DCC Sound and Lighting update of the
New 2012 Hornby Class 67 locomotive.
Class 67 in DB Schenker colours
This page provides a summary of the modifications applied to the new Hornby Class 67 locomotive, incorporating a DCC sound decoder and some updates to the lighting system.
Note that the smaller pictures can be enlarged by clicking on the image.
The new DB Schenker liveried variant of the 2012 Hornby Class 67, on its first test run.
|A few Initial issues with
the new Hornby Class 67 unit:
DCC control: The unit I obtained was DCC fitted, using an unspecified decoder fitted by Hornby. The loco moved every time on the minimum speed step, but became quite jittery as the speed steps were further increased up to around seven. Thereafter, movement was smooth, with a somewhat excessive maximum speed. The problem is either a mechanical issue requiring extended running-in or may simply be a poor match between the decoder back emf speed control parameters and the dynamic properties of the motor and flywheels. I will try a new ESU decoder as a first possible fix. Postscript Note: The loco runs very smoothly at all speed steps using the ESU LokSound V4 decoder.
Lighting arrangements: The New Hornby model includes directional LED lighting, with correct use of day and night headlights plus forward marker lights and rear lights. A switch on the loco underside changes the lights between day or night operation. (Right headlights during the day and left headlights at night). There are no cab lights or model driver, in spite of a fairly detailed cab interior. There is no facility to disable the rear lights when towing a train. The marker lights are too bright and pure white in colour. These will be toned down with yellow water colour paint. A new lighting control system will be fitted to enable all lighting states to be activated using the DCC controller buttons. A 6 function decoder system will be needed.
Sound System: Provision is made within the lower fuel tank to accommodate a 20x40mm speaker. Class 67 LokSound V4 sound decoders are available from Howes, South West Digital and Legomanbiffo. The ESU adapter pcb or an additional FL4 function decoder would be needed to provide all 6 function outputs for my requirement.
A Photographic look inside the new Class 67:
The chassis and upper body shell are held together with 4 screws
Lifting the main PCB reveals exposed motor leads threatening to short to one of the flywheels and a 10nF capacitor that should not be there for DCC operation.
The Day or Night running lights switch and cast metal fuel tank are fitted between the bogies.
Cast metal fuel tank removed and inverted to show the 20x40mm speaker recess.
Upper Body Shell
The LED lights are all mounted on the cab assemblies.
A lighting PCB immediately behind the front face carries the headlights, lower marker lights and rear lights LEDs.
A smaller PCB mounted on the rear bulkhead of the cab, carries the upper marker light LED.
Close up of the main lighting PCB
The electrical contacts on the main lighting PCB
Electrical contacts on the upper marker PCB
Corresponding electrical contact plates for the lighting PCBs on the chassis assembly.
Beware! the wire colour coding is different at each end.
|Circuit configuration for
the lighting PCBs:
There doesn't seem to be the usual Hornby Pic Micro on the main PCB this time. Do the lighting boards use common negative ground or common positive ground? Some careful probing with a 5 volt DC PSU and a big series resistor should reveal the answer. A 5 volt supply is too low to damage the LEDs if connected with the wrong polarity and a 10k series resistor will only allow a maximum of half a milliamp of current to flow. So by trying all combinations of connection, the circuit concept can be deduced. This will determine the circuit to be used for interfacing to the new decoder........
............Well that was a bit of a surprise!
The bad news is that Hornby are still using negative ground on their lighting PCBs. The interesting bit is the connections required to get the forward night lighting active:
Connections to activate the end lighting board LEDs
(End 1 is the roof exhaust end, end 2 is the roof ventilator end as described in the excellent 2011 Edition 2 of Traction Recognition by Colin J. Marsden)
Connections to activate the top marker light board LEDs
Extracting the cab assembly reveals the component content of the lighting PCB: One transistor, 6 x resistors (all 1K ohm) and 6 LEDs.
