Someone asked me how to estimate the required wattage for Marx accessories. Although I don’t recall Marx ever issuing any specific guidance, it’s easy to do yourself.
First, count up the number of light bulbs in each accessory. Each bulb will use 2.7 watts or .15 amps. Since most Marx accessories had a bulb or two, this will probably make up the bulk of your required wattage.
Motorized accessories, such as a whistling station, will need 10-15 watts per motor. If they have lights, be sure to include those as well.
Some Marx accessories were powered by solenoids. I don’t have an accurate way to measure their usage, so assume each will need about 5 watts. For switches there’s no need to worry, as they run only very briefly, but for something like a crossing gate, you can’t completely ignore it.
The other thing to consider is how much will be powered at once. The bulbs are likely to be fairly constant, but your gates may not be running at the same time as your whistle. If that’s the case, you can just take the higher of the two numbers.
It’s pretty safe to say that a 40 watt starter set transformer will have enough wattage for 10 bulbs with enough left over to power a motorized accessory or a crossing gate or two. A 75-watt box, which can still be pretty cheap, can power almost double that.
But if you’re concerned about having adequate power and want to get accessory power on the cheap, consider using a computer power supply, which can provide a couple hundred watts at 12 volts for around 15 dollars.