Sorting out the lights of a Network Rail Bachmann Class 57/3 locomotive



This page describes how the missing front marker lights and night headlight can be added to the Class 57/3 Bachmann locomotive. A Zimo MX644D decoder is used, providing a sound system in addition to a large number of function outputs.

(If an ESU LokSound decoder had been used instead, an additional function decoder would also have been required.) 

Class 57/3 in Network Rail livery.


The Original Bachmann Running lights:

The forward lights on the model are limited to the day running headlight on the right hand side, and the top marker light. Twin rear lights provide the correct tail end lighting. Cab lights are also provided.

Forward Lighting As Produced by Bachmann


Running lights fitted to the real Class 57/3 locomotives:

The real Class 57/3 locomotives also have white lower front marker lights. These use LED technology and take the form of dual function white marker lights or red rear lights. At the forward end, both the lower and top marker lights are displayed during day and night operations and should look something like this......

During night operations, the real locomotives use a headlight on the left hand side of the locomotive which is optimised for operation at night. Either the day or the night headlight is used, the right and left headlights never operate together. 


How Bachmann have arranged the lighting system in their 57/3 locomotive:

The upper body shell is fitted with clear plastic lenses at each end:

Inside the upper body shell, with the cab assembly & top PCB removed


In the cab roof is a small PCB assembly, which carries two LEDs. One is the top marker light and the other is an internal cab light. The marker light series resistor is also mounted on this board, while the series resistor for each cab light can be found on the main PCB (Resistor numbers R11 and R12).  Electrical feeds are via three flexible contact tabs.

Cab Roof PCB


The contact tabs, at the rear of the re-assembled cab assembly.


The chassis assembly carries lighting PCB assemblies at each end, a main PCB in the centre and two small contact pad PCBs to provide the electrical feeds for the upper body shell lighting PCBs:

Showing the PCB distribution on the chassis assembly


The lighting PCB is fitted with a plastic shroud to confine the light to the appropriate lens. The lighting PCB carries three leaded LEDs. The two inner tower style LEDs (fitted with sleeve covers) are the red rear lights, while the single outer LED is a white tower LED acting as the headlight. The PCB also carries surface mount series 1k5 resistors for all three LEDs and small value RF capacitors (not needed for DCC operation).  Four wires connect each lighting PCB assembly back to the main PCB.

The bogie needs to be unscrewed & moved to one side to remove the screw holding the lighting assembly to the chassis

(Don't forget to re-engage the drive shaft into the motor receptacle when refitting the I did :-)


Underside view of the Lighting PCB assembly, lifted away from the chassis.


Just behind the Lighting PCB assembly is a small rectangular PCB fitted with three pads on which the tabs of the Cab Roof PCB make contact.  Three wires connect the small PCB to the main PCB.

Contact pad PCB


The main PCB on the centre of the chassis assembly provides the interfacing for the lighting LEDs with the 21 pin DCC decoder.

Main PCB (Showing the 21 pin decoder connector with the blanking plate removed.)



The Original Lighting Circuit:




Lighting modifications Summary:

A new Zimo MX644D sound decoder and speaker are to be fitted to the locomotive. The Zimo decoder has a large number of function outputs available to enable the lighting to be controlled entirely by DCC console commands. The switches on the underside of the locomotive and their connections to the Main PCB, will therefore be removed.

A new night headlight and new lower white marker lights will be added to each Lighting PCB, plus replacement Rear lights. Additional connections will be made to the 21 pin connector on the Main PCB to facilitate access to the required Zimo function outputs. Some additional components and wiring will be fitted to enable the new lighting to be grouped for day running forward lights, night running forward lights, rear lights and cab light at each end of the locomotive.

The new Zimo "Swiss Mapping" system will be used to provide an easy control interface to the user.



The new Lighting Circuit:




The Updates in detail:

(Refer to the circuit diagram above to see the updated sections in context.)


1) Adding the night running headlight:

Bachmann have helpfully provided mounting facilities for a 2mm tower style leaded LED in the night headlight location. Less helpfully, their PCB tracking assumes the night headlight comes on at the same time as the day headlight, but as long as the missing surface mount series resistor is left unfitted, an independent negative connection can be provided by adding an extra wire to the PCB, routing via a new series resistor mounted on a new plasticard assembly, to the main board.  

Lights PCB Assembly, Front View.


Lights PCB Assembly, Rear View.


2) Adding the new lower marker lights and replacement rear lights:

There is not really enough room to add additional lower front marker lights, if the original Leaded rear light LEDs stay in place. So I removed the original rear light LEDs and replaced each with a small plasticard assembly, fitted with a new white chip LED (for the marker light) and a replacement red chip LED (for the rear light). The chip LEDs are mounted close together and a few mm behind the lens, so that either LED provides illumination through the lens. Rigid wires are fitted to the new assemblies and are connected to the chip rear light LEDs. The new white chip LED positive is connected to the rear light positive lead. The white LED negative is connected to a thin enamel coated wire which is routed to emerge between the top edge of the lighting PCB and the plastic shroud, attached to the PCB. The rigid wires fit in the mounting holes for the original rear light LEDs.  The new chip LED assembly is shown below, mounted on a piece of Blue Tac.

New chip Rear light and marker light assembly replaces the original rear light LEDs



The first modified lighting PCB assembly


3) Fitting the extra diodes and series resistors:

A small piece of plasticard is used as an insulator, to mount most of the additional leaded components at each end, with just one resistor glued to the main PCB for convenience.

