When operating my post war trains with my ZW transformer, is it common occurrence for the train speed to drop when the whistle is operated via the whistle/direction lever? Is there a way to avoid this? Thanks in advance, Martin
There is an extra 5-volt secondary winding that the transformer’s whistle control switches in when you blow the whistle. This is meant to compensate for the voltage loss due to the rectifier that is also switched in to introduce a DC component into the track voltage, as well as for the additional load of the whistle motor. This compensation is obviously not exact and might under- or overcompensate according to the locomotive type, train load, speed, and so on. This may be what you are experiencing.
However, there is another possibility. As you move the lever, it first switches in the extra winding and the rectifier. As you move it farther, it shunts the rectifier with a resistor, which is meant to restore most of the AC voltage and decrease the DC component to just enough to keep the whistle relay operated. It may be that that part of the switch or the resistor is faulty, or that you are not moving the lever far enough. My experience is that most trains will speed up when the control goes to that second position. As you move the lever, see whether you can observe the two steps of operation that I have described.