The Snapper's DCC Workshop - Heljan 37/4

Discussion in 'Techniques' started by TheSnapper, 19 August 2017.

  1. TheSnapper

    TheSnapper Western Thunderer

    I’ve been thinking about starting a thread for some time and fellow Thunderers that I have consulted about the idea have encouraged me to give it a go..

    I have probably done more than 50 DCC decoder installations, both for myself and for “clients”, friends, colleagues etc. Most have been in 7mm scale, although I have done some 4mm & Gauge 1 too. The majority have been sound installations.

    I get all sorts in the “Works” – loco's that jerk along on DC, loco’s that don’t run at all, loco's with so much lead added that there’s precious little room for a decoder, never mind a speaker or stay alive unit.

    I just thought that there might be some interest in seeing how some of these installations progress and the problems I encounter, and the way I get around them, or not, as the case may be. Yes, I have refused to do installs before, for one reason or another. DCC is not a cure-all – if it don’t run on DC, there’s no chance that DCC will make it any better!

    Caveats: I can’t promise that my photos will be studio quality (like Mickoo’s or Dikitriki’s for instance), as they will often be grab-shots, done in a hurry. Also, the content may a sporadic, as I do other things too, such as go to work!

    And another thing: By no means do I intend this to be “The Definitive Guide to DCC Installations”, or the “Ultimate DCC Knowledge Base”. There are several others on this Forum who are far more qualified than I am to supply learned answers to technical questions. No, I intend this to be just a practical demonstration of some of my DCC installations.

    Hopefully, you may be encouraged to have a go with that difficult loco!

    So, let’s start with a Heljan Western I had in recently:

    Heljan Western

    The installation requires independent control of white & red lights & cab lights.

    The decoder used is a ZimoMX695KV with sound from Digitrains (code:ZS52D)

    I utilised the unique Zimo “Swiss Mapping” (SM) procedure to control the lighting.

    The wiring to the decoder is as follows:

    As you can see from the diagram, I also connected the Route Indicator box lights to the same Function Output (FO) as the white lights, so they work together.

    The reason I used FO7 to F10 for the Red Lights is due to the layout of the connections on the decoder. I wanted to avoid the Heljan wiring needing to be extended (see below regarding positioning of the decoder)

    The Swiss Mapping configuration below enables white lights to work with F21, red lights with F22.
    So, if F21 is engaged, white markers at the 'front' will be illuminated, direction dependant.
    And if F22 is engaged, red tail lamps at the 'rear' will be illuminated, direction dependant.
    For light engine, engage both F21 and F22.

    Swiss Mapping Group 1 (White Lamps & Route Indicator Box)
    CV430 = 21
    CV431 = 0
    CV432 = 1 – A-end white lamps & A-end indicator box lamps
    CV433 = 0 –
    CV434 = 7 – B-end white lamps
    CV435 = 0

    Swiss Mapping Group 2 (Red Tail Lamps)
    CV436 = 22
    CV437 = 0
    CV438 = 2 – B-end red lamps & B-end indicator box lamps
    CV439 =0
    CV440 = 8 – A-end red lamps
    CV441 = 0

    Cab lights are independently controlled with F23 & F24, and are not influenced by direction of travel, so can be switched on & off at will.

    Swiss Mapping Group3 (Cab Lights A-end)
    CV436 = 23
    CV437 = 0
    CV438 = 9– A-end Cab Lights
    CV439 =0
    CV440 =9 – A-end Cab Lights
    CV441 = 0

    Swiss Mapping Group4 (Cab Lights B-end)
    CV436 = 24
    CV437 = 0
    CV438 = 10– B-end Cab Lights
    CV439 =0
    CV440 =10 – B-end Cab Lights
    CV441 = 0

    These CV settings can be done individually using your handset or better still using Decoder Pro under the Swiss Mapping Tab

    Procedure notes

    It is important to mark each end of loco – I wrote A & B on the flywheels and inside the body-shell.

    Lighting wires are fastened down with horrible Heljan Chinese Sellotape


    Separate the wiring into + & - indicated by where they connect to lighting board.
    Attach tags to each wire to identify them – I used Tamiya Masking tape
    Lights can be tested with small battery (eg 2 x AA).
    Remove lighting board


    Arrange decoder so that wires need not be extended.
    (Only one pair needed to be – see joint protected by yellow shrink-wrap in photos).
    That’s the reason it is positioned off-centre.
    Mount the decoder securely with screws onto Plasticard strips or similar, which are then fixed to frame. I used Aradite Rapid.


    The Fan

    I decided to have the fans to start when the sound is activated, so mapped Function Output 3 (where the Fan- lead is connected) to the F1 button, using DecoderPro.

    Note that the “normal” F-button for lights is not used.