Transistor Q1 on the front of the PCB
I'm not going to risk damage by forcibly removing the PCB to trace the circuit, but I'm guessing the schematic looks something like this:
First issue is the relative brightness of the headlights and lower marker lights, which is virtually identical. (The headlamps should of course appear much brighter). Also the real marker lights still use old technology bulbs which appear yellow in colour.
So lets apply a fairly thick coat of yellow water colour paint to the front of the lower marker light LEDs to get the colour right and reduce intensity, plus, a less dense coat applied to the top markers.
The number two end cab with yellow water colour paint applied to the marker lights and a new (rather large) DBS driver in place.
That's more or less what I was hoping for! Bright white headlamp and much dimmer yellow hued marker lights!
The camera sensor is saturating and partially washing out the yellow content of the marker lights.
(The number 1 end headlight gets brighter when viewed exactly head-on)
|Circuit Diagram to enable
an ESU LokSound plus TCS FL4 combination to control the lights:
I'll use the spare FL4 function decoder I have in the bits box, rather than use the ESU adapter board to activate Aux3 and 4. (An FL4 + 8 pin LokSound is a much smaller physical solution than a 21 pin LokSound on its large adapter PCB.)
The ESU LokSound controls the main lighting, with the FL4 handling the rear light enable function and the cab light.
(The end 2 driver's cab [with new driver] is the only cab illuminated.)
Button 0 activates the ESU FWD function forwards or the ESU Bwd function in reverse. (Day running lights).
Button 13 activates the ESU FWD + Aux1 functions forwards or the ESU Bwd + Aux2 functions in reverse. (Night running lights).
Button 11 enables the rear lights via the FL4 brown function line. (These remain off unless button 11 is pressed).
Button 12 activates the cab light via the FL4 pink function line.
The sound options are remapped as required to permit the above arrangement.
The decoder connections
The original Hornby main PCB will be stripped bare of components and the tracks cut in such a way as to enable re-use of the 8 pin decoder connector for wheel contacts and motor connections. The multi-way lighting connectors for the lighting board interfaces will also be isolated and re-used. New circuitry will be mounted on a thin plasticard sheet, bonded to the stripped main PCB.
|Choice of sound files for
the decoder & Loudspeaker:
Searching on YouTube, good recordings of class 67 locos are not hard to find. Comparing these with clips of Howes, South West Digital and Legomanbiffo equipped LokSound decoders, suggests that the Legomanbiffo sounds closest to the real locos. These decoders are available from DC Kits & DE Videos based in Leeds and one has now been ordered.
Loudspeaker: The space is approx 22x42x8.5mm. My preferred LokSound speaker that works well in 150 & 153 has an enclosure depth of 12mm, so in this all metal environment....its too big. I've ordered a ready sealed unit from DCC Supplies that has dimensions 20x40x8mm. The drive unit is smaller than I would like, but it should fit, straight out of the box. If its not good enough, I'll construct a custom sealed box to accommodate the bigger preferred speaker.
|First run with the
I want to check the mechanical operation sooner rather than later, so while I await delivery of the new speaker, I've hooked up the new decoder to the Class 67 chassis, using just the wheel contacts and the motor connections. I've removed the 10N capacitor from the motor feed, but I left the twin ferrite core in place, having now insulated the motor wiring, before replacing the updated main PCB.
The function wires were detached from the 8 way decoder connector and carefully insulated. I kept the small circular speaker connected and temporarily taped on top, so that I can also get a feel for the sound options........
Chassis & LokSound test rig
After I reset CV2 from 1 to 3, slow speed operation was transformed! It is now both smooth and reliable. This confirms my previous suspicions about the unsuitability of the original Hornby decoder for the new Class 67 drive system!
