Bachmann's new livery Freightliner Class 66........ A Bif LokSound V4 and additional EM1 speaker are planned to compare operation with the original Paul Chetter Protodrive system on a Zimo MX644D decoder, initially fitted to this locomotive.


Another member of the class, with the new livery.                                   With thanks to Kevin Bates for the photo.



The new Freightliner liveried 66 was the fourth 66 to receive the Zimo conversion treatment, including "Yard Mode" and "Super Shunter" lighting options. I'm now going to try an alternative LokSound V4 scheme

Inputs from loco drivers on the RMweb site indicate that when picking up or dropping trains in the yard, headlights are switched off to avoid dazzling the yard staff. This results in "Yard Mode" lighting, with forward markers and rear lights active, but no headlights.

Occasionally, with the demise of dedicated small shunting locos such as the previously ubiquitous Class 8, large freight diesels are used to assemble trains within the yard. When undertaking this task, the preferred lighting arrangement is to display red rear lights and white marker lights simultaneously at both ends of the locomotive. However, if modern dual function LED combined rear / marker lights are in place on the locomotive, this arrangement is not possible. However, a little imagination results in these lights emitting alternate red and white flashes, providing an effective equivalent set of warning lights. Hence "Super Shunter" Mode.

The New LokSound V4 scheme:  Providing identical functionality. The downside is that an extra function decoder is needed, however, thanks to the comprehensive LokSound function mapping arrangements, the rest of the hardware is somewhat simplified.  I like the drivelock feature now incorporated in Bif's diesel sound projects and this will give me the opportunity to make a direct comparison with Paul's Zimo Class 66 arrangements, which in their default mode use notch transition speeds a little on the slow side to my preferences. I can get around this by using full manual notching, but this requires very active concentration when driving and a lot more work on the PC control programme when setting this up for video work.

I'm also going to try to incorporate an EM1, the smaller version of the earth mover speakers, immediately below the body shell roof. This device has a limited power handling capability, so I'll connect it in series with the 4 ohm 40x20mm ESU speaker already installed in the fuel tank. Finally, the 2000uF stay alive capacitor will be increased to a 6800uF AVX super-cap with a limiter to keep the charging voltage within specification....... I'll leave the Zimo data in place at the bottom of this web page and document the EM1 plus LokSound V4 and LokPilot FX solution immediately below:


The planned LokSound/LokPilot FX V4 Circuit:


Although an additional function decoder is needed, the comprehensive ESU function control system permits a slightly simpler hardware circuit solution to drive the

various lighting options. Only complicated by the use of the buffer amps, to make use of Bif's detonator synchronised LED drive signal on Aux3 and to keep the

 "stationary only" cab light switching exactly synchronised with the loco's movements. A super-cap safety circuit ensures that the 15V maximum charge voltage of

the AVX capacitor is not exceeded due to higher controller DCC output levels.


Function distribution between the two decoders:

LokSound V4

Fwd       fwd switch    and Fwd top Mkr

Rev        Rev switch    and Rev top Mkr

Aux1      day H/L

Aux2      Night H/L

Aux3 Via MOSFET buffer   detonator flash LED (if fitted)

Aux4 Via MOSFET buffer Driver's cab light    (on when stationary only)


LokPilot FX V4

Fwd       rears end 2                       conf.1 continuous mode         conf.2 flashing light mode, phase 0

Rev        rears end 1                       conf.1 continuous mode         conf.2 flashing light mode, phase 0

Aux1      lower Mkrs                        conf.1 continuous mode         conf.2 flashing light mode, phase 1



Function Mapping:

Function Key Function Action
0 Parking lights on (rears at both ends)
1 Sound on
2 Playable High Horn
3 Playable Low Horn
4 Buffer clash moving, coupling hook stationary
5 Playable brake application moving, air dump stationary
6 Drivers door slam
7 Compressor speed up
8 Drivelock
9 Flange squeal
11 Cab light
12 Cooler group fan (speed dependent)
13 Sanders
15 Spirax valves
18 Detonators (with synchronised LED flash)
19 Sound fade to half volume
20 End 1 yard mode lights (markers / rears)
21 End 2 yard mode lights (markers / rears)
22 Day headlights
23 Night Headlights
24 Super-Shunter mode lighting


More detail on the LokSound Lighting Function Data:

F11 (stationary only): Aux 4 on

F20 Forward:  HL on

F21 Reverse:  RL on

F22 + F20 Forward :  Aux 1 on

F22 + F21 Reverse :  Aux 1 on

F23 + F20 Forward :  Aux 2 on

F23 + F21 Reverse :  Aux 2 on

F24 : HL on + RL  on


...& the LokPilot Lighting Function Data:

F0   HL (conf 1) on + RL (conf 1) on

F20 Forward: Aux 1 (conf 1) on

F20 Reverse: RL (conf 1) on

F21 Forward: HL (conf 1) on

F21 Reverse: Aux 1 (conf 1) on

F24: HL (conf 2) on + RL (conf 2) on + Aux 1 (conf 2) on

(conf 1 = continuous;  conf 2 = flashing light, with HL & RL at phase 0 and Aux 1 at phase 1) flash duration reset to one second.


