I found an error in the Lionel Pinout diagram for RS 4.0 Modular board. The Hall effect sensor output pins 19 and 23 are reversed. Pin 19 is +5VDC out and pin 23 is AC ground reference for the sensor. The attached file is the orig lionel document and is incorrect.
Also for the early Lionel steam using tender Hall effect sensors for chuff with Railsounds 1 the color code is Green wire +5V, Yellow Ground, and Blue Trigger.
I successfully used the Hall effect sensor as the chuff trigger for RS 4.0 upgrade to the tender. Vice using a reed switch.
Some of these early steam engines where the Mechanical E unit, pullmore motor engines of the 6-180xx models. G