Technical drawings and user manual can be found at the link below

https://drive.google.com/drive/folders/1EPFuNVNm1mDCpiNmdPkkZf2ZommkkNkz?usp=sharing

I created a Google Drive share location that contains the Heisler technical drawings and user's manual.

https://drive.google.com/drive/folders/1EPFuNVNm1mDCpiNmdPkkZf2ZommkkNkz?usp=sharing

The manual is ~11MB
The technical drawings are ~7MB

The 2-4-2 has an 8-pin DCC connector which controls motor and lights.  Sound is accessed using two solder pads on the main PCB.  The pre-wired speaker is already wired to the main PCB and the DCC decoder will need to be wired to the PCB.  You need to solder the sound output from the decoder directly to the PCB or make up your own cable with connectors.

https://www.bachmanntrains.com/home-usa/dwg/dwgs/LS%202-4-2%20(Connection%20Diagram).pdf

I used a small 1.5 amp DCC decoder (generally used with HO scale models) with sound in this locomotive and it works fine, but I don't intend to use this locomotive to pull any cars.  If you would like to pull more than a couple small cars, the 1.5 amp decoder would be undersized and likely let out the magic smoke.

It doesn't appear that Bachmann has the Large Scale Heisler technical drawings available at https://www.bachmanntrains.com/home-usa/references.php

I've scanned these pages from a #81799 Unpainted Unlettered Large Scale Heisler and can provide these pages to forum members as either a set of JPG images or a single PDF. 

If Bachmann would like a copy of the PDF to add to their technical library for owners to have access to, I can provide upon request.

I recently purchased a Bachmann 36 Ton two truck shay #81197 (six screws in bottom truck cover).  The locomotive runs fine and is fairly complete,  but it did not come with the users manual or the exploded parts diagram.  Does anyone have a PDF version of these documents which can be shared with the forum?  I'm specifically interested in the truck contacts with the intent that the locomotive will be converted to DCC which would require rewiring the trucks and providing an additional set of contacts between the trucks and the locomotive.    I am aware of the suggestions seen at

http://girr.org/girr/tips/tips1/shay_tips.html

but the approach taken by George Schreyer will need to be modified depending upon the limited availability of parts.  Specifically, Bachmann does not seem to have the Large Scale Shay

* bolster pcb ( https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=69_143&products_id=10507 )
* power pickup PCB ( https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=69_629&products_id=10374 )
* brass contacts
* etc.

in stock any longer.  

The locomotive did arrive with a VHS tape containing the lubrication and maintenance procedures for the locomotive.  I've converted this VHS tape to digital video and posted the video to YouTube.  https://www.youtube.com/watch?v=C6gWomcFk-4&t=29s  

I have not seen this video posted under the BachmannTrains youtube channel, but can send the video to Bachmann at their request and have them upload the video to their channel.