There were 3 different boards used in the LGB Mogul.
Oldest was the 2 boards in the tender with the awfull analog sound.
Next is the 25192 with the single tender board with super caps. My diagram shows this board in the 25192.
Lastly is the SUSI board in the engine under the metal plate in the firebox.
The first 2 had a rear engine sensor for the chuff with a 3 wire cable to the tender. If any of these 3 wires break then no chuff and bell and whistle usually do not work. This is a very common issue with the moguls.
So, the 6 pin cable going into the tender has 3 wires for chuff (+, -, and sensor output) plus the other 3 (2 for track power, one for tender light).