I have brought several of my 'dead-whistle' postwar tenders back to life by fully disassembling and methodically cleaning everything and then re-wiring, lubricating, and testing them. 671W, 2671W, 6466W, 2046W, 2426W, 6026W
With my Postwar ZW (Kent Schwartz refurbed) transformer - the rebuilt tenders whistle every time just like you would expect them to - albeit with that inescapable and familiar Postwar armature rattle/whine. With the 1999 modern-ish ZW using both a 180w brick or a 135w brick the whistle relay starts to chatter/cricket a bit, when voltage increases past 8~10 volts - and occasionally the whistle will sound above 12~14 volts. When the Whistle switch is pushed on the 1999 ZW the 'chatter' changes/intensifies, but it usually doesn't fire the whistle relay to sound. The Bell button on the 1999 ZW fires it every time and it will usually latch, sometimes permanently - or at least until I reduce the output several volts.
TESTING:
* My voltmeter finds roughly 0.2~0.5 volts of continuous DC on the A-U & D-U outputs of the 1999 ZW - but only a trace (0.009~0.01) of DC on the A-U & D-U outputs of the Postwar ZW.
* At typical conventional track voltage (9~10 volts) my voltmeter finds roughly (+) or (-) 2~3 volts of continuous AC boost/cut when the Bell or Whistle is applied and (+) or (-) 2~3 volts of continuous DC on the A-U & D-U outputs of the 1999 ZW when the Bell or Whistle is applied.
* At typical conventional track voltage (9~10 volts) my voltmeter finds roughly (+) or (-) 3.5~4.5 volts of momentary AC boost/cut when the Whistle is applied and (+) or (-) 2~3 volts of momentary DC on the A-U & D-U outputs of the Postwar ZW when the Whistle is applied.
Any guesses?
