Hi C.W.!
Thank you for the instructions on how to adjust the breakers, I'm going to try that out later today (after the kid's soccer games!).
I've been assuming that the rectifier disks are bad because the whistles on my engines are not working when I try them with the ZW, but they do work when I use my CW-80s. I'll remove the cover again later as well and check the contacts for the whistle switches, it seems odd that both would have issues, which is why originally I thought perhaps I was doing something wrong.
I'm going to pick up a few more of the #91s from "the bay" this week to (I think), but don't tell anyone because I don't want to get in a bidding war ;-)
All the best and I'll update later today if I can.
Thanks again...Rich