The sound looks promising, although hopefully the larger speaker will enhance the base content a little. Tomorrow I'll sniff out the sound slot numbers, so that I can work out how to remap the sounds and functions before I test the function control. Oh yes! I've found that the small FL4 decoder I need to switch the rear light enable and cab light functions, will fit in the battery box in place of the now redundant day-night lighting switch. This should leave plenty of room for the larger LokSound decoder between the modified main PCB and the roof.
|The Legomanbiffo Class 67
LokSound V4 decoder programming as received:
The documentation is a bit thin on the ground, so a combination of listening and cv sniffing revealed the "as received" settings:
First (& final) thoughts about an overall solution for lights and sound:
Now the boring bit...... the list of LokSound cv changes required to achieve the above (derived from the LokSound manual section 12):
(The CV notation xxx/y indicates first set CV32 to y, then call up CVxxx. Change a>b indicates that initial value = a and new value = b)
Programming changes required for the FL4:
That all seems to have worked fine. So the next steps are to fit the new speaker, the FL4 and the cab light.
|Speaker and TCS FL4 decoder accommodation:
The speaker lugs were first sliced off. The unit was then inserted into the aperture in the fuel tank (facing downwards towards the open grill slots). Blu Tac was squeezed between the speaker side walls and the aperture sides to form a packing agent. A couple of small Blu Tac blobs were also compressed between the chassis underside and rear of the speaker, when the fuel tank was re-fitted. The speaker wires were extended, using heat shrink sleeving to protect the solder joints, and routed up to the top of the chassis through one of the switch wiring tunnels
To make space available for the TCS decoder, the day-night lighting switch was disconnected and unscrewed from the chassis. The TCS FL4 decoder was then wrapped in electrical tape and fitted in the switch aperture, with cabling routed up through the other tunnel to the top of the chassis.
|The LokSound Decoder is
fitted above the updated main PCB assembly:
The completed chassis assembly
The motor and wheel contact connections use the 8 pin connector. The function outputs used to drive the lighting (the other 8 pin wiring plus the purple line) are connected directly to the circuitry on the main PCB. The ground connection to the 8 pin LokSound decoder can be accessed via the GND pad indicated in the manual (in the section on "keep-alive" capacitors). This requires a steady hand and a small soldering iron bit!
Copied from the LokSound manual
The circuit shown in the diagrams above was constructed on the stripped main PCB, using hard wired discrete components, glued to a thin sheet of plasticard, bonded to the original PCB, between the end connectors. The LokSound Decoder is quite large, but must be seated low enough to clear the roof of the upper body shell. The decoder has a clear insulated plastic sleeve, so can safely (I hope) be placed on top of the other components.
Close up of the decoder
The miniature two way connector at the extreme left hand side of the photo above, connects to the new cab light fitted above the driver in the number 2 end cab.
I had a few problems with the lighting operation when the rear lights were disabled (day or night running lights). Instead of no lights at the loco rear, I got a set of day running lights. When the rear lights were enabled, all worked correctly. This was a hardware problem that I'm still a bit puzzled about, as the diodes feeding the base resistors of the rear light switching transistors should have prevented the effect. However, I increased the base resistors in series with the forward and reverse switching transistors to 100k and the problem went away. I suspect that another fix might have been not to use the LokSound ground connection but to simply connect those Hornby lighting PCB ground lines via diodes to the forward and backwards decoder lines.
I also had to adjust the series resistors to the upper marker light to reduce their intensity a little and I had to physically move the cab light further away from the top marker lightpipe, to reduce light pick-up, which was visible through the upper marker lens when the running lights were off.
The circuit changes are all now included in the circuit diagram higher up the page.
|Fitting the "add-ons":
The front coupler, air dam, pipes and orange devices were fitted to the front end, in my case, the number two end, complete with driver.
Then, as a tension-lock coupler is required to attach to the train, the original air dam needs some attention to clear the coupler. The buckeye was omitted in case it interferes with the tension lock mechanism.
