ZW Whistle Diode

You would install a stud diode to replace the rectifier disc for the whistle. And you would install TVS across each binding post from positive to negative. They are non-directional diodes.

Do a search on TVS and you will see a lot about what they do.

You can replace the old copper rectifier disc with a stud diodes for whistle performance. A good resource for that procedure is here:

http://www.tranz4mr.com/ZW_Whistle_Diodes.html

The other diodes you are talking about are TVS diodes.

The TVS diode protects against voltage spikes caused by collapsing electromagnetic fields generated by the layout (relays, solenoids, motors, derailments etc).

A short video about those spikes:

Since the source is layout side, you want the protection layout side. Many people put them on the track, others put them on the output terminals of the transformer, and some do both!

With a ZW, it is easy to take 4 TVS diodes, shape them like this so they wrap around the binding posts, (A-U, B-U, C-U, D-U).

For our trains we recommend two models of TVS:

For power supplies in excess of 18VAC, such as your ZW, use the 1.5KE36Ca diodes.

For supplies that max out at 18VAC, then you could get by with 1.5KE33Ca diodes. 

They can be found on Mouser, DigiKey and similar electronics providers as well as the 'bay.

Wow, I wasn’t expecting this great website about the ZW’s. Thanks a million for this and the info. Wow... this forum is the best. Even thinking about subscribing to the magazine.