Add whistle control?

Sure.  Here is a 5906 Sound Activation Button that will work.

There are others too, K-Line made a nice one with a switch to select whistle or bell.  They turn up at dealers with NOS and on eBay.

You can make your own with some diodes

Described here

 http://www.jcstudiosinc.com/Bl...=412&categoryId=

Dale H

Here's one I knocked together in a small utility box.  It has both whistle and bell capability.  You only need SPST push-button switches, but what you see is what my junkbox had handy.

John what would I need for just the bell button?

Half the diodes and 1 less button. If you're going through the trouble of making one you might as well make the whole thing. The parts aren't that much.

Ron

Ron is right.  As you can see, this handles both whistles and bells.  Each string of diodes handles one function, the fact that they're reversed is what generates the positive and negative voltage to trigger the respective functions.

The thing with the diode string is that it has a substantial constant voltage drop and generates some heat because all of your train power goes through all the diodes, except when you blow the whistle. Use 6 amp diodes! I built one myself but switched to something else.

An old Lionel 147 whistle controller is super-simple; it just switches a D-battery into the track power momentarily to blow the whistle. Some guys don't like the idea of a DC battery in an AC circuit but this is what Lionel offered for an inexpensive add-on whistle controller, and it works. Has anyone had one blow up?

You don't have to replace the diodes like a battery.

I got one of the k line off ebay and it works great with the kw-190. Only thing is you need two of them.

Does your KW-190 with replaced diode blow other whistles? Any different if you reverse wires to the track? I'm wondering if there is some reason why a Williams train wouldn't respond to a typical Lionel transformer whistle control.

The Lionel 6-5906 sound activation button seems to be the easiest solution. Just wire the button in series with the power terminal of your transformer. I have a postwar ZW and I can't activate the bell. I am going to try this myself.

http://www.lionel.com/media/se...ents/73-6847-250.pdf

It's possible that the Williams locomotives aren't receiving enough voltage for the sound boards to function. I've noticed that Williams bell/whistle sounds don't operate very well at low speeds.

I second Nicole's observaton about Williams and low speed activation of bell/horn.  I have wired my William's motors in series, also in series with diodes to drop the voltage and also a thermistor.  Now the bell and whistle fire reliably at low speeds.  

I don't miss the top end speed reduction at all.  Very nice slow speed control.

I'm supposing that the Williams locos typically have DC motors which run fast on low voltages, so this is the real issue for the original poster - the loco needs to get a higher voltage for the whistle to work, not just a different whistle controller. A heavier train might make some difference too?