Keith M's workbench. Fitting a DCC decoder to a "Not DCC ready" model.

Discussion in 'Workshop Benches' started by Keith M, Nov 7, 2019.

  1. Keith M

    Keith M Staff Member Moderator

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    I suppose setting up a'workbench' thread is something I ought to have done ages ago after quite a few of my "How-To's" which might have been better under this heading, still, better late than never Eh? Since we have a few recent members, some of whom have ventured into DCC control, but not yet plucked up the courage (or gained the knowledge) of how to fit DCC decoders into loco's, having recently bought a used Bachmann "Austerity", I though this might be a useful time to explain the process. As it happened, I initially thought that this locomotive (an Ebay buy for £63) was the current version which has a 21 pin decoder in the tender. On examination after it arrived, it was apparent that it was one of the earlier "Not DCC ready" versions, but as not everyone has the means to go out and buy the latest brand new off the shelf models (I can, but I'm er how shall we say, 'Careful' with money!), many may be considering buying used, either via dealers or perhaps Ebay. This isn't really a problem assuming the loco is "As Described", and I'd always advise checking it immediately on receipt, preferably on a DC supply, but failing that, even a 9 volt battery, to ensure it does what it's supposed to do. If all is well, then it's time to go about fitting a decoder. Quite often, if the loco has been looked after, you'll often find the original instructions in the box, and this can be useful as there are usually not only lubrication point information, but also instructions on how to remove the body from the chassis. This can vary widely, from just easing the body sides away from the chassis as you lift it off (Quite a few diesels have this method) to a number of screws which need removing, often under bogies or trailing trucks. If there is no such information, then you can often find the answers on either Google, U-Tube, or just ask on the forum, as someone will doubtless be able to help. This was the case with my model, eventually discovering 3 screws that needed removing. With that done and the cab handrails released from the body holes, the body was eased off to reveal the gubbins.

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  2. Keith M

    Keith M Staff Member Moderator

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    So it was apparent that the best way forward was to remove the small motor mounted circuit board which would easily create enough room to fit a small DCC decoder taped to the motor top. I prefer a simple tape securing as if you glue it and ever need to remove the decoder, it means more work. Anyway, two tiny self-tapping screws and the board and it's plastic spacer below it is now free floating.

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  3. Keith M

    Keith M Staff Member Moderator

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    Now it's time to get rid of the board itself, so out with the soldering iron, unsolder the pickup connections, then the one's from the motor. I'd suggest you mark (felt tip pen will do) the motor polarity (Red/Black usually) so that you get the connections from the decoder the right way round, Orange to what was the Red connection, Grey to the originally Black one, and with the junk out of the way, we can then start to put things together.

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  4. Keith M

    Keith M Staff Member Moderator

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    It's best to fix the decoder in place at the start rather than have it flapping about on the wire ends whilst you're trying to solder things up, so using 'Kapton' tape (which is a kind of electrically insulating 'Sellotape'), fix it to the motor top, wires towards the rear, away from the drive worm. My usual 'Decoder of choice is the 'LaisDCC' one, Chinese made (isn't everything these days?) and cheap but fully functional. This particular one is a 2 function + motor, which is more than enough as I only need it for motor control, it comes as standard with "Stay-alive" connections, which I don't need, so I cut off the White and Yellow (function) wires from the end with input and output wires, and as I don't need the "Stay-Alive" function, the Blue and Black wires from the other end of the decoder were removed also, as close to where they exit from the decoders pvc sleeve, so as not to short out on anything. This leaves only the 4 wires needed, Red/Black from the pickups, Orange/Grey to the motor. We need to keep things as small as possible as there's not acres of space between body and chassis. The ruler gives an idea of decoder size.

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  5. Keith M

    Keith M Staff Member Moderator

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    So with the decoder stuck in place, it's time to wire it in. Very simple to do, as you can see. Make sure wiring is kept as short as practicable, you don't want it wrapped around any moving parts, and any 'in-line' joints, insulate them preferably with a suitable 'heat shrink' sleeving, you can always add a bit more tape to hold errant wiring!

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    At this point it's time to program the decoder. I have a 'Rolling Road' which is very useful (Also handy for 'Running-in' any new loco on DC before conversion). If all is well, then it's time to put the body back on, making sure not to trap any wires. Note that the springy looking black wires to the rear of the chassis are actually the loco's cab handrails which will be clipped back in place when the body is fitted.
     
