The Bachmann S4 is a fine running locomotive and requires no chassis disassembly for this installation.
The decoder install is quite easy and the biggest challenge was fitting a speaker into the cab.
Remove the couplers and gently pry the shell up and off of the cast metal chassis.
Clip the four black track pickup wires and the red and blue motor leads at the decoder. Remove the two small screws and remove the stock decoder.
Trim the four round nubs (two of which the decoder was screwed to) on the plastic motor hold down flush with the top of the metal chassis weights.
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Insulate the top of the metal weights with kapton tape. This provides a flat surface for the new Loksound 73100.
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I used 0603 SMD LEDs with magnet wire for lighting. Before taping the decoder down, solder the magnet wire leads to the light pads on which will be the underside of the decoder. Watch that polarity is correct. Resistors are already present on the decoder so no additional resistors are required.
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The track pickup wires and the motor leads fall nicely in place to be soldered on their respective pads. The speaker wires were also soldered to their pads.
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I used a Soberton 8x12 speaker and fashioned an enclosure from .020 styrene. The sides were shaped to fit the contour of the cab roof which will act as the roof of the enclosure.
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The fit is extremely tight front to back in the cab requiring the glazing pieces to be sanded thinner. This only affects the back flanges and not the part that protrudes into the window opening. The sides of the speaker enclosure were sanded a bit thinner as well.
The rear glazing piece was cut into two parts to provide a channel for the cab light wiring and the LED was glued into the opening.
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Once Everything was slimmed down, the enclosure was sprat painted black, pushed into the cab against the roof and sealed from the inside with Gallery Glass. Test fit the cab and shell to make sure there is adequate room between the front edge of the enclosure above the decoder for the speaker wires. The rear edge of the hood shell under the windshield needed to be filed some so it didn’t protrude into the cab which is now occupied but the speaker enclosure.
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The speaker was mounted facing into the enclosure in order to allow the speaker wires a good path up to the decoder.
I had never installed one this direction but it didn’t seem to make any difference as it puts out plenty of volume.
The speaker was sealed in using Gallery Glass.
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The front LED was glued into the headlight opening and all the wiring tucked above the mech and the shell set back on.
There was a lot of fiddling to get everything in the cab and the shell to seat properly but it all fit.
I didn’t install any caps as there wasn’t much room left but the pickup on this engine is pretty solid and seems to run fine without them.
I used Select Factory sound file 73891 which is actually for an Alco S5 but I wanted this engine to sound differently than my stock Atlas S2.
I changed the couplers to Z scale by trimming the coupler post flush with the top of the opening and putting the stock screw through the coupler and back in the original hole.
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Edit: After watching the video, I went back in and trimmed a bit off the front of the speaker enclosure and the cab seats down properly now.
