Colas livery Bachmann Class 70 from Olivia's (livery by R3Sprays).



Bachmann's own proposed Colas Class 70 looks as far away as ever, so when Olivia's kindly offered me an alternative to their now withdrawn new logo DRS 37, The Colas 70 was an obvious choice. R3Sprays have worked their usual magic and done an excellent re-spray job! So now I have the opportunity to modify the lights on a Colas 70, in line with recent RMweb forum contributions from "Big Jim" who regularly drives these machines and has described the lighting operation in some detail.

Bachmann's original day headlights are dimmer than the marker lights. This needs fixing, night headlights are added and automatic control of the marker light configuration is incorporated. (When operating in the yard, all three markers are active, with no headlights. When operating on the main line, day or night headlights are activated and the marker immediately adjacent to the active headlight, automatically switches off.) 

Previous Class 70 lighting update web pages outline the details of similar modifications to the Freightliner Class 70. Although I plan to use a LokPilot FX V4 function decoder this time, in support of the same Bif LokSound V4. That way, there is no need for the discrete PNP transistors and MOSFET buffers.  I'll omit the detonator flash LED and double strobe warning lights this time as neither get a lot of exercise on the previous Freightliner unit.


Illustrating the Class 70 lighting options with photos obtained from the RMweb forum, with many thanks to "Big Jim" for permission to use them!

                  In the yard with all three forward markers illuminated, but no headlight.

Showing the dual function lower marker lights in rear light mode                             

Day running lights with right hand headlight on and the right hand marker light off.

Night running lights with left hand headlight on and the left hand marker light off.



The Proposed Circuit diagram:

Keeping it simple with a LokPilot FX V4 function decoder.

Activating each headlight, disables the adjacent marker light via the diode connecting the two. Reverse bias protection diodes are also required.

All lighting at End 1 (driver's end) is via the LokPilot FX function decoder. Lighting at the other end is via the LokSound decoder.



Mods to the lighting PCBs adapted from the previous project:

The original lighting circuit is as follows:


A few changes are needed:

The additional series resistors are at the main Board end of the interconnecting cables.   The links and track cuts shown above need to be implemented. I'll also replace the original stiff cables between the lighting boards and the main board with more flexible types.

Lighting PCBs with the key tracks indicated in green:

NB: The lower picture is a photo shopped mirror image to make it easier to see how the vias link the top & bottom tracks!

Black rectangles on the upper photo show where original resistors have been removed; red line = track cut; blue line = new link.

Yellow triangle shows connection points for the now remotely mounted day headlight LED leads. Yellow arrow = extra wire link back to main board.


Proposed new FO mapping arrangements: 


Select Action Direction & Key Condition, F Key,  FO(s) Mapping line
End 1 Mkr/rears Set End 1 directional markers and rear lights (LokPilot FX) Fwd F20 Fwd, F(20), LP White  (FO H/L) (F0 & F26 off) LP 1
Rev F20 Rev, F(20), LP Yellow (FO R/L) (F0 & F26 off) LP 2


End 2 Mkr/rears Set End 2 directional markers and rear lights (LokSound) Fwd F21  Fwd, F(21), LS white (FO H/L) (F0 & F26 off) LS27
Rev F21 Rev, F(21), LS Yellow (FO R/L) (F0 & F26 off) LS35


Select Action Direction & Key Condition, F Key,  FO(s) Mapping line
Day headlights Set End 1 day H/L fwd only if F20 active (LokPilot FX) Fwd F22 Fwd, F(22), LP (FO 1) (F20-on)  (F23 off) LP3
Set End 2 day H/L rev only if F21 active (LokSound) Rev F22 Rev, F(22), LS  (FO 1) (F21-on)  (F23 off) LS28


Night Headlights.... Set End 1 night H/L fwd only if F20 active (LokPilot FX) Fwd F23  Fwd,  F(23), LP  (FO 2)   (F20-on)  (F22 off) LP4
Set End 2 night H/L rev only if F21 active (LokSound) Rev F23 Rev,   F(23), LS  (FO 2)   (F21-on)  (F22 off) LS29


Select Action Direction & Key Condition, F Key,  FO(s) Mapping line
Parking Rears Set rear lights at both ends (LokSound & LokPilot FX) Both F0

(Stationary only)

F(0), LP Yellow (FO R/L)   (F20 & F21 off)

F(0), LS white  (FO H/L)   (F20 & F21 off)

LP 5

LS 5


Super Shunter mode Flash rears and markers alternately (LokSound & LokPilot FX) Both F26 F(26), LP config 2 FOs H/L & R/L, flash mode, R/L phase shift, (F0 & F20 & F21 off)

F(26), LS config 2 FOs H/L & R/L, flash mode, R/L phase shift, (F0 & F20 & F21 off)

Flash speed via CV112 =20  (LP & LS)






Select Action Direction & Key Condition, F Key,  FO(s) Mapping line
End 1 Cablight.... Set cab light  (LokPilot FX) Both F12 (Stationary only) F(12), LP orange (FO3) LP 6



