The first four of my Bachmann Spectrums to be decoder-equipped were done by Glynn Chamberlain, who did the installation more or less in the manner as set out below.
Unfortunately, when I did these installations, I did not yet possess a digital camera, so you will not have the benefit of pictures while following this guide. And since I've sold all my Bachmanns some time ago, taking pictures now is not possible. Let's hope my word pictures are clear enough!
I used the Digitrax DN147A (since replaced by the DN163A1) decoder in these locos. The Lenz LE062XF equivalent should work just as well.
One has to make room for the decoder by discarding the loco's original light PCB and by milling away about 1.5 to 2 millimetres off the top of the whole frame, and somewhat more (about another 1.5 to 2 mm) ahead of the cut-out bit of the frame at the rear end, up to above the middle of the rear flywheel cavity. This will still leave 1 mm or more of the frame above the motor cavity and will therefore not weaken the frame more than necessary.
Some milling in the motor cavity is also needed to isolate the motor brush caps from the frame halves. Just sticking a piece of tape in there for insulation is not a good idea since over time the brush caps may cut through the tape and cause a short.
IMPORTANT: Remember that ALL components have to be removed from the frame halves before milling, even the plastic spacers that keep the frame halves separated, since these may melt when the frame heats up while being milled. Also be very careful when clamping the frame, to prevent any bending or distortion of the frame. Do the motor cavity milling first, while the rest of the frame is still intact and therefore stronger.
One also has to make a plan to attach the decoder's power pickup tabs to the frame, since one cannot solder to the frame itself. I do that by drilling a small hole in each frame half from above, in the solid part of the frame between the rear flywheel cavity and the rear worm gear, into which a very small screw can fit tightly. The wire connections to the decoder's power pickup pads can then be soldered to the screw heads.
Another option is the method that Glynn Chamberlain used when he installed my first decoders in Spectrums, namely to wrap the power pickup wires around one of the screws that hold the two frame halves together, one wire each side. Both methods work very well.
The gap between the frame halves above the motor cavity is normally ample to pass the motor wires through, but if necessary it can be enlarged slightly just above the brush caps.
After finishing with the milling of the frame and cleaning the frame halves thoroughly of all metal fragments, I normally attach the motor wires to the brush caps and then completely reassemble the loco frame, motor, drive train, wheels and all, before soldering any wires to the decoder. Assemble the frame with the two wires from the motor brush caps sticking out at the top through the gap between the frame halves.
One then has to apply insulation tape to the whole frame top to prevent decoder components from shorting out on the frame. I install the decoder upside down, to make it easier to attach the wires from the motor brushes to the decoder's motor pads. The decoder just lies loose on top of the frame, with its front LED resting in the little light cavity at the front end of the frame top, and it is held in position by the shell once the loco is completely assembled.
For the C40-8W only, the decoder's front LED has to be unsoldered and refitted on two ½ inch pieces of stiff wire that can be bent in such a way that the LED sits just above the front worm gear, otherwise the front light lights up the cab windows instead of the headlights.
If anything about the procedure is perhaps still unclear, or if you used this guide and it worked for you, please drop me a note.
Good luck, and keep them on track!
The following pages contain decoder installation guides for some other N scale diesel locomotives:
And the following pages contain guides to servicing or performance enhancement of some N Scale diesel locomotives:
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Created in January 2001. Last updated on 11 September 2003.