Installing a DCC decoder in a Lima Class 67 Loco
   
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Last updated 21 December, 2017

 

The Lima Class 67 is very different to the firm's other diesel and electric models and requires a novel approach to fitting a DCC chip. Heralded as a major step forward in the quality stakes, it unfortunately turned out to be nothing more than a major step forward in pricing. The mechanism is a cheap and flimsy affair, undeniably better than Lima's previous efforts, but only because they were the lowest of the low. The reason for this preamble is that when fitting a DCC decoder you'll have to contend with some of the results of Lima's obsession for profit maximisation at any cost. The most obvious example of this is the fact that although there is a crude representation of a DCC socket present on the circuit board, the loco isn't actually DCC-Ready - it won't work unless you modify the board itself. The method shown here retains the Lima circuit board with the modifications needed to make it work, but quite frankly you could just as easily throw it away and hard-wire everything from scratch. Retaining the circuit board does, however, make it easy to swap decoders and experiment.

Decoder selection is certainly a little more tricky with this loco. Most of my favourites produced jerky, noisy running, something that many people have reported with this loco anyway. I found the best results were obtained using a Zimo MX61 decoder, but I couldn't bring myself to waste such a quality product in a downmarket loco like this. In the end I compromised on the next best performer, the Lenz LE1014E set in silent mode.

 

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All you need. The loco, a razor saw, a craft knife, a decoder with a standard NMRA plug (in this case the Lenz LE1014E) 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.

 

 

 

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The loco body is secured to the chassis by clips along the sides and a clip at each nose end. The black, lower part of the body is actually part of the chassis and the body needs to be gently prised apart along this line using the tip of a knife blade. Be careful not to mark the sides when doing this, and slip some bits of card into the gap as soon as it's wide enough.

 

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The body can be very difficult to remove because of the tenacity of the clips at the nose ends. I find it best to grip the fuel tanks and pull hard away from the body. A lot of force will be required, the chassis will bend alarmingly and various bits will fall from the inside. Don't worry about this as the Class 67 is famous for falling apart in the post anyway, reassembling them is almost a hobby in itself.

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With the body removed and any stray components replaced, you should be able to see what you're up against. To make future body removal a little easier you might like to shave the top from one (only one!) of the end clips - circled in red in the photo. The downside of this is the body won't be quite such a good fit on the chassis, so it's your call.

The lights fitted by Lima are quite dreadful, illuminating the whole body like a lava lamp, so now would be a good time to remove them. Snip the wires off where they join the circuit board, making sure you cut the right ones. All wires are thoughtfully colour-coded black, so double-check everything before making a cut. I prefer to fit replacement lighting, using either LEDs or the kits from Express Models but I'm not going to cover that here - this is just about fitting a decoder.

 

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If you have a close look at the circuit board you'll see eight holes that look suspiciously like they'll take a NMRA DCC plug. Don't be tempted to plug one in straight away as it won't work. There are 4 little solder tracks (I've ringed one in red in the photo) that will have to be cut away first. Note that the location for pin 1 of the decoder is at the bottom left in this photo, I've marked it for later reference.
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Using the tip of a razor saw blade cut through these tracks just enough to remove the solder and expose the plain board underneath. Brush away the debris and then make sure you've left none of the tracks in place to cause a short circuit . Once done you'll be able to plug in a decoder in the normal fashion, but as you've modified the circuit board it isn't quite as easy to revert back to straight DC should you change your mind in the future. Find a dummy plug from another loco, should you ever need to do so.
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Plug in your chosen decoder, noting that pin 1 (orange wire on the plug) is towards the centre of the loco.
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Secure the decoder using the supplied double-sided sticky pad, but keep it at the far end of the circuit board away from the plug, curling the wires in between them. The reason for this is there is very limited clearance in the plug area due to the exhaust silencer on the roof.
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In fact during running trials a terrific racket indicated that something was dragging on the drive system inside the loco. This turned out to be a diode (circled in red in the photo) being pressed against the flywheel. Being surplus to requirements once the lighting has been removed, the diodes could be discarded anyway, but I opted for another solution. As I didn't like the way the circuit board was rattling around loose I stuck a couple of sticky pads (sold in DIY stores to fix mirror tiles to walls) on top of the motor to push the circuit board up and secure it. I also made sure the cables and decoder were well away from this area to stop the roof pushing this end of the board down by pressing on the plug.

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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 clip the body back on, making sure the number 1 end (with the 'T' shaped exhaust set into the roof) aligns with the end of the chassis with the 2 round air tanks moulded on the side.

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

 

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