DCC conversion and Lighting update of the Hornby Class 153 single car D.U.

 

Introduction:

This page provides a summary of the process adopted to incorporate a DCC decoder and correctly operating external LED lighting in the Northern Rail variant of the Hornby single-car Class 153 unit (OO gauge).

Note that the smaller pictures can be enlarged by clicking on the image.

 

Northern Rail Class 153 (coupled to a Class 155 pair) at Leeds Station 09/09/09

 

A few Initial issues with the original Hornby Class 153 unit:

DC control: On the example I have, low speed control was virtually impossible to achieve, using my old Hornby rheostat controller. As soon as the speed control knob was moved off the stop position, in either direction, the 153 took off at quite moderate speed. (No doubt, a modern adjustable output voltage controller would achieve better results.) However I'm confident BEMF DCC control will be fine.

Lighting arrangements: The Hornby model includes a pair of headlights, marker lights and rear lights at each end of the car. However, analogue DC headlight operation only facilitates daylight running with the right hand headlight and both marker lights active at the forward end. The marker light intensity is far too bright when compared to the headlight.  During night running, on the real class 153, the left headlamp and both marker lights at the forward end of the car are used, but the Hornby lighting system does not support this mode of operation.

DCC Conversion Approach:

The plan is to use a 4 function and back emf motor controller TCS T4X decoder. To provide correct operation of day and night running lights, 4 function outputs and some additional transistor circuitry are required.

External Lighting Modifications:

It is planned to use the existing Hornby LEDs and light pipes for the marker lights and rear lights. New LEDs will be added for both right hand and left hand headlamps at both ends of the car. The DCC decoder programming and additional transistor circuitry will handle correct day and night running of the lights via function buttons 0 and 1 respectively.

 

Day running Lights

Rear Lights

 

Circuit Diagram for lighting: 

The original Hornby LEDs use a common negative supply. The PNP transistors are used to switch the common positive supply (blue decoder wire) to these LEDs under the control of the white and yellow decoder function output wires, which will provide directional control. The positive feeds to the new headlight LEDs are also controlled by the transistors, ensuring that only the forward end headlights can be activated. The negative ends of the headlight LEDs are switched via the green function wire for daylight operation (right hand side) and the purple function wire for night operation (left hand side). The resistors in series with each LED control the current flowing through that LED. This determines the intensity of the light generated by the LED. The above values were established by experiment, for the LED types employed. Some adjustment may be required if different LED types are used. The resistors in series with the headlight LED anodes were a convenient way of adjusting intensity variations between the two cabs.

 

Short and Long Cab Definition:

The Class 153 units began life as half of a two car Class 155 pair. They were then modified to serve low capacity lines, where a two car unit could not be justified. The modification mainly involved the installation of a very short (front to back) new driver's cab at the vestibule end of the original Class 155 unit. The new cab was so small, it is rumoured that the driver's union was concerned that only their smallest members would be able to drive the new Class 153 from the small cab end. On the Hornby model, the small cab end is adjacent to the motor bogie. It is fixed to the upper body shell and includes the lighting system for that end of the vehicle. 

Achieving Access to the car:

First the upper body shell must be separated from the wheeled chassis unit.  This is a difficult operation, as the mouldings fit very tightly together. The lower edges of the sides need to be gently eased outwards to release the plastic clips along each side of the car, allowing the two assemblies to be separated, starting at the short cab (motor) end.  The tricky part is opening an initial gap. I found that using a small screwdriver, inserted behind the motor bogie, pressing the side outwards with respect to the chassis, worked for me.

                                                   

Hornby advice

 

My technique to open the initial gap

 

Followed by card strips to open up the clips

Upper body shell, lower chassis and short cab

 

Access to the Lighting PCB Assemblies:

The short cab lighting assembly is clipped into the upper body assembly. Spring contacts provide the electrical supply to the two original LEDs in this assembly. The short cab and its light pipe assembly can be unclipped from the upper body shell. The long cab assembly is part of the chassis assembly, with its associated light pipes sandwiched between the cab and the end wall of the upper body shell.

