichever wire you use for accessories to hold it in place while changing power. This could save you some frustration.

Safety and Troubleshooting

I have covered basic transformer troubleshooting before in another post. Everything there applies to the RW. When it comes to repair, the two most common things it needs are a replacement power cord or a wiper fix, which won’t require any parts.

The circuit breaker is supposed to trip if you short the A-U or B-U posts after about 12 seconds. If it doesn’t, you need to replace the circuit breaker. After you open up the transformer, the circuit breaker is in the bottom of the case on the right-hand side looking from the front. A single #4 sheet metal screw holds it in place. You can replace it with any 6-amp auto reset circuit breaker that fits. Desolder the wire from the front side and attach it to the new breaker either with solder, or crimp on a quick-connect plug. Then desolder the wire bundle from the back side and connect those wires to the other lug on the breaker, either via solder or crimp on a quick-connect plug.

Using multiple RWs

You can team up RWs 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 three RWs for less than a single ZW and end up with slightly more usable wattage. Today my recommendation for someone who can’t afford a ZW would be to spring for the KW and use the RW for lights.

But if you already have multiple lower-wattage transformers there’s no reason not to use them together.

The RW as an accessory transformer

Many enthusiasts use separate transformers for trains and accessories. The RW makes a good accessory transformer because of its relatively generous wattage of 110 watts and its variable output uses a copper contact rather than a carbon one. You can adjust the variable output to the voltage you want, remove the handle if you don’t want to accidentally change it, and send a very specific, fine-tuned voltage to your accessories. The advantage to using a copper variable output for this is that the copper doesn’t degrade and become brittle over time. If you never move a carbon roller, it does eventually get brittle and crack.

So while the RW doesn’t have the star power of a KW or ZW, it’s actually a better choice to run your lights and switches if you need to fine-tune the output.


The RW has a handle to control the throttle. It 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 RW also has two buttons, a black button to control the whistle and a red button to change the train’s direction. This can be less confusing than using a handle to control the direction and buttons like many other postwar transformers.

The RW lacks a bell/horn controller for modern Lionel diesel locomotives. To control a bell or horn, you’ll have to reverse the polarity to the track. That can cause complications in a multi-transformer setup. You can also add a modern horn controller. K-Line’s horn controller was much more reliable than Lionel’s.

Always unplug your transformer when you’re finished, as the RW lacks a power switch. I plug all of my transformers into a power strip and use the on-off switch on the power strip to turn all of my transformers on and off at once.

If you found this post informative or helpful, please share it!

6 thoughts on “All about the Lionel RW transformer

  • February 13, 2017 at 2:59 pm

    Great write up. I’m a model railroad noob of the highest order, and even I could understand what you were saying.

    • February 13, 2017 at 5:00 pm

      Thanks! I hope you found it helpful.

  • November 16, 2017 at 12:10 pm

    Great, awesome, wonderful. Thank you !! This was VERY helpful. Awnsered more ?’s didnt even know i had.

  • November 24, 2018 at 5:29 pm

    Any possibility of a schematic for it?

  • December 19, 2018 at 2:14 pm

    This was very helpful thank you. I’ve had my Lionel Train with RW Transformer. First time l really understand the back of the unit and now know I should use the BU Settings. Thanks again

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