The above arrangement was programmed via an ESU LokProgrammer, avoiding the need to work through the individual CV values.

All working fine!


Physically accommodating the EM1 speaker and the two new decoders:

The EM1 is only 9mm deep, which enables it to fit between the roof and the chassis block in the current location of the main PCB. The main PCB is replaced with an ESU 21 pin adapter to connect the LokSound decoder. There is plenty of space immediately behind the driver's cab bulkhead to accommodate a wired version of the LokPilot FX function decoder and a few additional hard wired components. (A bit more work than originally intended, but worth it to see if the EM1 speaker provides enough additional bass content to justify equivalent work elsewhere.)

Looking good so far..... I've removed the mounting columns for the PCB at the roof fan end of the chassis block, and the speaker can be mounted via plasticard supports and an insulator, down on to the chassis block, facing upwards. The 21 pin decoder fits on its ESU adapter board between the driver's end PCB mounting columns, beside the new speaker and the LokPilot FX function decoder will fit directly behind the driver's cab bulkhead. Leaving the original plasticard substrates for the extra series resistors etc in their original locations

Showing the new parts placed in their new locations before I wire it all up and bond it all down.  (The new supercap will replace the old electrolytics).

I will replace the original stiff body shell wiring with a subset of more flexible wires and use a single new flying lead connector between top and bottom assemblies.


Lots of wire to connect up.....but fortunately, it all seems to work OK!



The lighting system operates correctly and the locomotive behaves well under Bif LokSound control. The Drivelock system works well, providing a simple and effective means to de-couple the engine sounds from the line speed whenever appropriate.

The EM1 speaker is a little disappointing. Its bass response does not seem to be significantly better than the original fuel tank mounted ESU 20x40 device.  Its a lot smaller than the big EM2, so I guess this should not be a big surprise, but it means that I'm unlikely to use an EM1 in subsequent DCC sound conversions...... We live and we learn. 

The Bif LokSound driving characteristics seem to offer a better fit to my requirements, now that drivelock has been incorporated.  Control may not be as flexible or as comprehensive as on the Zimo decoders, but the wider distribution of the Bif engine sound notch transition points, across around 85% of the speed range, I find works somewhat better for me than the more closely spaced transitions seen in the default Paul Chetter Zimo solutions, which typically arrive at the top notch at a very much smaller proportion of the max speed and often result in me fighting the automated system in an attempt to reduce the notch levels at higher cruising speeds.


Next a driving comparison between an earlier Zimo equipped 66 and the newly updated LokSound locomotive.........

A little problem here! All my other Zimo 66s have been configured for full manual notch control. This gives total engine sound control, independent of loco speed and works well as long as the driver is prepared to put the extra work in! However, more recently I've been using my Zimo locos in automatic mode, but with the ability to ramp up the engine notch setting to around 3/4 max, independent of speed to enable heavy load starting. This is the mode I need to change my comparison Zimo 66 into in order to compare driving feel with the new LokSound plus drivelock arrangement in the Freightliner unit:

I'm going to attempt to convert my full manual notching Zimo equipped Colas liveried 66, to semi-automatic operation, the following CV changes are required (I hope):

CV number Original FMNC 66 value Semi auto value
339 5 7
340 49 3
345 0 0
347 9 5
348 2 7
387 0 180
389 0 10
390 128 128
391 235 40

Yup!  That works fine.....   At slow speed, the driving characteristics are very similar..... The Bif loco notch automatically drops back from notch 1 to idle when travelling at very slow speed, simulating light engine operation. The Zimo loco has a light engine key, which reduces momentum and the initial notch-up can be shut back to idle using the coasting key. So different technique but similar very acceptable performance.

A simulated heavy load start works well on the Bif unit using drivelock to ramp up the notches just before the loco moves.  The power-up key provides an equivalent technique on the Zimo locomotive. So nothing to choose so far.