One train destined to be hauled by 67018 is my set of 5 re-wheeled Lima Mark 3s in the old blue-grey BR livery. The tension lock couplers on these coaches are not a good match for the more modern Class 67 types. In particular, the hook bar is longer on the Mark 3. This confirmed the decision not to fit the dummy buckeye coupler to the rear of the Class 67.
|Refining the CVs:
The engine sounds benefit from a boost in volume as the revs wind up during initial acceleration. I can incorporate this into the computer schedules. I have programmed button 18 so that the LokSound fader is on when the button is off and off when the button is on. This results in a volume booster via button 18! I have found that with CV133 (fader volume ratio) set to 75 and CV63 (master volume control) set to 80, I get the effect I'm looking for. If the volume booster is switched off at the start of the air release at a stop, the reduction in volume to idle level is not too obvious.
The two tone horn was previously reduced in volume but I overdid this on the lower tone, which needs a bit of a lift. (Reset from 70 to 80 and the cv change table above has been updated.) The flange squeal effect is now activated when the volume level is boosted. This has therefore also received a volume adjustment, down to 90.
There is a slight sign of uneven running at around half of max. speed. I will run the LokSound self-calibration routine to optimise the motor control CV settings in an attempt to achieve smooth running at all speeds. (See the table in the next section, to see what has changed.)
Further light level adjustment.....
The top marker lights were still a little too bright, so I've changed their series resistors to 4k7. (Circuit diagram above was also updated).
|Optimising the motor CV
The procedure is to place the loco at the start of a long straight track (circa 3m). Having set the direction of travel ahead, CV 54 is set to zero, then control key F1 is pressed, to send the loco forward at maximum speed for a second or so, before bringing it to a standstill. During this brief high speed run, the decoder analyzes the motor characteristics and resets the key control CVs (51 to 55) to optimum values.
No dramatic changes and no obvious change to performance. But one parameter looks very wrong to me! CV55 is related to the mechanical inertia in the drive system with a default value of 100. This loco has a 5 pole motor and two massive fly wheels. I think 100 is probably a more appropriate figure...... and sure enough, the slight speed wobble at half speed goes away when CV 55 is increased to 100.
|The complete Mark 3 Train:
Five Lima Mark 3s from well over 20 years ago. I had already changed the wheels for code 75 rail compatibility.
And that completes another project..........Better get back to that loft layout so I can give the train a meaningful run!
A new larger speaker:
The sound level and frequency response of the initial DCC Supplies 20x40x8mm speaker (with a 30x15mm drive unit) doesn't compare well with other locomotive speakers in the collection. However, it is just possible to squeeze an ESU 50334 20x40mm drive unit enclosure into the fuel tank casting...... except that the enclosure is a little too deep from front to back. Nothing that can't be resolved with a junior hack-saw!
The rear of the enclosure will be pressed hard into the chassis underside, but to ensure the enclosure is air tight, a 0.25mm thick plasti-card rear plate was first glued to and then sealed to the enclosure sides. The speaker drive unit was pushed approx half a mm below the rim of the enclosure in an attempt to prevent extreme cone movements from hitting the central grill support inside the metal fuel tank casting (I would have removed the central support if the casting had been made of plastic.)
(The drive unit has been temporarily placed unsealed and flush with the enclosure rim in the above photo.)
The new enclosure is a very tight fit into the fuel tank casting and is very slightly deeper than the available space. This results in firm down pressure on the enclosure, holding it very firmly against the chassis underside and hence countering the danger of the thin back plate flexing.
I was relieved to find that not only was there no hint of the speaker cone hitting the grill support, but the sound level and bass response were a huge improvement on the smaller original speaker!
To see a brief Youtube clip showing the class 67 in action on the test track, with its new speaker: Click here
|Activating manual notch
ESU provide a notch-up and notch-down facility and Bif designs his sound projects to be compatible with the system. It enables faster light engine cruising with the engine at idle or, when trying to move a heavy train, the engine power can be wound-up before departure.
To set Notch-up on button 19: Set CV32 to 3 then set CVN=397 to 2.
To set Notch-down on button 20: Set CV32 to 3 then set CVN=413 to 4.
|Supplier website links:
The photos of the model Class 67 were taken using a Canon Ixus 220HS on the kitchen worktop with on-board flash.