Installing a DCC decoder in a Bachmann Class 37 Loco
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Last updated 31 March, 2020


This is almost as easy as it gets - Bachmann have made their Class 37 DCC-Ready which means you can just plug a decoder straight in. No soldering is needed, in fact no tools at all other than the cross-head screwdriver you need to remove the body from the chassis. There isn't much of a need for these instructions, either, they're just here to show those thinking about taking the plunge how easy it can be. There are a couple of wrinkles, however, so read on...


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All you need to install a decoder into this loco is a cross-head screwdriver, a decoder with a standard NMRA plug (in this case the Lenz LE1025E) and the double-sided sticky pad supplied with it. If your loco is brand new like this one then it's probably a good idea to test-run it before proceeding in order to check everything is OK.

An equally suitable decoder is the TCS DP2X-UK which is a plug in decdoer with no wires.

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To be honest the most difficult part of some conversions is persuading the body to part company with the chassis. Not so here, Bachmann have sensibly joined things together with 6 screws that can be found in holes underneath the chassis. Undo these screws (circled in red in the photo) with a cross-head screwdriver and put them to one side - you may have to turn the bogies a little to get access to the holes holding the outermost screws. Bachmann lose a point here for poor design, as these 4 outer screws sit almost directly underneath the rear of the sprung buffers. Be careful not to damage the flimsy plastic when wielding your screwdriver!

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Once the screws are removed the body should come away with ease if you put the loco back onto it's wheels and lift. If not then just grab hold of the fuel tanks underneath the loco and lift the body once again, but don't pull too far as it's linked to the chassis with two sets of wires that supply power to the lighting units. Disconnect these two leads (they use a simple plug/socket arrangement) and put the body to one side. You should now have unrestricted access to the circuit board where you'll plug the DCC decoder. For later reference the front of the loco (or number 1 end as it's known) is the end with the crew figure in the photo and the equivalent end of the body is that with the large grille and fan in the roof. After the conversion your loco should move in this direction when you tell it to go forwards, but note that Bachmann lose another point for labelling the circuit board 'REAR' at this, the front end. Ignore this for the time being, there's a quick and easy fix for it later.

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A close up of the circuit board shows the light brown coloured dummy plug fitted to the DCC socket. Just pull it out and you will see the actual socket (the black thing with 8 silver holes in the inset photo) where the DCC decoder will plug. Keep the dummy plug somewhere safe just in case you ever want to convert the loco back to conventional control.

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My two favourite decoders for general purpose use these days are the Lenz LE1024E and LE 1025E, shown in the picture. These have Back EMF built in to give more refined running and can be had for well under £20 each including the famous Lenz 'goof-proof' no questions asked warranty. To confuse matters a little there are also versions available without the plug (LE1024A and LE 1025A) but the quickest way to convert this loco is with the plug versions pictured.

*Since this guide was first written by Steve a number of alternative suitable decoders have come onto the market from a number of manufacturers but the easiest to fit into this loco is the TCS DP2X-UK which has Back EMF and no wires.

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Either the LE1024E and LE 1025E will fit easily inside the loco, but the thinner, single-sided LE1024E will protrude a little too far into the cab area and make access to the bogie-retaining screw difficult in the future.

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The LE 1025E is a shorter, double-sided version of the LE1024E and is a better fit in the Class 37. Note how the hole containing the bogie-retaining screw is still visible in the photo. Fix the decoder in place with the supplied sticky pad and plug it into the black socket as shown. Bachmann have marked pin 1 on the circuit board and the corner of the plug with the orange wire should line up with the '1' on the board. If in doubt consult the photograph, but you won't blow anything up if you get it the wrong way round!

Strictly speaking that's all you need to do, the body can be replaced and the loco is ready for service. But there are a few additional options worth considering before screwing it back together:

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Although a nice, smooth runner, my sample tended to flash it's rear lights intermittently for no readily apparent reason. This first happened on the DC test track and I hoped it would 'go away' once the DCC chip had been fitted, but no such luck. So out with a suitable snipping instrument and remove the little orange capacitor on the main circuit board shown in this photograph....

Click here for a larger picture any more you can find tucked away by the side of the motor. Quite why Bachmann wanted to fit two on this side....
Click here for a larger picture one on the other side I have no idea, but their removal cured my flickering lights problem on both DC and DCC. If you just snip them off as I did, make sure no stray pieces fall inside the loco where they might cause a short circuit or jam something.
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Bachmann haven't bothered to provide red rear lights on the Class 37, something which I find quite annoying on a loco of this price in this day and age. My first thought was to solder in some red LEDs to fix this, but it's not quite as easy as it looks. The 4 plastic pillars that accept the body retaining screws are close behind the locations for the lights and this doesn't leave a lot of room for manoeuvre with normal sized LEDs. I think I'll wait and see if Rob at Express Models comes up with replacement boards using his normal, tiny, surface mounted LEDs....
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Before putting the body back on the chassis it's as well to check that everything is working. The safest way to do this is to plug the lighting wires back in, perch the body on top of the chassis and put the loco on the programming track. Try and read information from the decoder - the instructions for your particular DCC system will tell you how to do this. If all is well (and I've never yet had a problem) then pop the body back on and secure it with the 6 screws. Be very careful that none of the wires foul anything such as the holes for the screws. The wires and plugs for the lights are particularly tricky to get back in, so take your time.

Finally, as I mentioned at the start, Bachmann have made a pig's ear of wiring the loco up, with the result that everything is back-to-front. If you're not too fussed about this then it's not a problem, but if, like me, you want forward to be the number one end of the loco, then a quick fix is in order. Set bit 0 of CV 29 to 1 and the loco will go in the correct direction - see the manual of your DCC system for information on how to do this.

This guide first appeared on the ElectricNose web site belonging to Steve Jones and is reproduced here with his permission


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