Installing DCC decoders in a Bachmann Class 158 DMU

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Last updated 2 July, 2014
Class 158

 

Before installing chip into any loco it is advisable to check the current being drawn by the loco. You should test the current drawn when the loco is stalled to find the peak current and select a decoder that will cope with that maximum current requirement.

There is no decoder socket in this model so it is necessary to hard wire in the decoders. This is not difficult for a modeller with some basic soldering skills.

For this installation two decoders were used, a wires only TCS MC2 in the power car and a lighting only TCS FL2 in the trailer car.

 

Class 158

On the Bachmann Class 158 there are 2 screws securing the body to the chassis. There is one each end located under the bogies - just move the bogies to one side and they become clearly visible.

Once the screws have been released the body comes away from the chassis by gently levering the body by sliding finger nails between the body and chassis.

Class 158

When removing the body be careful as there is a cable connecting the body shell to chassis. This connects the power for the lighting and should be disconnected by pulling the connector apart.

Class 158

 

Remove the black tape over the motor assembly and put on one side for use again later.

Desolder the connections fixing the capacitors in place and discard them. Slide the heatshrink away from the resistors, desolder the connections to the wires and discard the resistors.

 

Class 158

 

Put a piece of heatshrink on the red wire from the decoder then solder it to the two red pickup wires coming from the chassis. DO REMEMBER TO PUT THE HEATSHRINK ON BEFORE SOLDERING THEM TOGETHER!! Solder the orange wire from the decoder to the motor terminal on the same side of the chassis as the red wires.

Now repeat the process on the other side of the motor, soldering the black wire from the decoder to the black pickup wires and protecting the joint with heatshrink. Solder the grey wire from the decoder to the motor terminal on the same side of the chassis as the black pickup wires.

Fix the decoder on top of the motor with a sticky fixer pad. If the decoder you install is not protected with any form of insulation it would be advisable to do so before fixing the decoder in position. All wired TCS decoders are already insulated.

 

Class 158

 

With the motor connections complete it is now necessary to turn to the lighting control.

At the front of the power car is a small circuit board that controls the DC lighting. It is held in place on two lugs that form part of the chassis casting. Gently lever the board away from the lugs with a flat headed screwdriver.

On top of the casting is a screw holding the bogie assembly in place. Undo this screw and let the bogie drop down.

 

 

Class 158

 

 

The black and red wires from the lighting board need to be disconnected from the track power. Trace the route of each wire to the pickup on the bogie and cut the wire as close to the pickup as possible. MAKE SURE YOU CUT THE RIGHT WIRE AS YOU WILL NEED THE OTHER PICKUP SOURCE FOR THE MOTOR POWER!! Make sure there are no exposed strands from the wires you have cut that could produce a short circuit.

 

 

 

Class 158

Desolder the other ends of the short red and black wires from the small circuit board.

Then solder the white, yellow and blue wires as shown in the photo alongside (left). A small piece of blue wire should be soldered to bridge the two connections on the motor side of the board.

Now reconnect the lighting cable between the light board and the body and test the power car motor control and lighting on F0 to make sure it works correctly. If all is OK tidy the decoder wires and replace the black tape over the motor and decoder. Replace the body making sure you start from the driving end by locating the coupling through the hole in the body.

Class 158

 

Now for the lighting in the trailer car. This works on the same principles as the power car. It would be possible to extend the wiring from the decoder in the power car into the trailer car, but this is very messy and involves cutting parts of the body and installing plugs and sockets and/or having trailing wires.

A separate decoder in the trailer car provides, at least to my mind, a much neater solution, if a little more costly (though quicker in terms of time and potential damage to the model(s)).

Remove the body in the same way as for the power car and disconnect the lighting connector between body and chassis.

 

Class 158

There is a lighting board at the end of the trailer car.

Desolder the red and black pickup wires from the circuit board and connect these to the red and black wires from the decoder, using heatshrink to provide insulation.

DO NOT DISCONNECT THE WIRES FROM THE PICKUPS!! These provide the power from the track to the lights via the decoder.

Wiring colours on the TCS FL2 decoder do not follow the same colour convention as that for motor decoders, so the green wire is equivalent to white and the purple wire is equivalent to the yellow wire. Solder the green and purple wires from the decoder to the circuit board as shown in the photo (left). Make a similar connection with the blue wire to that made in the power car.

Reconnect the lighting plug between chassis and body.

Place BOTH units on the programming track.

In order to get the FL2 to act automatically using F0 as the lighting control it is necessary to alter the CVs shown in the table below to the specified settings.

CV

VALUE

51

0

52

16

35

1

36

2

Program the loco number as required and both units should operate as one, as both decoders will have the same loco address.

If you want to change which function buttons operate the lights then you will need to consult the TCS decoder documentation. Further modifications are possible to the lighting which enable you to operate individual lights, but this is beyond the scope of this guide.

Refit the body and away you go......!!

 

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