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If I want to have a layout controlled by DCC then there's one thing that cannot be avoided - fitting decoders to my fleet of diesels, DMUs and EMUs. This isn't going to be a walk in the park for 2 reasons. Firstly, seeing as I am into N Gauge, there isn't a lot of room to work with. Secondly, as you'll soon see, the old Poole-built locos which form the bulk of my fleet are not exactly DCC-friendly. I decided to convert my Rail Express class 47 diesel to DCC first of all.

The loco to be converted	The bodyshell removed

Lifting the bodyshell revealed that virtually the entire chassis block to be a solid metal block that forms one half of the power supply circuit to the motor! Isolating the power supply to the motor is not going to be easy. There are 2 ways that I can see to do this, one elegant but hard to accomplish and the other easy to achieve but easy to make a mess of the chassis and also having the potential to be a bit of an eye-sore.

The easy way would be to clip off the power pick up tab, solder the decoder input to the copper pick-up plate on the bogie and the output of the decoder to the metal chassis block. The main problem with this method is that, once done there would be no going back to DC.

The elegant way would be to remove the clip and brush guide on the underneath of the chassis block that connects to the motor, insulate them both, connect the output wire of the decoder to the clip and then fit them back in place again. The input to the decoder can then be secured somewhere on the chassis block. I tried converting an old chassis using the first method and it does work but I wasn't entirely happy with the result visually.

The insulated brush guide

Then I heard of a solution. A chap called Gerry Spencer - Gerry Spencer's website - does a DCC conversion kit for Poole-built class 37s and 47s. Osborn's Models keep some of these in stock so I ordered 5 kits as well as the drill bit needed. These arrived today - 22/10/06 - and they contain an insulated brush guide, an insulated clip with a wire soldered onto it to allow easy connection with the decoder output and some sleaving. The wire soldered to the tag is coloured orange which helps when connecting the output wire to it as you'll see later on.

The pack cost £7.75 which does appear a little steep on first consideration but when you think that a loco will set you back between £43 and £80 plus a decoder chip will cost around £20-30 for a decent one, on reflection paying £7.75 to do a neat job doesn't seem that expensive. Especially when you consider that it would be a relatively straightforward job to convert a chipped loco back to DC should you ever want/need to do so. I don't see a reason why anyone would want to but there may well be a reason to revert back to DC and this method of conversion does make it possible.

The preparation

The bogies removed	The top power supply distribution	The power supply capacitor

OK, once the bodyshell was removed I then removed the 2 bogies. The bogies are directional but determining which bogie goes on which end is made easy as a little spot of paint is normally put on one end of the chassis and on the corresponding bogie for that end. Sometimes this isn't done but, luckily for me, this particular loco wasn't the case.

Next to come off was the plastic top to the chassis. First of all I unscrewed the 2 screws that hold the pick up tabs and form part of the electrical circuit and took them off, being careful not to lose the nut or pick up tabs. Next I lifted off the clip that holds the brush and brush guide in place and put them carefully to one side as well. That left the plastic top to be simply lifted off. That was also put to one side and now gave me access to the motor. I took the capacitor out and placed that in a box. I did not intend to replace the capacitor when I re-assembled the loco as the supply would be AC rather than DC. A capacitor passes AC so this would, effectively, short circuit the supply if it was placed back in the circuit. I also put the copper bar to one side as I did not intend using that on the conversion.

The chassis with the top removed	The plastic top after removal	View of the clips before the bogies were removed

I turned the chassis over to get access to the clips holding the motor in place. These clips form round the motor, are guided in place by a couple of notches on either side of the chassis and held in place by a rather powerful - for it's size anyway - magnet. I took a small screwdriver and carefully prised up each of the clips, removed them and placed them to one side.

Next to be removed was the magnet. I needed to take care to remember which way the magnet went in as I believe it's directional. Luckily for me, there was a white mark on one side of the magnet so this made it easy for me to remember it's correct placement. I now turned the chassis back over in order to remove the motor. This needs to be done as the hole for the brush guide news drilling out in order to accommodate the insulated brush guide and it's not a good idea to drill the hole out when the motor's still in place. That's an open invitation to damage the motor!

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The hole for the brush guide before being drilled

There are several types of motor connector for Farish locos. In this case I had one where there is a plastic joint/connector half way down the motor arm. This made it easy to lift out the motor and put it to one side. I noticed that there were some scorch marks and carbon residue underneath where the motor sat so took the opportunity to give it a little clean.