The Zimo loco is equipped with a brake key (which can be disabled if auto-stop is preferred) Bif hasn't yet implemented the equivalent facility that I believe is now possible on LokSound....... but this may be because the facility cannot be disabled by the user on LokSound if not liked? (purely my speculation) which would mean it has to work very well indeed before implementation.   The Zimo arrangement works well and operation can be adjusted by the user if required.

(However, Bif has developed a synchronised detonator flash LED drive waveform which also works extremely well...... so Zimo don't have a monopoly on unique features.)

The next area of comparison is at higher speed, so I will have to move the locos up to the loft layout, where a continuous track circuit can allow higher speed comparison without worrying about running out of track! But first, a rolling road test to establish the notch changing speed thresholds.......... This reveals a significant difference in behaviour (when driven by a DCC controller in 28 step mode).

Bif LokSound: Apart from the transient effect of a brief burst at notch 1 when lifting the speed above zero, followed by a more permanent notch up from idle to notch 1, the Bif LokSound exhibits repeatable thresholds with minimal hysteresis between slow up and down movements through the speed levels. 28 step thresholds are at 1 for the short initial notch 1 burst, then at 6 for a permanent notch 1. Notch 2 comes at 12; notch 3 comes at 18 and top notch 4 comes at 23. On the way down, the thresholds are similar except that idle is reached at speed step 7.

Zimo: Going slowly up through the 28 speed steps, the threshold speeds are much more difficult to identify....... This is due to the Zimo system of ramping up to the notch above when it first detects a small increase in the speed setting and dropping down to the next lower notch level when it first detects a reduction in speed. This makes it tricky to work out the notch level thresholds. Just searched through the manual for any clues on user CVs that might disable this facility... but the only CVs I identified as possibles slightly altered the notch change behaviour but not sufficiently to disable the issue. So reverting to the standard CV settings..... Winding up slowly through the speed steps, results in reaching the highest notch at speed step 14. However reducing speed to 12 in two slow steps takes the sound notch right down to idle....... where it stays as the speed is slowly further reduced to zero......  so there must be other mechanisms involved.

I'll have to run the locos on the loft layout loops to see how they operate in real driving situations. 

In fact a few test runs on the continuous tracks in the loft layout, indicate that the two locos for all practical purposes both work very well. They are both very smooth performers with very convincing sounds produced. Thanks to Drive lock, the LokSound V4 can now perform heavy train starts realistically and can revert to idle whenever required. These capabilities have previously only been available on appropriately programmed Zimo decoders. Zimo still has the advantage of a user adjustable braking key facility and user adjustable key switchable light engine mode. While Bif's synchronised detonator LED drive on LokSound V4, is unique to the best of my knowledge .

Note: I used my PC to drive the Lenz system in the loft so that I could bring up the two cab windows, together on the screen. This produces an output that is at least equivalent to a 128 step controller, which may change the behaviour of the locos compared to that seen previously, using the Lenz controller in 28 step mode.


Comparison Conclusions:

Driving / sound interaction

Zimo is still the decoder of choice for those who enjoy delving into its sound related driving capabilities and making their own configuration and fine tuning adjustments, as the design philosophy clearly supports this. About the only aspect of loco behaviour that cannot be adjusted is the transition speed step for each engine notch change, which is determined within the sound project for normal running. Paul's projects typically set these to enable the full range of notch changes to be achieved at or below mid speed. This means that cruising at any speed above half, runs at the max notch setting without intervention. However there are several ways available to the operator to reduce the cruising notch to lower settings if required. For those requiring total control (and willing to apply the concentration required to get it right) even full manual notching control is possible in a very responsive way, enabling any notch to be selected at any speed.

Bif's Drivelock equipped LokSound V4 solutions do not have much in the way of driving related sound, user customisation opportunities...... however for most enthusiasts, the offering straight out of the box, works very well indeed without the need for further adjustment.

Lighting Function Control

For lighting control, I find the ESU LokSound V4 solution extremely good and much more flexible that Zimo's "Swiss Mapping" technique. The big advantage of Zimo is the higher number of hardware function outputs, while a complicated LokSound V4 lighting installation may well require the use of an additional function decoder.

Bottom Line:

So..... as I guess you would expect:   Both Bif ESU LokSound V4 and Paul Chetter protodrive or active drive Zimo solutions provide impressive Class 66 Diesel sound system results, each with its own strengths and weaknesses.  Straight out of the box, Bifs V4s are a really good solution.  Zimo is not quite so intuitive, but if you are prepared to put in the effort, it also provides really good results and has plenty of flexibility to explore.







The page continues with a description of the original Zimo equipped unit.......


