Hello
I have this transformer from the 1940s I believe. I opened it and found out why it was not working very well on one of the two outputs. A good clean up of the wiper arms and it is working fine now.
There is what looks like a large wire wound resistor in there and I’m curious what it’s purpose would be in a transformer like this?
Thank you.
Welcome aboard, @ruko!
I can’t answer your question, but welcome to the forum, ruko!
Probably for voltage dropping, where the transformer couldn’t be made with different taps.
I believe the resistor is there to limit current passing through one or both of the indicator lamps, rated for a lower voltage.
-El
Welcome aboard Ruko! 
That resistor, part number R-41, is the heating element to heat & trip the circuit breakers(there are two). The element is center-tapped, so when one track circuit is overloaded, that side of the element gets hot and trips without tripping the other track circuit.
This turned out to be a complicated and expensive way to accommodate the rather neat feature of not bricking the entire transformer while the one breaker cools & resets, but it was discontinued in favor of the single-breaker design that followed for all other newer transformers.
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Thank you. Interesting to be sure. Is there a schematic for the transformer on the net somewhere? After perhaps 80 years the wiring looks decent in there. Not crumbling or cracking.
Wow. Who would have thought.
Rob, thanks for the explanation! I was wondering about the center tap, and this certainly explains why Lionel set it up how they did. Too bad Lionel moved away from it, as it seems like a very useful feature to have separate breakers for multi-throttle transformers. I suppose that’s where external breakers come into the equation.
-El
There is a pictorial diagram, but not a schematic.
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Thanks, appreciate it.
Your’s is prettier! 
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I have another question. I once had a train transformer that had a whistle button. Can you explain how that worked? The whistle came from the train not the transformer and it seemed to increase the speed of the train when the button was pushed.
Thank you.
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It’s simple: the train has a special relay that is activated by DC. When it receives this current, it turns on a motor hooked up to an air whistle in the tender. Some model diesels have a similar horn setup more like a doorbell. Anyway, the transformer would apply this DC to the track and therefore activate the whistle. This can actually be done with a D-cell battery instead (longer story). The reason the train sped up is because the DC increased the voltage and therefore the train could, of course, run faster.
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Lionel transformers have a “rectifier disc” inside that controls the whistle or horn. These late prewar and postwar “lettered” transformers had a “W” as part of their model/type designation. For example the two throttle Type R became the single throttle Type RW. T-TW, K-KW, Z-ZW. There were also numbered transformers like the 1033 and 1044 with a whistle control.
Early on in the prewar era Lionel sold separate whistle controllers that you wired between the track and transformer. In the postwar and MPC eras they still sold a whistle control button for operators using older power supplies. Lionel did have a whistle station that was part of their “Winner” line of IVES derived O27 trains, but most often the whistle was in the tender, or in the baggage car in the case of the postwar General.
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Depending how deep you want to go, there’s some nuance, but that’s pretty much it- DC makes the whistle turn on.
There have been some more in-depth threads on what makes the Lionel whistle go, but it boils down to the fact that Lionel trains run on Alternating Current, and Direct Current is used to trigger the whistle. Lionel developed a ‘shaded’ relay which, due to its design, will not close when its coil is energized with AC. However, if DC is passed through the coil, the contacts will close.
This section of the Lionel Service Manual talks a little bit more about exactly what happens, electrically, when the whistle control is operated:
the 5v auxiliary winding is what provides the ‘boost’ in power. The whistle tenders were powered by their own motor, which increased the load on the transformer when operating- I believe the idea was for the auxiliary winding to help compensate for the increased load, to reduce issues with the train slowing down when the whistle is operating.
The diesel and electric models (with exception of the prewar streamliners that had whistles, and postwar 2332 GG-1 with a coil and plastic resonating chamber) used a horn that was near identical to a type of bicycle horn marketed by the Delta Electric Company. I’ve seen pictures of some Lionel horns that Delta must have supplied, as they are marked Delta. These horns are powered by a 1.5v D cell battery, rather than track power. As a result, the diesels and electrics with these horns tend to run faster when the horn is activated since the track voltage is increased by the auxiliary winding, but there is not an increase in current draw.
-El
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Thanks to all.
I kinda thought it was DC but I don’t understand how the polarity of the DC was handled by the engine. The engine is capable of running on DC so isn’t it sensitive to polarity concerning what direction it is rotating.?
Thanks.