lionel LW 125 question

[djrmmr]

My question pertains to the whistle button on the LW 125. I note that when pushed half way down, the whistle works but continue to push and the whistle stops and there is a power surge to the engine. What's up with that???

[lionelsoni]

In the half-way position, the control inserts an extra 5-volt winding and a (copper oxide) diode in series with the normal transformer winding, changing the waveform to half-wave DC to operate the whistle relay, which is more or less insensitive to AC.  In the full-on position the control puts a resistor in parallel with the diode, allowing much of the AC waveform to be restored, reducing the DC component, but leaving enough to keep the relay operated.

It seems that, in your case, your train is drawing little enough current that the resistor is too effective, restoring more AC than intended and leaving too little DC to keep the relay operated.  Are you perhaps using a modern locomotive that might draw less current than the transformer is designed for?  An older Diesel locomotive could also produce your symptoms, since it lacks the extra load of the whistle motor.

[TrainLarry]

The speeding up of the locomotive is normal. As Bob states, there is an extra 5 volts added to the track when the whistle button is pressed all the way down. This is because the motor driven whistles require extra power to operate, and without the boost, the train would slow down, as you see when you press the whistle button half way down.

If the whistle stops when you press the whistle button all the way down, you may need to add more cars to the train to load down the transformer a bit more. Sometimes with a light load, the transformer will not keep the whistles blowing constantly.

Both of these scenarios are normal for postwar transformers.

Larry