bmoran4 posted:Nope - just use TVS Diodes as prescribed all over this forum.
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 power supplies in excess of 18VAC, such as your ZW, use the 1.5KE36Ca diodes.
If you only use supplies that are limited to 18 VAC then you could get by with 1.5KE33Ca diodes.
Thank you Bruce, your comments along with the PBS video made perfect sense and an easy learning session. I learned about this very topic from the world's best physics professor, Dr. Prucha at Wis State Univ - Whitewater, way back when I was a young'n! Sadly, he is no longer with us, but his legacy is about a man wwho loved to get up in the morning, get dressed up into a suit and tie, and go teach physics to a bunch of kids, and he had a smile the whole time as he spoke with his slight Polish accent.
Sorry for the digression, sometimes peeps just want to share a very good memory 
Back on topic - I like to parallel a pair of tvs diodes wherever possible because a) they're cheap, and 2) that offers an increased level of protection against the rare open tvs diode, plus 3) I believe it might offer better current handling to prevent the catastrophic (to the diode) shorting failure. Sooo much cheaper than a new board!
