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All about the Lionel ZW

The Lionel ZW is Lionel’s most iconic transformer of the 1950s and 1960s, and perhaps one of its most iconic products, period. Everyone wanted the two-handled, football-shaped, 275-watt powerhouse that was the ZW. It was one of Lionel’s more venerable postwar products, lasting on the market for 18 years from 1948 to 1966. It replaced Lionel’s former top-of-the-line transformer, the Z.

Finding original ZW instructions or an original ZW manual online is a bit difficult, but there’s plenty the original instructions don’t mention.

Lionel ZW

The Lionel ZW has four sets of variable outputs, four throttles, two whistle/direction controls, a power light, and a short circuit light.

The ZW is just like any other transformer in that you need to check it for safety before you use it. Also, although a lot of people forget to mention this, it’s important to unplug or otherwise disconnect the power when you’re not using it. I have my transformers plugged into a power strip with an on/off switch so I can switch them all on and off at once.

The ZW is cheaper today than it was even a decade ago. Modern transformers with higher wattages put a dent in the ZW’s market and resale value. That said, the ZW is still an excellent transformer. Pair up a ZW with one of Lionel’s better postwar locomotives like a 675, and you’ll understand postwar Lionel’s enduring appeal. Reconditioned ZWs sell for $125-$150. As-is or untested ZWs can sell for less than $100, depending on what’s missing. A modern-production Lionel ZW-L sells for several hundred dollars.

Lights and pinout

The ZW has two lights. The green light is the power indicator. If the transformer is plugged in, you should expect this light to light. The red light is a short-circuit indicator. Normally you should expect this light to be off.

The ZW has four sets of posts on the back. Posts A-U and D-U correspond to the two big handles on each end. U is the common post, which goes to the outer rail. Posts B-U and C-U correspond to the two smaller dial controls next to the bigger throttles.

Unlike many other Lionel transformers, all of the ZW’s outputs are variable. It doesn’t have any fixed-voltage outputs.

Although a ZW can run other makes of trains, be very careful with a ZW and Marx or American Flyer trains. ZWs can output 20-21 volts, which is well above the 15 volt maximum that Marx and American Flyer motors are designed to handle. Use a voltmeter if you’re going to run non-Lionel trains.


The two large handles on either side normally control your trains. The levers next to the throttle control the direction and the whistle. Push the lever forward to activate the whistle, and pull the lever back to interrupt power and change direction. Unlike the slightly smaller KW, the ZW can activate both whistles simultaneously if you wish.

The two smaller dial controls are less convenient to use for trains and they don’t have a whistle capability or a direction button. To change the train’s direction, you have to turn them down to 0 volts and then back up. Because of this, a lot of people use B-U and C-U for accessories and the other two handles for trains. That said, if you want to run four trains off a ZW, you can.

You should consider one thing before you power accessories with a ZW. When the carbon rollers never roll, they tend to become brittle. The best way to prevent that is to adjust the voltage up or down a half volt every once in a while. Or you can power your accessories with something else. A Lionel LW is ideal, or you can even use a PC power supply.

Lionel ZW power distribution

A common question is whether the Lionel ZW distributes its power evenly across all of its posts. The answer is no. The wattage is split across all four posts, but that doesn’t mean a set of posts is limited to 67 watts of output. When you have a low load or no load on a particular set of posts, the balance of available power is available to any of the others. If you only want to use one handle, all of the ZW’s available power goes to the set of posts associated with that handle.

This arrangement is easier to engineer, and also provides more flexibility. If the power distribution was strictly even, a ZW would be no better than teaming up four starter-set transformers, and the four starter set transformers would be a good deal cheaper.

Common repairs

The most common problem I see on the ZW is broken binding posts, which cuts off power to one or more of the controls. There’s an easy fix, and a really easy fix. The circuit breaker is a less common repair, but not expensive.

The whistle control can also get a bit wimpy. You can fix that by replacing the old rectifier discs with diodes, which is something I’ll cover in the near future.


Early ZW transformers from 1948-49 had a 250-watt rating, the same as a Z. They also output slightly higher voltage than later ZWs, with a range of about 7-21 volts.

In 1950, Lionel released a revised version with a 275-watt rating. Its voltage output is about 6.5-20 volts. In 1957, Lionel revised the design again. the ZW-R doesn’t say “R” anywhere on the transformer itself, but the changes made it easier to assemble and theoretically, a ZW-R hums less than an earlier ZW.

Lionel also made a VW transformer from 1948-1949. It looks just like a ZW but has a smaller 150-volt rating. Aside from that the Lionel VW is just like a less powerful ZW, with four variable outputs and direction and whistle controls just for the outer handles.

The modern-production ZW-L outputs 620 watts. Unlike its vintage predecessor, it has voltage and amperage gauges.  Lionel’s release of the ZW-L is one of the reasons vintage ZWs cost less today.

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10 thoughts on “All about the Lionel ZW”

  1. I am trying to find out what the input amperage would be on a zw so that we could determine how many could be connected to a 15 amp ac circuit. The owner tells me he has a 275 watt at 18 volt unit. Thanks

    1. A single ZW running full bore can draw 15 amps on its own. How much it’s actually using will vary depending on what’s plugged into it on the layout.

    1. Thanks. I don’t think anyone knows production numbers. I don’t think Lionel had any reason to track them that closely. They aren’t hard to find, at any rate.

  2. I have a ZW250 which I took in for service. The whistle did not work for a williams train engine I was using. The repair man told me that this transformer will not operate whistles on modern train engines. Is this true? I thought that any transformer with a whistle control could activate the whistle on any lionel or compatible engine.

    1. I understand the modern electronics aren’t always too keen on the traditional rectifier disc in the older transformers. But as far as I know, if you replace the disc with a diode, that eliminates the incompatibility. And the diode still works just fine with the older engines. I’m a little surprised the shop didn’t offer to make that modification for you.

  3. Thanks so much for your reply. I suspected that this would be the case. I will see if he can do this.

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