How to connect a Lionel transformer to track

Last Updated on December 4, 2022 by Dave Farquhar

If you’ve lost the original instructions, it’s certainly not obvious how to connect a Lionel transformer to track. Especially if someone else always set it up. But don’t be intimidated. It’s low voltage wiring. And it’s usually only four connections. Here’s how.

Safety first

Before setting up any Lionel train, give the transformer a visual inspection at the very least. Make sure the power cord isn’t frayed or broken and the case is intact, with no breaks or cracks. I have a more thorough safety inspection I put transformers through. If your transformer isn’t in good condition, lots of professionals refurbish transformers and sell them on Ebay at reasonable prices. If you’re not sure what to get, here’s some advice on how to choose a Lionel transformer.

There is a misconception that old transformers are unsafe to use. Transformers don’t go bad just from aging. Consider your doorbell, for instance. That uses a transformer. The doorbell in my house, built in the early 1960s, still uses the original transformer the builder installed. It’s never been a problem. Sure, that’s anecdotal. But I have a good relationship with my realtor and house inspector, and they tell me that’s typical. Even on houses dating to the 40s and 50s, it’s more unusual to see a replaced transformer than the original.

I also like to test the track. Troubleshooting is much easier if you start out knowing that all the track is OK.

Connect a Lionel transformer to track via a lockon

Lionel CTC Lockon
A Lionel CTC lockon, properly installed. A Lionel transformer connects to track via a lockon on pre-2003 Lionel train sets.

Up until 2003, Lionel train sets shipped with tubular track. Traditional Lionel tubular track connects to the transformer with a lockon, a small fiber board with contacts that clip onto a track, and two wire terminals. The lockon connects to your center rail and one of your outer rails. I always connect the lockon so the terminals sit outside the loop of track. It’s easier that way, since the transformer usually sits outside of the loop.

The lockon has two clips that contact the rails on your track. One clip sticks up higher than the other. Slide the lower clip, the one closer to the terminals, onto the outer rail, holding the lockon at about a 45 degree angle with the terminals above the track. Then tilt the center up until the taller clip snaps onto the center rail. Properly installed, it looks like the image to the right. Connecting it any other way results in either an incomplete circuit or a short circuit. You don’t want that.

connect Lionel transformer to track
The wires connect to the lockon via Fahnestock clips like this one.

Then you connect your wires. I like to use black and white wires of at least 18 gauge. You’ll probably use whatever wire you have in the box. Make sure it’s not frayed and the insulation isn’t broken. And as long as the wire doesn’t feel hot when you’re running the train, it will be OK.

The lockon has two terminals, called Fahnestock clips, that wires connect to. These are spring loaded, and when you press down on the spring, you slide the wire into the opening, and then release. The spring grips the wire and holds it in place. Twist the wire so it fits the opening, and just ensure it doesn’t contact anything other than the clip you inserted it into, to avoid short circuits.

On the transformer side, the wires connect to screw-on terminals. Loop the wires into a C so they stay on the terminal, and tighten the nut down onto the wire to hold it in place. Here’s a more thorough explanation if that part isn’t completely clear.

The terminals on the lockon and transformer are labeled. Slightly more often than not, and especially with smaller Lionel transformers, you connect A to 1, and U to 2. A1 and U2. Like the steak sauce and the rock band. I have a large collection of Lionel transformer pinouts if you want to be certain.

But don’t worry too much. If you get it wrong, the worst that can happen is that either your train runs at one constant speed, or the bell or whistle controller doesn’t work right.

Connecting additional lockons

If your train runs at inconsistent speeds, you can connect multiple lockons to the track. Just make sure you wire them all consistently. Here’s how to add lockons to the track. But keep it simple at first. Get the train working with one lockon and one transformer connection first, then add lockons if it’s necessary.

I’ve also found that treating my track so it stays clean also makes the trains run at a more consistent speed.

Connect Lionel transformer to Fastrack

Lionel train sets manufactured after 2003 come with Fastrack, which has integrated plastic roadbed. Connecting Fastrack is pretty simple, because the wires are already attached and they’re color coded. Modern transformers have red and black terminals. Simply connect the red wire from your Fastrack to the red track terminal on your transformer, and the black wire from the Fastrack to the black track terminal on your transformer.

If you’re using Fastrack with a vintage transformer, try black with the U terminal first, and red with the A terminal. The worst that can happen if you reverse the A and U terminals is the bell and whistle buttons don’t work right.

Adding additional wires to Fastrack is also possible, but many small layouts can get by with a single connection, especially if you treat the track.

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