Installing a DCC decoder in a Lima Class 31 Loco
   
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Last updated 25 April, 2014

 

The Lima Class 31 is typical of most older generation diesel or electric models in that it's not DCC-Ready. The decoder needs to be hard-wired in, but it's an extremely easy job and there's acres of free space, so no finesse is required. The loco is also typical of older models in that it has a very poor mechanism giving, at best, mediocre performance. The running of Lima locos improves tremendously if you fit a Back EMF decoder such as the one used here - accept nothing less!

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All you need to install a decoder into this loco is a small piece of circuit board, a decoder (in this case the Lenz LE130, ancestor of the current LE1025A) and the double-sided sticky pad supplied with it. Also you'll need your soldering outfit and a craft knife or wire stripper - not pictured because they're not very photogenic! If your loco is a new one then it's probably a good idea to test-run it before proceeding in order to check everything is OK.

 

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The body is fixed to the chassis by three tabs on each side and isn't difficult to remove. You can make life a bit easier by inserting pieces of cardboard between the body and chassis if you like, but if you pull the body sides outwards you should be able to wiggle the chassis free without much difficulty.

 

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There you have it, the separate body and chassis with huge amounts of space for fitting a decoder. Note for later reference that the motor is at the rear of the model and the front of the loco (number 1 end) is that with the circular radiator fan in the roof.

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Remove the power bogie from the chassis by twisting and pulling. Unsolder the square, white capacitor and all of the wires. Throw the capacitor away - they are surplus to requirements with DCC and should always be discarded.

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Solder a red wire to the pickup connection as shown in the photograph. The wire need to be long enough to reach the decoder at the other end of the loco so be generous - you can trim it to length later.
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Solder a similar length of orange wire to the left hand motor terminal and a grey length to the right hand one. Replace the power bogie in the chassis and make sure it's free to turn without trapping any of the wires.
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For convenience I prefer to solder all wires to a small piece of circuit board cut from Maplin product code FL17T. I find this makes it easier to swap decoders or fit lighting at a later stage, but you can just solder the pickup wires to the decoder wires and wrap them in insulation if you wish. Solder your red wire from the power bogie to one track on the circuit board. Solder Lima's black wire from the central brass tag to a different track. If you're lucky enough to have one of the more recent Lima models with pickups on both sides of the unpowered bogie then you'll see an additional black wire coming up through a hole in the floor. Solder this to the same track as the red wire from the power bogie - see the photo for clarification.
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Now solder your orange and grey wires from the power bogie to two separate unused tracks on the circuit board. You should now be using four tracks - two for power from the wheels (red and black) and two for the power to the motor (grey and orange) if all has gone to plan. Double-check against the photo but note that you might have a second black wire connected to the red track just to confuse things!
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Now solder all eight wires from the decoder to the eight tracks on the circuit board. Match black to black, red to red, grey to grey and orange to orange as in the photograph. The other four colours are spare and can be soldered to any of the remaining tracks - you might need them if you ever add lights to the loco. There is actually a ninth (purple) wire on this decoder which I just left hanging free, but I could have soldered it to another track on the circuit board had I wanted.

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Stick both the decoder and circuit board in place with double-sided sticky pads. Try and make a better job of keeping the wires tidy than I have in the photograph - tape them down to prevent them becoming trapped between the body and chassis.
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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 put the loco on the programming track and 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, taking care not to trap any wires between the body and chassis. The number one end (with the radiator fan in the roof) goes at the opposite end to the power bogie and should be at the front when you tell the loco to move forwards.

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

 

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