Next I took the drill bit that I bought at the same time as I bought the DCC conversion kits and fitted it to my Dremel mini-drill. I did initially plan on using my pin vice but it wouldn't drill out the hole. The drill bit would become jammed in the metal and the pin vice would turn but the drill bit wouldn't. This made me a little nervous as one little mistake and I would ruin the entire chassis block. By being careful, though, I was able to successfully drill out the hole for the new brush guide. Finally, I gave the entire chassis block a little brush down to get rid of any dirt, grime and metal filings from the drilling.

Fitting the DCC conversion kit

The new brush guide fitted	The new brush guide top view

Now all the preparation work was done I could get on with fitting the conversion kit. First I took the old brush spring that was fitted to the underneath of the motor and fitted it to the new brush guide. This was all then placed in the hole that had just been drilled out in the chassis block. I was quite relieved to find that the insulated brush guide fitted the hole quite nicely and only took a small amount of pressure to get it to slip into the hole and in place. Next I took the insulated clip and tried to fit that in place. Unfortunately, the insulation on the first clip got caught on the chassis block and damaged it. I found this out after fitting it in place and then testing the circuit whereupon I was rather annoyed to find that the motor was still not isolated from the chassis. I took the clip off and found that the insulation had been torn while fitting the clip! Damn and blast.

I then took another clip and, this time, I teased the arms of the clip out slightly. This meant that the clip still clipped firmly in place but the insulation did not get damaged on the chassis. A new test of the circuit showed that the motor was now isolated from the chassis.

I then put the chassis back together by screwing the pick ups tabs and plastic top back into place. Several more tests with a digital multi meter showed that the bottom brush on the motor was fully isolated from the chassis.

Fitting the decoder

The Lenz Silver Mini decoder to be used	The decoder connected to the clip	The lead fed through the chassis

The decoder of choice this time was a Lenz Silver Mini. I do have a Gold Mini but will use that on a later conversion, possibly my Pullman class 73. Even though it's advised not to do this, I removed the bottom clip so as to aid soldering the decoder. I took the orange wire from the decoder and fed it through the chassis block. I then took the sleaving supplied and put that on the decoder wire. I did not trim the wires from the decoder as I wanted some play in the leads and I felt that there was more than enough room inside the bodyshell for the wires considering how thin they were.

Next I took the clip and soldered it to the orange wire of the decoder. I then moved the sleeving down so that it covered the joint and insulated it. The clip was then secured back in place and the circuit was tested once more to make sure the brush guide/brush clip was still isolated from the chassis. I was pleased - and not a little relieved - to find that it was. One wire down, 3 more to go.

Top power feed soldered	The decoder in place	The wiring done

For the top power feed to the motor, I decided to solder the grey wire from the decoder straight to the clip for the brush guide and brush. I did buy some solder tags from Maplin for this job but, even though I bought the smallest tags they could supply, they were still far too big for the clip. This left me with little option but to solder the wire in the way that I did. Unfortunately the clip was now a little loose but still made an electrical connection which was a relief. I'll have to look at resolving this issue at some stage in the future. The black power lead needed to be connected to the chassis. I took the simple expedient of undoing one of the bogie retaining clips, slipping the wire in and screwing the clip back in place. It may not be pretty but it did the job!

Before addressing the last power feed, I decided to secure the decoder in place due to the way I was going to do the last power feed. I simply cut away part of the plastic top, took the sticky pad supplied with the decoder, cut it to size, placed it on the chassis and secured the decoder to it.

I now did the last power feed. To do this, I got a short length of red wire, stripped back the ends, tinned them and soldered one end to the red decoder wire. I then took the 2 ends of the red wire, undid the 2 screws connected to the pick up tabs slightly, slipped the 2 ends of the red wire under each screw and then screwed them back down again. Finally, I trimmed back the white, yellow and blue wires on the decoder as I had no use for them. A final couple of tests of the circuit showed that the inputs and outputs of the decoder were fully isolated. I then tidied the wires up and replaced the bodyshell. It fit on perfectly which was a relief.

The loco now converted to DCC

The only thing left to do was to test the loco out on the circuit. This I did and the loco worked first time.

Well, for a while it did! I then tried to reprogram the loco and it promptly stopped working. I fitted a new decoder and this wouldn't work at all. There seems to be a problem somewhere but where I don't know. I think I'm going to have to do a bit of investigating. It would either be the main DCC set or, I suspect, the transformer I'm using to power the Lenz Set 100.