At first sight it looks almost impossible to fit a DCC decoder to the J94 loco without it being visible but it is easier than you might think.
I did consider fitting it in the cab roof but the leads would have been visible through one side of the cab cut-out and door. If the loco is only going to be seen from one side this would be acceptable but from lower viewing angles the decoder would be visible on both sides.
To my surprise it is possible to make room for the decoder in the smokebox without removing any metal from the chassis. But you do have to remove metal from the body but this seems to me to be less of a risk.
Firstly the chassis needs to be modified with the insulated bottom brush holder and clip available from Gerry Spencer. I generally file a chamfer on each rear edge of the recess for this brush holder and file the rear edge itself to make sure it is clear of the clip. The chamfer allows the decoder lead to clear the rear wheel. Cut the capacitor lead that is crimped into the chassis leaving a tail on to which you can solder the decoder lead. Cut or unsolder the capacitor from the upper brush wire. Cut the wire from the upper brush to the chassis clamp nut and bolt leaving a tail at each end.
The decoder will fix to the front vertical face of the metal chassis using double side tape (not the fixing pads supplied with the decoder, they are too thick) with the large chip facing the chassis. Cut and solder the leads, black to the chassis clamp bolt, red to the tail left by capacitor, orange to the lower brush clip and grey to the tail on the upper brush clip. Cut back and insulate (or completely remove) the blue, white and yellow leads. I have a feeling no-one is going to come up with a lighting kit for this loco but you may at sometime want to reclaim the decoder for another project.
Test!
A little magic tape or similar on the front of the decoder will insulate it from the body and some more tape will keep the leads tidy.
Test again.
Easy so far, now comes the hard bit. To make room for the decoder the vertical metal bar connecting the footplate to the inside top of the smokebox/tank need to be removed. First push out the plastic smokebox door. With a dentist’s bur or similar in a mini drill grind out the bar. Then grind out the footplate area within the smokebox. A guide is to remove metal as far as the rear of the projection that goes into the coupling socket on the plastic part of the chassis. Carefully grind out material inside the top of the smokebox. A piece of card the size of the decoder plus the bent over leads can be used as a test template. When you think you have enough metal removed try to remove just a little more and then very carefully test fit the chassis.
If it fits put it on your programming track to check there are no short circuits.
Now you must remove material from the inside and rear face of the plastic smokebox until it is a snug sliding fit over the decoder and fitted flush with the front of the tank.
And that’s it. It would probably be easier to use a milling machine to modify the body but as I don’t have one …………..
I might soon try to fit a TCS M1 decoder to this loco but despite the adverts it is slightly longer that the Lenz 0521 because of the plastic sleeving and the way the leads are attached. It should be possible to fit this decoder even if it means making a recess in the plastic chassis keeper plate. The advantages of this decoder are the “dither” slow speed feature and the ability to program half and full speed CVs.
Watch this space!