    I replaced the lead & plug with some smaller plugs & sockets bought from Ebay – it is simple to remove the original & solder a new one onto board (I once tried to buy some of theirs from Heljan – they wanted to sell me 10000!)
    I found that the fan works better on the 5v output of the decoder (see decoder diagram). It starts easier & runs slower


    The Speaker
    There is room in the removable tank space for a large speaker to be installed. Note the tanks are “handed”, so best to mark them.
    I used a Visaton SC4.7ND40 (approx. 40x70 mm.)
    I do not agree with the conventional wisdom regarding air-tight enclosures, but the speaker must be sealed to the front baffle. I used ordinary silicon sealant from Screwfix


    Motor & Pick-ups
    Connect as per diagram – don’t forget one end Red lead connects to the same socket on the decoder as the other end’s Black lead!

    It runs & sounds good. Everything works as it should!


    pricei, auld_boot, 3 LINK and 10 others like this.
  2. John K

    John K Western Thunderer

    Hi Tim
    I have done about as many as you have and I've put decoders into a wide assortment of models - 95% 7mm.
    The Zimo 69x sound decoders are my weapons of choice with the biggest speakers I get in.
    All programming is done with JMRI Decoder Pro via a Lenz L1USB Ethernet.
    I look forward to seeing more of your projects.
    John K
  3. Dan Randall

    Dan Randall Western Thunderer

    Hi Tim

    It's good to see you sharing your knowledge with a wider audience and I look forward to further posts as and when. I was actually going to ask your advice on a DCC matter at Telford, but wonder if you wouldn't mind answering here instead?

    When building a loco kit, it's obviously important to get it running well on DC, before embarking on the actual DCC installation, but how would you go about allowing for the later DCC installation please? (I'm building a kit as a commission at the moment and am thinking miniature connectors between the pick-ups and motor, that would then allow a decoder (fitted with the same male/female connectors), to be easily plugged in between once the initial DC testing is deemed OK).



    3 LINK and daifly like this.
  4. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Hi Tim

    Nice start, interesting to see other approaches to DCC installations.

    As it happens I'm experimenting with speakers and have a pair of Tang Band T1 1931S to install in a loco. What's your view on wiring two 4 Ohm speakers in parallel?

    And talking of speakers, have you used the Visaton SC5.9 ND 4 Ohm speaker at all. If so what's is low frequency response like?
  5. richard carr

    richard carr Western Thunderer


    This is all really useful, installing decoders can be a real pain.

    Until recently I have generally used Loksound decoders, but I have to say that Zimo 645 series decoders are excellent and can be used in Heljan models if you remove one of the motors.

    I look forward to reading more.

  6. Ressaldar

    Ressaldar Western Thunderer

    Hi Tim,

    great work, Zimos are my preferred choice so your posting will be become my source of reference.

    I look forward to the next 'episode'


  7. 3 LINK

    3 LINK Western Thunderer

    Good morning Tim,

    I must say anything DCC is a grey area to me, so having you show us and including photos and your own invaluable tips, will be very well received by myself and many others I'm sure.



    Ps, see you at Telford.
  8. Pannier Tank

    Pannier Tank Western Thunderer

    Hi Tim,

    Excellent article, thank you for sharing.
  9. Ian_C

    Ian_C Western Thunderer

    Very interesting. I'll keep an eye on this thread. One comment - there's a lot more space in a typical diesel loco than a steam loco. I'd be interested to see a steam loco installation if you get the urge.
    Dan Randall likes this.
  10. Steph Dale

    Steph Dale Western Thunderer

    Not in parallel. That drops the impedance to 2ohm which will be a bit low for most decoders. In series, with an 8ohm total load you should be okay.

    Tim, Sorry for the interruption!

  11. TheSnapper

    TheSnapper Western Thunderer

    Thanks for all you encouraging comments – much appreciated.

    Dan – Yes, really important to get smooth running on DC!

    Regarding planning for DCC installation, personally I would avoid using connectors. They have a tendency to come apart, unsoldered or just get disconnected. Wire-up as normal, but leave room for the bits, preferably all on the chassis, as it is easier to test if it’s all together. When connecting the decoder, it’s easy just to unsolder the pick-up wires from the motor & “insert” the decoder in between. A common irritation I see is the use of wire that is too thick and inflexible, necessitating a full rewire. Modern motors such as Maxons & Canons do not need to be fed with what looks like mains-grade cable!

    For most 7mm models fitted with highly efficient motors, you can use 00/H0 size decoders. For heavy twin-motored Heljan diesels, you need a big XL size decoder, unless, as Richard suggests above, you remove one of the motors. I have done that successfully.

    There are several companies providing suitable non-sound decoders, but for British sounds you really only have 2 choices, Zimo or ESU/Loksound, with “projects” available from various well-known suppliers. Choosing which sound to use can be a pain, especially if no prototype exists, for example, for pre-grouping locos. The it has to be the subject of research, much discussion then best guess!