A few quality problems encountered upon receipt of the loco:

The new 66 had a number of issues straight out of the box:

1) When I separated the chassis assembly and the upper body shell, the black wheel contact wire on the rear bogie was detached from the bogie and there was a piece of heat shrink sleeving over the black wheel contact wire of the front bogie, just where it emerged from the chassis block. (the sleeving covered a short section of exposed copper wire.)

2) When I dismantled the locomotive, ready to install the speaker (in the bottom of the fuel tank) it became obvious that the drive shaft into the front bogie was very stiff and difficult to turn.

Further investigation revealed the reasons for most of the above issues:

a) The holes in the chassis block through which the wheel contact wires pass had severe sharp edged burrs around their inner edges. I guess these had gone through the insulation of the sleeved wire and may have snagged the broken wire. Easily fixed once identified, with a few drills and needle files. (The damaged wires will be replaced with new ones.)

b) The outer frame around the front bogie was not correctly clipped in place and was rubbing on the outer wheel pair's gear wheel. Additionally the worm gear bearings appeared dry. The bogie frame was removed, the worm gear bearings lubricated and during re-assembly, care was taken to properly clip the frame in place.  The shaft now turns without undue resistance.

The bogie mountings to the chassis block also seem rather loose and may require attention to improve the fit, when the locomotive chassis assembly is rebuilt! ......... (Appears OK after additional tightening during re-assembly.)



The Original Zimo Hardware update:

Revised Circuit diagram for later build Class 66 locomotives with dual marker/rear lights:

Resistors coloured brown are the only original surface mount parts


Main PCB Mods  (X = remove component)


Additional circuitry required: PNP devices are BC559C, MOSFETs are 2N7002 and diodes are 1N4148. LEDs are pure white 0603 chip types.


The small End 1 roof mounted lighting board was also modified to provide independent positive feeds to cab and marker light LEDs (to enable the cab light to be used regardless of the set direction).


Implementing the Zimo Hardware Updates:


Lots to do!   First the speaker installation in the bottom of the fuel tank.

An ESU 50334 20x40mm speaker is glued and sealed into a rectangular aperture cut in the bottom of the fuel tank. The top of the fuel tank is then filled with a rigid plasticard sheet which includes a fabricated curved indent to accommodate the bottom of the motor (which protrudes a little, into the the top of the tank). Care is taken to make the modified fuel tank completely air tight for optimum speaker performance.


Lighting Updates:

0603 pure white LEDs are fitted to the unused pads on the Bachmann lighting boards to provide the night headlights, which are wired using the spare pad also provided on the PCB.  Pure white pre-wired chip LEDs are fitted to the lighting frame moulding to form the lower marker lights. (Details of this process can be found on the Class 66 page in the lower section of the website.)


Next, a lot of work is required to modify the main PCB.

Most of the original surface mount components are removed. Several tracks receive cuts and a number of link wires are soldered into place.  Additional wire connections are made to the 21 pin connector base to facilitate contact with the decoder connections that are not supported by the original Bachmann assembly. Then the two N-Channel MOSFETs are glued to the PCB and their supporting components are fitted. The area below the decoder is kept clear of components and covered with an insulator to prevent any accidental shorts.


Minor change to the driver's end roof lighting board:

Minor changes are also made to the driver's end roof mounted lighting PCB, using the spare wire to provide independent positive feeds to the cab light and upper marker light LEDs.


The remaining circuitry is accommodated on plasticard substrates, glued to the top of the chassis block.

The components are glued to the plastic substrates using "Glu 'n Glaze". The bonds are good enough to hold everything in place but can be broken if changes are needed (which is why I've not used super glue)



There is lots of scope for mistakes, so uncharacteristically, I decided to run a formal test process to make sure the hardware was operating correctly, before I fitted the DCC decoder.

Fortunately, for once, it all worked first time, so I could be confident that any subsequent issues would probably be due to decoder programming slip-ups.



CV Programming Changes:


Summarising the lighting requirement:

Swiss Group Function Key Lighting mode Description Forward 1 Forward 2 Reverse 1 Reverse 2
1 F26 Parking Rears FO7 FO8 FO7 FO8
3 F20 End 1 Mkrs & rears (also = Yard Mode) FO(H/L) FO3 FO7  
4 F21 End 2 Mkrs & rears (also = Yard Mode)   FO8 FO(R/L) FO3
5 F22 Day Headlights FO1   FO1  
6 F23 Night Headlights FO2   FO2  
7 F25 Super Shunter FO(H/L) FO(R/L) FO(H/L) FO(R/L)
8 F25 FO4   FO4  
9 F25 FO7 FO8 FO7 FO8
2 F0 Cab Light FO5   FO5  
9 F17 Detonator Flash    (F16 M-key)  [Not fitted] FO6      


General CV Settings:

CV3 increase to 100

CV4 increase to 120

Set CVs 33 & 34 to zero

Set FO7 & FO8 to logic FO (not Suzi) CV124=128

Set max vol to 65  CV395 =65

Set motor control to 40kHz   CV112=32

Increase light engine momentum  CV390=120

Set power ramp-up ceiling to notch 3 CV340=3

Lighting CV Elements:

CV131=60 to automatically switch off the cab light (FO5) when the loco is on the move.

