The power pick ups of the Bachmann Brill trolley assembly need to be isolated from the brush assembly for this DCC concept to gain traction, as the pancake motor is fed by contact prongs that touch either of the two halves of the motor bogie. (This unreliable method of electrical transfer has led to many a premature 'death' of a Bachmann Brill trolley).
My method of fitting DCC to these dinosaurs is to disassemble the pancake, remove/isolate the prongs and direct solder the orange/grey wires to the brush assembly, and connect the red/black wires in parallel to either side of the motor bogie and to the non driven bogie. It ain't pretty, but it works.
With the DCC conversion of the two Cooee Collectable RTR W class (964 & 812), the installation and programing of the decoders was easy, being can motors and smooth running at low speed; however the Bachmann Mechs (800 & 870) are completely different. Not only is the wiring unique, but all the phaffing around required when sorting through the CVs, for they can need a good kick in the arse to get going, then need a subtle touch on the throttle to stop them racing off at breakneck speed.
The other issue with installing decoders in the Bachmann Mech W class is the amount of real estate these units take up inside of the saloon, even more so when installing the lighting options as well. The W5 800 with its open three door drop centre section, per side, full of punters, really set the mind thinking of how to install a decoder, offer directional lighting and saloon lighting, all with one end of the car taken up by a pancake motor bogie...... (in the end, I think I may have nailed it.)
W5 800 (Bachmann Mech with NCE D13SRJ Decoder)
The underside of W5 800
So that's what I have been up to lately.
From under (amongst) the wires.