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  6. Keith M

    Keith M Staff Member Moderator

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    With everything back together, a final test to ensure the loco runs ok with no trapped wires etc, from then on it's a case of sit back and enjoy your 'new' loco (And give yourself a pat on the back if you've just achieved your first conversion!). Any questions, just ask and I'll do my best to help.
    Keith

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  7. Kimbo

    Kimbo Staff Member Moderator

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    Nice conversion Keith. I’ve done a couple the same way. The sound conversions are a bit harder, you just need to route all four wires back into the tender.
    :tophat: Kim
     
  8. SRman

    SRman Full Member

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    Converting the Bachmann N class 2-6-0 involved much the same ideas, except that these have a vertically mounted motor in the firebox. I got rid of the pcb and wired the decoders into place just as Keith did with the Austerity. The N requires physically smaller decoders though. My earliest one used a Digitrax DZ123 which does not have BEMF control. I will replace that, one of these days, possibly with a small Zimo decoder if I can get one. The second conversion used an improved version of that decoder with BEMF, a DZ125. The last one I did used a TCS M1 decoder, which was the best one to date.

    Note that current Bachmann N's have a 6-pin interface. I have a feeling Bachmann have updated the Austerities too, possibly to a 21-pin interface.
     
    Last edited: Nov 8, 2019
  9. Keith M

    Keith M Staff Member Moderator

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    One or two of my steam sound conversions also have the speaker in the tender as Kimbo mentions. It's often difficult enough to find space in a steam loco body for the decoder so the tender, bunker if not a tender loco, or as a last resort, in the cab is usually the only other option. I recall fitting a sound decoder into my Bachmann E4 loco which despite allegedly being "DCC Ready" didn't really have enough space, so removal of the socket, wiring and cutting a small area of chassis away was necessary, then hard-wiring, though you may need to be brave (or slightly mad) to do that with a new loco. Earlier 'Split-chassis' Bachmann loco's can also be DCC fitted, and I've done several, although they are generally a little more difficult, but certainly not impossible, and both SR Man and myself have DCC converted the Bachmann Wickham Trolley, which Bachmann themselves describe as 'Not DCC convertible.' As yet, I personally have not come across a model that is not DCC convertible, wether or not a model is worth converting is down to the owner though.
    The later Bachmann Austerities do indeed have a 21 pin decoder in the tender, and presumably have provision for speaker fitting too. At least manufacturers are beginning to realise that many modellers want the option of sound fitting and are providing for it in the design.
    I have a couple of DJ Models (no longer with us!) loco's which have provision for a 6 pin decoder in the boiler. Removing the magnetically held smokebox door reveals a pull-out harness, all that is required is to unplug the DC plug, fit a 6 pin decoder, push back the harness, refit the smokebox door and that's it, job done.
    As an aside to this, anyone 'New' to working on loco's, even just for lubrication, will find it much easier if you make up a simple cradle comprising 3 suitable pieces of wood in the form of a trough, dimensions to suit the gauge of loco you're working on, with a lining of foam or similar sufficient to hold the loco body gently but firmly in an upside down position. Tasks such as body screw removal, wheel cleaning etc will be made much easier, and the cradle need not be anything too elaborate. The final thing to remember is that you MUST make sure that the decoder output is electrically isolated from the loco chassis or any other conductive metal part, otherwise your decoder will likely be instantly killed, possibly an expensive mistake. In this regard, it's not a bad idea if you embark on a sound decoder installation, to try a (much cheaper) non-sound decoder in place first, better still, invest in a cheap multimeter, and do continuity tests first to ensure no short circuits.
    Keith.
     
  10. SRman

    SRman Full Member

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    Like Keith, I found the Bachmann E4 to be too tight to just fit a decoder and speaker as is. I also had to remove the socket and a little metal to create a flat bed for the decoder and speaker. Using a Zimo MX648 and a sugar cube speaker with a rounded top from YouChoos allowed me to sit the speaker directly on top of the decoder, with both sitting inside the boiler barrel ... just!

    As Keith said, there are very few models that can't be DCC fitted, but adding sound can be more of a challenge.
     
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