    It’s possible to locate the speaker in a hollow boiler if necessary, but, please, never in the tender!. Speakers come in all shapes & sizes. Here’s some of my collection

    SpeakerBox (Medium).jpg

    Here’s one of the excellent Zimo Cube Speakers stuck to the chassis of an LMS Crab I did recently. They sound remarkable for their size:
    Crab (Medium).jpg

    Difficulties can arise with resin boilers or boilers full of lead or other ballast. Oh, and inside motion. Here’s a Cambrian 0-6-0, I did recently. Everything bunched together with a stay-alive unit stuck to the firebox roof! And another thing – it has a live chassis, which is a bit unforgivable in this day and age, I think:

    Cambrian15_1 (Medium).jpg
    Cambrian15_2 (Medium).jpg Cambrain15_3 (Medium).jpg

    Dave – as Steph says - NO – don’t do it! 2 ohm impedance is too low – maybe a Krell amp could cope, but I think you would be asking for trouble with a DCC decoder.
    I’ve not used the Visaton SC5.9 ND.

    I am currently trying out some EM2 “Earth Mover” speakers from DC Kits (Charlie Petty & Legomabiffo). Initial impressions is OMG - they definitely need to be fastened down securely!

    EM2s (Medium).jpg


    dibateg, Rob Pulham, daifly and 4 others like this.
  12. Dikitriki

    Dikitriki Flying Squad

    Of course having spent 35 years building O gauge kits, I have a lot of legacy live chassis models to deal with....including the Finney Duchess recently (nearly) completed. I was most surprised that didn't need a rework on the pick ups. Nowadays, I would be content to do tender pick up only, or dabble in R/C.

  13. Dan Randall

    Dan Randall Western Thunderer

    Hi Tim

    Thanks very much for the advice and for mentioning the fact that even in 7mm, you can sometimes get away with a decoder aimed at smaller scales.

    The commission build I'm working on is a Connoisseur 02 and will utilise a Mashima motor recommended and supplied by Jim McGeown, so I think that should qualify. Some further advice on the finer wiring you mention would be appreciated though (if you wouldn't mind), so I can hopefully obtain some at Telford. :thumbs:


    Last edited: 22 August 2017
  14. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Hi Tim.

    Those Earth Movers look very much like the Tang Band speakers I'm starting to use. And yes they are good.

    What are the dimensions as the ones around 88x36x14mm have a response range of 105Hz to 20KHz.

    So far I have fitted a pair of Tang Band T1-1925s in a GP9. My Dash 8-40B will have a larger version.
  15. TheSnapper

    TheSnapper Western Thunderer

    Hi Dave

    I think my "Earth Movers" are definitely the same as your Tang Band T1-1925's.
    Very interesting product line - I'd like to try the larger ones!
    Is there a UK distributor or do you have supplier details?

  16. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Hi Tim

    I ended up ordering mine from Parts Express in the US. However one parcel was taxed and the other wasn't!

    There appears to be no UK supplier but have found these guys on mainland Europe mentioned on some HiFi forums.

    Europe Audio VOF trading as Loudspeaker Freaks. Moriaanseweg west 97, 3222AC, Hellevoetsluis, The Netherlands
    TB speaker Modules | Loudspeaker freaks

    These are an Italian company. AUDIOKIT, Via Giuseppe Di Vittorio 37/39 Aprilia 04011, Italia.
    Speakers Modules - Audiokit

    Blue Planet in Germany band&pgNr=4

    I have a Tang Band T1-1828S, T1-1931S and T1-1925s and are shown below in that order. All are 4 ohm and yes that is a O scale diesel in the background.
    Tang Band.jpg
    The best performer is obviously the 1828 but the 1931 comes very very close and I'm impressed with it. The 1828 response range is 78Hz -20KHz and the 1931 is 105Hz to 20KHz. I have also attached the specification sheets for these three speakers.

    I have installed a pair of Tang Band 1925s in my GP9 one from each speaker outlet on a Loksound L v4.
    222 GP9.jpg
    And was going to use the 1828s in my U23B. This may change having heard the smaller 1931s.
    U23B 014.jpg

    Penultimately, If you're at Telford I'll have these with me on the Guild Technical stand.

    And finally - apologies for the digression onto speakers :rolleyes:.

    Attached Files:

  17. TheSnapper

    TheSnapper Western Thunderer


    No Problem! Thanks for the info.

    I'll come & have a natter at Telford

  18. richard carr

    richard carr Western Thunderer


    Thanks for all the info on the speakers, I wonder if the big one will go in a JLTRT 47 ?

    Dog Star likes this.
  19. Dog Star

    Dog Star Western Thunderer

    Just because you have one and others are still waiting...
  20. Dan Randall

    Dan Randall Western Thunderer

    Are they actually available yet?