Perplexing ZW / Steam Loco Whistle problem

The modern engine isn't drawing enough current through the ZW rectifier to produce a strong DC offset.

Thanks!  So does that mean the modern transformers are less "resistive" (not sure what the correct term would be) and therefore it's easier for the loco to draw the current for the whistle?

@LarryM2 posted:

...does that mean the modern transformers are less "resistive" ...

Well, no, the output on the CW80 is regulated by modifying the sine wave - modulation/shifting/pulse width - so the scheme is very different - it's done electronically by biasing the AC wave with a plus(horn/whistle) or minus(bell) offset - easily seen on a scope.  As you approach full throttle on the CW, you will notice that the DC bias becomes weaker as there is less "overhead" to work with within the 17.9 volt maximum output of the transformer.

Had the same problem with my williams switcher. Changed the older zw rectifiers to modern solid state devices and it fixed the issue.
I do have to swap the common and power terminals to change from horn to bell.

@JJH posted:

...I do have to swap the common and power terminals to change from horn to bell.