Programming LokPilot CVs for new lighting arrangements:

Mapping line Key  Alpha values CV32 Actual CV values
1 F20 > CVA=36,CVF=16,CVH=2,CVK=1 2 257=36, 262=16, 264=2, 266=1
2 F20 < CVA=40,CVF=16,CVH=2,CVK=2 2 273=40, 278=16, 280=2, 282=2
3 F22 > CVA=4,CVF=16,CVG=9, CVK=4 2 289=4, 294=16, 295=9, 298=4
4 F23 > CVA=4, CVF=16,CVG=6, CVK=8 2 305=4, 310=16, 311=6, 314=8
5 F0 <> CVA=18,CVF=160,CVK=2 2 321=18, 326=160, 330=2
6 F12 <> CVA=2,CVD=16,CVK=16 2 337=2, 340=16, 346=16
7 F26 <> CVA=32,CVF=160,CVH=1,CVL=48 2 353=32, 358=160, 360=1, 363=48
0 355=12, 363=12, 367=1, 112=20



Programming LokSound CVs for new lighting arrangements:

Mapping line Key  Alpha values CV32 Actual CV values
27 F21 > CVA=36,CVF=64,CVH=2,CVK=1 3 417=36, 422=64, 424=2, 426=1
35 F21 < CVA=40,CVF=64,CVH=2,CVK=2 4 289=40, 294=64, 296=2, 298=2
28 F22 < CVA=8,CVF=64,CVG=9,CVK=4, 3 433=8, 438=64, 439=9, 442=4
29 F23 < CVA=8,CVF=64,CVG=2,CVK=8 3 449=8, 454=64, 455=6, 458=8
5 F0 <> CVA=18,CVF=160,CVK=1 2 321=18, 326=160, 330=1
6 - clear CVA & CVK to zero 2 clear out  337onwards
32 F26 <> CVA=32,CVF=160,CVH=1,CVL=48 3 497=32, 502=160, 504=1, 507=48
0 355=12, 363=12,367=1,112=20

All working as planned!



Function list     (Lighting options highlighted)

F0 Parking rears
F1 Sound On/Off and engine start/stop.
F2 Playable High Note Horn.
F3 Playable Low Note Horn.
F4 Buffer Clash/Buffering up when moving slowly.
F5 Air Release (Air Dump).
F6 Drivers door slamming.  
F7 Compressor Startup.  
F8 Dynamic Braking Fan Enable. 
F9 Flange/Wheel Squeal Enable.
F10 Dispatcher's whistle.
F12 Cab light
F14 Notch-up.
F15 Notch-down.
F17 General Electric Skipfire Idle Enable.
F18 Triple Detonators.
F19 Set zero momentum (for test purposes only).
F20 End 1 markers & rears
F21 End 2 markers & rears
F22 Day headlights
F23 Night headlights
F26 Alternate rears & markers: Super shunter mode.

The completed function list mirrors the freightliner Class 70 except for the lighting,

which is now simpler to set up and has slightly different functionality.


The physical circuit implementation:

The function decoder, end 1 series resistors and diodes will sit on a thin plasticard substrate in Bachmann's speaker bay at the driver's end of the chassis block.  The end 2 resistors and diodes will sit on another small plasticard sheet glued to the top of main PCB (in place of the original SMD parts towards the end 2 end of the board).

There will be unused cable(s) in the connectors to the upper body shell. These will be used (together with a shared common positive feed) to drive the night headlights in the upper body shell.

Wheel contacts, motor connections and speaker tabs will remain active on the main board, while common positive and function outputs will be linked on to the new plastic substrates. New connections and track cuts will be made as necessary to the two 4-way connectors on the main board for interfacing to the upper body shell. 

Stay-alive 25V capacitors will be fitted in any remaining space in Bachman's speaker bay.     Only room for 2000uF, but every little helps!



The conspicuous lamp brackets that should be fitted to the inside edge of the right lighting boxes are missing. So a bit of plasti-card construction will be necessary to remedy that omission.

The set of 4 circular observation windows in the orange painted zone of the body side have been over-painted with orange. A drop of gloss black paint is required here.

The triangular cab side panel extensions immediately behind the obstacle deflector should be matt black rather than the orange or yellow Colas colours. Another minor paint job required here!



The completed Colas Class 70


To see a brief video of the Colas 70 please click here


Supplier website links:


Olivia's    The Colas Class 70 unit 70801 was sourced from this supplier.
R3Sprays    The re-spray into Colas colours was carried out here.
DC Kits - D&E Videos    The source for Legomanbiffo sound equipped LokSound V4 decoders.
Coastal DCC    Source for the LokPilot FX V4 function decoder.
Digitrains    Source for the new pre-wired Nanolight chip LEDs.
Maplin    Convenient local source for resistors and transistors, although the prices reflect that convenience.
Amazon    Unexpected, but effective source for low price electronic components in small quantities at reasonable prices.


Photos of the real class 70s were taken by "Big Jim" & copied with his permission (Thanks Jim!) from the RMweb forum site.   The photos of the model were taken via EOS 760D in the loft.


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