How I fixed a Lionel RW transformer

Last Updated on November 21, 2018 by Dave Farquhar

Lionel RW
The Lionel RW transformer, produced from 1948 to 1954, is one of Lionel’s larger single-throttle transformers.

I had a Lionel RW transformer that I bought nearly 10 years ago, at one of my first estate sales. I’m sure I remember using it after I bought it, but it was far from in working order when I found it this time. The accessory posts all showed voltage, but the critical A and B posts showed zero volts when connected to the U post, no matter how I turned up the handle. So while the transformer could power accessories, I couldn’t run a train off it using the variable output.

And I was uncomfortable using it without knowing exactly why part of it wasn’t working.

Fixing turned out to be easy, however.

The first thing I noticed was that the control handle was really loose. Some handles just lift straight up; this one is secured with a screw. I removed the screw, pulled it up, and noticed a problem. There’s a notch on the voltage control shaft for the handle, but the handle hadn’t been on the notch. So I tried pushing it down on the notch, how it’s supposed to go.

No dice. I powered it up and tested it, and still got my zero volt reading.

Lionel RW underside
The underside of the RW. The four shiny places without paint in the corners are where the screws come out.

So I took the arm back off and removed the four screws on the underside to remove the cover. Always unplug a transformer before opening it up!

Underneath the voltage control shaft, I saw my problem. There’s a power arm under the shaft–really just a strip of copper with an indentation on it–that engages the coil underneath the top bearing plate. Well, my power arm was curled up and not coming into contact with anything at all. Someone at some point had found a way to turn the handle too far, and it had sprung out of place.

Lionel RW control arm
The control arm is the copper piece with a big indentation on the end resting on the piece of black plastic near the center of the photo. If you don’t see this piece, it’s curled up inside the transformer.

So I reached in with a wooden stick and pulled the control arm back up on top of the coil. The indentation touches the coil, and wherever it happens to touch determines the voltage the transformer outputs. I put the handle back on the shaft temporarily and tried turning it. It felt much tighter, and made that slight clicking sound you expect from a transformer as you turn up the throttle.

So I removed the handle again and put the top cover back on, replaced the handle, plugged the transformer back in, and tested it. 6.5 volts on posts B-U, and 10 volts on A-U. I turned the throttle up, and the voltage increased, topping out at a little over 19 volts on A-U. Perfect. I unplugged it again, replaced the four screws, and called it a day.

Transformer repair doesn’t get any easier or more straightforward than that. If you ever come across a Lionel RW transformer with a really sloppy and loose throttle handle, it probably has the same problem.

There’s one other common problem that RWs and most other postwar transformers face: a worn-out rectifier disc. I cover replacing the rectifier disc with a diode in another post. If you need help setting it up, I cover that too. I also did a quick paint touch-up on mine to make it look a little nicer.

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