CV118 defines FO to flash... for FO4, value=32

CV117 defines flashing waveform...  for 1/2 sec on and 1/2 sec off, value = 55


Swiss Mapping CVs:

Description CV


Group 1      F-Key 430 26
M-Key 431 0
1st fwd FO 432 7
2nd fwd FO 433 8
1st Rev FO 434 7
2nd Rev FO 435 8
Group 2     F-Key 436 29
M-Key 437 0
1st fwd FO 438 5
2nd fwd FO 439 0
1st Rev FO 440 5
2nd Rev FO 441 0
Group 3      F-Key 442 20
M-Key 443 0
1st fwd FO 444 14
2nd fwd FO 445 3
1st Rev FO 446 7
2nd Rev FO 447 0
Group 4      F-Key 448 21
M-Key 449 0
1st fwd FO 450 0
2nd fwd FO 451 8
1st Rev FO 452 15
2nd Rev FO 453 3
Group 5      F-Key 454 22
M-Key 455 0
1st fwd FO 456 1
2nd fwd FO 457 0
1st Rev FO 458 1
2nd Rev FO 459 0
Group 6      F-Key 460 23
M-Key 461 0
1st fwd FO 462 2
2nd fwd FO 463 0
1st Rev FO 464 2
2nd Rev FO 465 0
Group 7      F-Key 466 25
M-Key 467 0
1st fwd FO 468 14
2nd fwd FO 469 15
1st Rev FO 470 14
2nd Rev FO 471 15
Group 8      F-Key 472 25
M-Key 473 0
1st fwd FO 474 4
2nd fwd FO 475 0
1st Rev FO 476 4
2nd Rev FO 477 0
Group 9      F-Key 478 25
M-Key 479 0
1st fwd FO 480 7
2nd fwd FO 481 8
1st Rev FO 482 7
2nd Rev FO 483 8


Revised Function Mapping:

Key Action
0 Cab light (forward & stationary only)
F1 Engine start/stop
F2 Brake
F3 Horn hi tone (playable)
F4 Horn two tone hi-lo (fixed)
F5 Light engine
F6 Force engine to idle
F7 Engine ramp to notch 3
F8 -
F9 Flange squeal
F10 Brake air release
F11 Brake squeal
F12 Spirax valves
F13 Horn lo tone (fixed)
F14 Prime (on) / start alarm (off)
F15 Fan door snap open--- fan (on) fan door snaps shut (off)
F16 Horn two tone lo-hi (fixed)
F17 Dispatcher whistle
F18 Cab door slam
F19 Fader
Select which end(s) require lights (one end or both)
F20 End 1 yard mode lights
F21 End 2 yard mode lights
Select Day OR Night Headlights
F22 Day headlights
F23 Night headlights
OR, select specialised lighting
 F25 Super shunter mode lights
F26 Parking rears
F27 Volume down
F28 Volume up


Lighting mode Descriptions and key combinations:

Lighting mode :

 Key combination

Cab light (driver's end only)           0 (stationary only)
Parking rears both ends 26
Day running Lights (light engine)      20,21,22
Night Running Lights (light engine)    20,21,23
Train Haul day (coupled at end 2)     20,22
Train Haul night (coupled at end 2)    20,23
Yard mode light engine 20,21
Yard mode train haul 20
Super shunter 25


All working fine



Another of Kevin's new livery photos...


Cosmetic Adjustments:

1) Fitting the front dam and hoses.

2) Modifying and fitting the rear dam to accommodate the tension lock coupler.

3) Possible weathering of the ventilation grills exhaust etc.


To see a Youtube video of the loco, please click here


The project continues...................

Supplier website links:  


Digitrains A good source of all things DCC including pre-wired chip LEDs from DCCC and Zimo decoders.
Rapid Electronics A good low cost, high speed supplier of electronics components etc
Maplin A convenient local source for electronic components such as resistors and transistors (but at a cost)




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