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Converting the BCH Minitrains Plymouth to DCC

Described here is how I converted a BCH Plymouth to DCC. The goal was to avoid drilling and milling, and still keep the shell and chassis as separate parts without any disturbing wires between the lamp circuit in the ceiling and the chassis.

Please keep in mind that this will probably void the warranty of both the loco and the decoder.

First preparation was to fix the brass wipers on the inside of the cab with CA, then they were tapered a bit to avoid the strips to bend when you put the shell on the chassis.

Next is to find a place for the decoder. I used a Digitrax DZ125 which was a perfect fit in the “pocket” on the side of the cab after some trimming. You will need to cut off some of the shrink tube in both ends for a good fit.
Be careful so you don’t cut the wires or PCB.

You could also remove the shrink tube completely, but that would make the decoder more fragile.

The decoder was glued with contact cement to the chassis, and allowed to dry.

Maybe the worst part is to isolate the motor from the chassis.

It can be lifted out by inserting a small screwdriver at the rear end and carefully jacking the motor up. You may have to do this from both ends of the motor. Be very careful as the clips in the chassis can easily break. This applies when reinserting the motor too.

The gray and orange leads were cut to length, and a small length of shrink tube was entered on the leads.
Note that the grey wire goes to the bottom side of the motor.

Then the tabs on the motor were twisted in position, and the leads were soldered to the tabs. Finally the heat shrink tubes were put in place and carefully warmed up a bit with the soldering iron. Do not use a lighter or torch, as you could melt parts of the motor.

Before replacing the motor, the lower connection should be flattened a bit with a small plier to make room for the extra wire. You could also skip the heat shrink tube and use some isolating tape instead.

Then carefully replace the motor, this is best done after removing the capacitor located under the white tape at the front of the cassis. Be careful so you don’t break the clips, and check the motor and clips for proper alignment after it is seated.

You may have to adjust the motor a bit from side to side so that the gray wire is not making the motor to cause any binding.

Next comes the pickup for the decoder. I chose to use the same method that is originally used for the headlight.
I glued some 0.1mm brass pickups at the rear end of the chassis that were soldered to the black and red wires from the decoder.

Make a slight bump on the pickups so there is proper contact when the cab is replaced.

Another method could be drilling and threading holes for screws in the chassis, but that would involve more tools.

Luckily the headlight accepts full voltage with any polarity, so the connection is simple without any resistor or polarity considerations.

For connections to the headlight, I first isolated the outer parts of the rear of the chassis with some electrical tape.
Then I soldered some thin strips of 0.05mm brass to the blue and white wires from the decoder.
The strips were then glued to the isolated parts of the chassis.

For now, the wires are a crow’s nest, but maybe some paint and glazing could do the trick. The wires could also be
shortened some more.

And finally, time for a break. Everything works smooth and quiet, and there is no noticeable humming from the motor, but it gets a bit warmer from the pwm signal.

Jorgen

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