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10 tips for buying a power supply

By Bob Keller | January 14, 2021

How to pick the best power supply for your toy train layout

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A display featuring an MRC Throttlepack, MTH Trains Z-400, and a vintage Marx transformer.
Highly detailed Lionel toy train layout with many collectible items.
Trains aren’t the only things that need power. When choosing a power supply, factor in lights and accessories like the ones on this Lionel layout, too

Picking the right power supply for your railroad has one toe in the present and one in the future. It will need to run what you have today and will be expected to perform just as well years from now.

Transformers aren’t cheap, but today’s O and S gauge hobbyists have a better selection of brands and power levels than at any time in model railroading’s history.

Having a rough idea of the power you need is the best place to begin. For example, a locomotive with two motors may draw more than 100 watts. An accessory powered by a motor can use 25W; a Vibrotor-powered accessory may use 20W; and a simple light bulb in a streetlamp can use from 3 to 5W.

Factor in modern locomotives with sound, speed control, and motorized smoke units and you’re rapidly approaching postwar Lionel ZW power output of 275W!

Simply put, the more motors, lights, and sound/command systems you have, the more juice you’ll need. Do you have a long passenger trains with interior illumination? How about an exceptionally long, heavy freight? Yup, you guessed it — you’ll need more power.

Older, postwar cars don’t roll as freely as modern cars with needle-point axles. Modern cars roll freely but can weigh two or three times more than a similar vintage car.

Before you open your wallet to buy a transformer at a train show, hobby shop, or online, ask the following questions:

A display featuring an MRC Throttlepack, MTH Trains Z-400, and a vintage Marx transformer.
From left, an MRC Throttlepack, MTH Trains Z-400, or a classic Marx transformer might work for your layout. Asking some questions will help you determine what you need.

1. What’s the total power output per throttle? The higher, the better.
2. How many trains can it control? Two throttles are good, but if you’re using the transformer simply to power Lionel’s TrainMaster or Legacy systems, or MTH’s Digital Command System, separate throttles aren’t an issue.
3. Does it have an accessory output? One is handy, even if you don’t have immediate plans to use it.
4. If there is an accessory output, is it fixed or variable? A variable auxiliary output lets you set a power level to achieve the desired brightness for streetlamps or interior building lights.
5. Does it have a horn/whistle button? A must-have with today’s trains.
6. Does it have a bell button? Ditto.
7. Does it have an LED or meter to show output? This is always handy and more accurate than moving a power handle to “full speed.”
8. What are the connecting terminals like? Banana plugs give you a nice, snug fit at the transformer, but few lockon sections use this type of plug.
9. Will it meet my future needs? More power is never too much; see no. 1. Initially, it may be an expense, but it also means you’ll have plenty of juice in reserve.
10. What does it look like? Probably the least important question to ask, especially in this era of control boxes connected to big power blocks somewhere under the table. While the postwar ZW transformer may win in the studly looks department, a string of smaller Lionel no. 1033s hooked up in series may get the job done just as well.

If your power requirements are minor, you may be able to get away with the transformer that came with a small set. If you know your power demands will be eventually be major, you may as well bite the bullet and buy a robust supply early. You’ll have the power you need to run your trains today, with growth potential for the future.

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