Number one end:

The parts on the plasticard sheet are covered by insulating tape to ensure that no contact is made to the nearby speaker contacts in the upper body shell

Number two end:

A hole in the number 2 end plasticard enables the bogie screw to be accessed


4) Updates to the Main PCB:



a) Just one track cut: The top track between R11 and R12.

b) Add extra wires to the 21 pin connector to access the Zimo decoder FO3, FO4, FO5 and FO6 as shown in blue above.

c) NB: Change of plan.....The Link across the Bachmann series resistor R16 was not in fact fitted!

d) Some of the wires attached at each end of the PCB are re-routed, so need to be cut close to the PCB: Specifically, the Orange, Green and Brown wires.

e) The underside switches are disconnected and removed, as DCC commands will now control the lighting. Remove the wires from the clips at the two S1 tab connections and the two S2 tab connections (marked *).



Quick Zimo Decoder Programming to test the lights:

The Zimo MX644D decoder on board has a sound project installed that uses most of the function buttons above zero and below 12 for sound purposes. Before detailed re-mapping of the buttons, it was convenient to use function button zero, with a CV change, to switch between night and day operation during the test:

1) Check CV61=97..... yes.

2) Set CV33 = 1 + 32 (H/L + FO4) = 33 for day running test

3) Set CV33 = 4 + 32 (FO1 + FO4) = 36 for night running test

4) Set CV34 = 2 + 16 (R/L + FO3) = 18 for day running test

4) Set CV34 = 8 + 16 (FO2 + FO3) = 24 for night running test



The Updated Lights:

Showing the revised running lights in action at end 1 (the first completed end):

Day running Lights (including lower marker lights)

Night running Lights (including lower marker lights)

Showing the rear lights active at the same end



Zimo  Conventional Function Remapping :

The cab lights are assigned to button 8 and made directional (only the forward end cab light comes on):

CV42 set to FO5 + FO6 = 64 + 128 = 192

CV131 set for FO5 forward only = 1

CV132 set for FO6 reverse only = 2


Zimo Swiss Mapping:

Button 0 day running light engine (Right hand headlights in use, directional lights both ends).

Button 0 + 20 day running end 1 only (Kills rear lights at end 2 if towing a train and switches end 1 lights from front to rear lights when backing up the train).

Button 0 + 21 day running end 2 only (Kills front lights if banking or kills rear lights if towing a train with the number two end leading.)

Button 0 + 22 night running light engine (Left hand headlights in use, directional lights both ends).

Button 0 + 23 night running end 1 only (Kills rear lights if towing a train and switches end 1 lights from front to rear lights when backing up the train)

Button 0 + 24 night running end 2 only (Kills front lights if banking or kills rear lights if towing a train with the number two end leading.)              





0 (F)

Fwd Outputs



0 (R)

Rev Outputs




Button F (20)




Button M  (0)




1st Fwd O/P (FO-H/L)




2nd Fwd O/P




1st Rev O/P (FO3)




2nd Rev O/P




Button F  (21)




Button M  (0)




1st Fwd O/P (FO4)




2nd Fwd O/P




1st Rev O/P (FO-R/L)




2nd Rev O/P




Button F  (22)




Button M  (0)




1st Fwd O/P (FO1)




2nd Fwd O/P (FO4)




1st Rev O/P (FO2)




2nd Rev O/P (FO3)




Button F  (23)

448 23

Button M  (0)

449 157

1st Fwd O/P (FO1 )

450 1

2nd Fwd O/P

451 0

1st Rev O/P (FO3)

452 3

2nd Rev O/P

453 0

Button F  (24)

454 24

Button M  (0)

455 157

1st Fwd O/P (FO4)

456 4

2nd Fwd O/P

457 0

1st Rev O/P (FO2)

458 2

2nd Rev O/P

459 0


All working correctly!


Smooth running....... Some changes that transformed the operating feel of the loco:

The loco behaved well at extremely low speed and at medium to high speed. However, movement at around 1/4 full speed exhibited undesirable cyclic hesitation, where the speed "wobbled". Following the Zimo manual advice, I first tried CV9 which can be changed to modify the BEMF sampling characteristics. Three pole motors sometimes benefit from a change to the value 87, but this did not fix the problem. Next recommendation was to alter the drive frequency from 20kHz to 40kHz. This is controlled by CV112. Changing from the zero default to a value 32 changes the motor drive to 40kHz. This change immediately solved the problem, with the locomotive now performing smoothly throughout its speed range..... or at least as much of it as I could explore on the small test track!


Number Two End Running Lights Photos:

Day Headlight

Night Headlight


Rear Lights



Cab lights Photos:

Switched on via controller button 8. Only the forward cab light illuminates.

Number two end (unmanned) cab light on

Number one end cab light on



Adding the missing lower marker lights has a very positive effect on the appearance of the forward end of the locomotive.

The camera does exaggerate the intensity of the running lights, but the brightness levels may still be a little on the high side......  The series resistor values could be somewhat increased to reduce the LED brightness if this is preferred.

The chip LED assemblies were quite fiddly to make and to fit, with a few repairs needed during the course of construction. 

The Zimo decoder has a large number of available function outputs, which provides plenty of flexibility to handle different lighting combinations without the need for external circuitry. The "Swiss mapping" facility enables specific combinations of different lights to be selected via single button presses.


Supplier website links:


Digitrains    Helpful source for pre-wired chip LEDs.
Zimo Website    For access to the 2013 user manual
Rapid Electronics of Colchester    A good reasonably priced source for electronic components.


The photos of the model were taken using a hand held Canon Ixus 220.    


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