 

Closer look at main PCB on chassis and short cab

Light pipe assembly in short cab end of upper body shell

 

Fitting the new LEDs:

To accommodate the new headlight LEDs, the light pipe housings and the clear light pipes need modification. First the dummy lens of the left hand headlights is removed. Next, the clear light pipes are modified to remove the original right hand headlight. This was accomplished using a fine tooth junior hacksaw and appropriate needle files. A picture showing the modified clear light pipe in its housing is shown below. (On the example shown, I over-did the notch for the new headlamp and had to cut some extra notches in the thinner part of the light pipe to rebalance the light levels from the marker lights.) I was more careful on the corresponding part from the other cab, and rebalancing was not required this time.  The light pipe housings then receive small slots to enable the bodies of the new tower LEDs to fit. The new LEDs are 2mm tower types, available from specialist suppliers such as DCC Supplies and/or Bromsgrove Models (see end of article for website links). Curiously, the headlights used in the long cab end are smaller that those used in the short cab. The cylindrical part of the LEDs used at the long cab end must therefore be carefully filed down to a new diameter of circa 1.5mm. (The short cab end accommodates unmodified 2mm LED parts). The internal cab assemblies are drilled to take the leads of the LEDs. The short cab front face must also be relieved to take the rear bodies of the new LEDs.

Modified clear light pipe in the light-pipe assembly, ready to receive the new headlight LEDs

Eliminating "Light bleed" between the new LEDs:

Light from the LEDs will couple into adjacent devices if fitted straight out of the bag, producing a very unrealistic effect. To prevent this, the LEDs are painted with gloss black modelling enamel, leaving just the outer face of the 2mm diameter tower exposed. I now also paint a white dot on the negative side of the LED body (shortest lead) before use, to avoid later wiring errors. Once the LED leads are trimmed, its easy to forget the polarity!   

Black painted LED beside "as delivered"

 

Fitting LEDs to front-piece:

The new headlight LEDs are pressed home into the light pipe housing, until their front face is flush with the existing rear light lenses.  The leads are then passed through the pre-drilled holes in the cab plastics and bent/trimmed for retention. The headlight series resistors are soldered to the appropriate leads and positioned vertically on the rear of the cab(s). 

 

Short cab with headlight LEDs fitted

Light pipe assembly added ready to clip back in place

 

I decided at this point, to separate the long cab assembly from the chassis seating moulding, and to mount it in the upper body shell, as this somewhat simplified the subsequent wiring and made the final re-assembly operation a little easier. I made some plasticard retaining blocks and glued these to the inner side of the upper body shell, to retain the long cab in position. The chassis side walls had to be trimmed back in the area of the long cab, to enable the top and bottom assemblies to fit together correctly.

Long cab fixed in upper body shell

 

  

Short Cab light fittings

Long Cab light fittings

 

Adding transistor circuit and control resistors:

The transistor and resistor circuitry (as shown in the circuit diagram above) are mounted in the form of a 2 dimensional classic "rat's nest", taking great care to avoid short circuits. An insulating tape cover is placed over the circuit. The original Hornby circuit board, above the motor on the chassis unit, is replaced by a plasticard sheet to support the new circuitry and keep it out of sight, above window level.

 

The original Hornby printed circuit board assembly

The new circuitry mounted on a plasticard sheet

 

 

Connect the T4X decoder:

The appropriate decoder wires (as shown in the circuit diagram) were then connected to the rats nest circuitry.  The decoder red and black wires were connected to the Hornby (black) track contact wires and the decoder orange and grey wires to the Hornby (blue) motor wires. The capacitor originally soldered directly to the motor contacts was carefully removed. Heat shrink sleeving was used to insulate the new wire joints. The decoder was fitted to the underside of the roof, just clear of the plasticard sheet supporting the circuitry, using a double sided adhesive foam pad. The chassis unit and upper body shell were then reunited to enable programming and testing. 

 

Decoder fitted in roof of upper body shell

 

Programming the CVs:

Using the DCC controller (mine is a Bachmann Dynamis) the CV values were programmed into the decoder.

CV Purpose

CV Number

Value

Lighting control

White wire (Forward short cab, reverse long cab) no dim

49

0

Yellow wire (reverse short cab, forward long cab) no dim

50

16

Green wire (daylight running HL, for+rev) no dim

51

32

Purple wire (night running HL, for+rev) no dim

52

32

Button Mapping

White wire map to buttons 0 and 1

33

5

Yellow wire map to buttons 0 and 1

34

6

Green wire map to button 0 for day running

35

3

Purple wire map to button 1 for night running

36

4

Motor Control

BEMF on (1)

61

1

Acceleration delay

3

12

Deceleration delay

4

12

 

 

Testing the Lights:

Button 0 should activate the day running lights (right hand headlight with both marker lights in the forward end of the car and both rear lights in the back end).

Button 1 should activate the night running lights (left hand headlight with both marker lights in the forward end of the car and both rear lights in the back end).

