I was asked to post pix of the conversion of my 3rd Rail Niagara to ERR electronics. I have only one picture available at the moment:
I'm don't like the boards being located as far aft on the tender as they are. Their position was driven by the need to be able to remove the 9V battery. Locating the sound board so far aft caused tether length issues. I had to drill the drawbar to pull locomotive and tender closer together in order to ensure a reliable tether connection. With my mainline curves at O104 and higher, tightening that spacing didn't present any operational issue - and certainly improved the looks of the set. In retrospect, perhaps it would be better to mount the sound board atop the battery's U-bracket, using double-sided tape. The Cruise Commander board would still need to be where it is and the tether leads would still need to reach its rear. If the 9V battery is omitted or its bracket moved to the aft end of the tender, the tether situation improves significantly.
One of the minor issues that needed to be handled was the TAS smoke fan scheme. The TAS Niagara took 5V from the Lionel Railsounds power board to power the TAS fan driver board located at the front of the locomotive, via the tether. I put in a new Sunset/3rd Rail smoke unit (from Royz Trains), which has the fan control onboard and doesn't need an external 5V power source. After doing that, I realized that the 5V for the TAS fan controller could have been obtained from the original Lionel smoke unit, which has a 5V output jack.
I also had to fabricate a mounting arm for the reed switch that senses the disc magnet on the leading fixed tender wheel.