 

Long Cab day running lights are OK (button 0)

Long Cab night running lights are OK (button 1)

Long Cab rear lights work OK (buttons 0 and 1)

 

Short Cab day running lights are OK (button 0)

 

Short Cab night running lights are OK (button 1)

 

Short Cab rear lights work OK (buttons 0 and 1)

 

Fixing the problems:

Although the lighting operated correctly and the modified unit ran smoothly under DCC control even at low speeds, the plasticard sheet carrying the circuitry, bulged downwards under the pressure of the wiring above it, and was visible through the side windows.

The top and bottom of the unit were separated again and black painted plasticard supports were glued between the underside of the plasticard sheet and the seat backs below. The wiring was also modified, using thinner wire where possible. This cured the problem, leaving the circuitry and wires neatly hidden from view.

 

The finished Class 153

Subsequent Refinements:

The Northern Rail Class 153s and other DMUs with this latest variation on the Northern Rail livery, No longer have obstacle deflector blades painted yellow. Instead, they were initially painted black, but have since become a dark grey and rust tinted colour. The Hornby technique of bogie mounting the deflectors is not necessary if the couplers are not to be used, so I have detached the blades from the bogies, painted them satin black and remounted them via plasti-card brackets to the ends of the chassis under frame. The Class 153 photos taken in Leeds and on the Settle-Carlisle line in September 2009, also reveal pale blue painted under frame sides and roof, well weathered to now be more grey than blue, except for the extreme front and rear under frame, where the pale blue colour is very apparent. I decided not to risk re-painting the roof without an air brush to tone things down afterwards, but I have added front and rear detail to the front and back under frame in the new colour.

In a further update session, the short cab headlights have been dimmed down somewhat and the adjacent marker lights brightened a little, to make the lights more similar to those at the long cab end. The short cab headlights were also filed down to get the front faces flush with the light housings. Photos were taken to show how the headlight LEDs were fitted to each cab and the circuit diagram has been updated in line with latest values. The headlights have also been re-programmed to remove the "dimmed while stopped" facility which is not used on the real 153 units. (CV table also amended accordingly).

Revised Class 153 in Current Livery

 

An alternative approach to Class 153 lighting carried out by Marcelo from Brazil (Who models the UK Regional Railway Era):

Marcelo performed his modifications on the Regional Railways liveried version of the Hornby Class 153.

Marcelo used the same approach for his headlights as that described above, introducing new tower style LEDs that work independently to the Hornby light pipes. However, Marcelo also carefully unsoldered the original Hornby LEDs from the small lighting PCBs.  He replaced the red rear light LEDs, soldering them back in place, turned through 180 degrees, to reverse the electrical contacts. Next, he replaced the Hornby white chip LEDs with yellow equivalents and again, resoldered these in place, turned through 180 degrees compared to the original Hornby LEDs, to reverse the electrical contacts.

The reversed LED lighting PCBs now have a common positive terminal instead of Hornby's original common negative. This enables a much simplified circuit to be used with no need for transistor switching. Marcelo's new yellow chip LEDs give a more accurate light colour to the rectangular marker lights, than that provided by Hornby's white LEDs. 

Marcelo's circuit:

 

Marcelo has fitted his 153 with an ESU sound decoder. This can be programmed to define the direction of operation for all 4 function outputs. He has mapped the four functions to button 0 for daylight running or button 11 for night running. He has also fitted interior cab and passenger compartment lighting, not shown in the diagram.

I hope I have understood Marcelo's technique used to remove the chip LEDs: This involves the use of solder wick bar and flux, to remove as much solder as possible from the solder pads, then, using tweezers on the chip LED, and solder flux on the soldering iron, apply swift "jabs" at each end of the chip, until the chip LED can be withdrawn from the PCB. 

 

Marcelo's 153 with daylight running lights & cab light on.

 

Marcelo's 153 with night running lights & cab light on

 

Supplier website links:

 

York Monk Bar model shop    The Northern Rail Class 153 unit was purchased from this excellent shop in York.
Trains 4 U (Peterborough)    A good (almost local) source of Bachmann and Dapol product. They also stock TCS decoders and offer good technical advice.
Bromsgrove Models    Excellent source of DCC decoders and specialist LED devices for this type of project
DCC Supplies    DCC specialist supplier based in Worcestershire. Good prices on Tower LEDs and TCS decoders
TCS (Train Control Systems)    A U.S. company. My preferred DCC decoder family with good programming data and advice on their website.
Maplins    My usual source for resistors and transistors, with convenient local shops.

 

Photos of real class 153s were taken at Ribblehead and Leeds stations in September 2009.   The photos of the model were taken on the kitchen worktop at ISO1600 with occasional fill-in flash or at ISO200 with a tripod.    

 

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