Some of the older Graham Farish N gauge diesels can also take DCC sound, and to a large extent, the process will
be the same as that described in the guide on Fitting
DCC Sound to DCC-Ready Farish Diesel.
However, there are a few complications to consider with the older models, which we will look at here...
Firstly, consider whether it is even possible to fit a speaker into the model - it isn't always possible to find
anywhere along the length of the chassis that has enough depth to get the speaker/enclosure in. YouChoos has successfully
fitted sound to Farish Class 50 and Class 44/45 Peak.
Once you've convinced yourself that it is possible to get the speaker in, then plan where the speaker, decoder and wiring
will need to go. The CT SL76 provides some more options over the SL75 because it is much smaller. For example, in the Class
44/45 Peak, the SL75 requires some grinding of the chassis to fit the decoder in flush, whereas the SL76 is thin enough that
you don't need to grind any special space for it.
The next challenge is how you will handle the pickups. Some models provide convenient screws and terminals that you can
simply solder the decoder's red/black pickup wires to. The Class 44/45 Peak generally has these, but not all of them do.
You may therefore need to tap some new screw holes into the chassis to achieve the same thing, or alternatively you could wrap the red/black
decoder wires around the retaining screws that hold the 2 halves of the chassis together. This is a simpler approach,
and although not as robust, will provide a good electrical connection!
The final challenge relates to the motor terminals, which are normally designed to press against the chassis itself to
gain electrical connection, which does not work for DCC at all, as you need to isolate motor from pickups. There are numerous
techniques available, including DCC Supplies' DigiHats, or simply grinding some space around the motor terminals so that they
do not come into contact with the chassis. With the grinding approach, you then reach the same starting point as described
for the more modern DCC-Ready Farish Diesels.
Here are some photos of a Farish Class 50 chassis, with grinding done for the speaker recess. Grinding to isolate the
motor terminals has not yet been done...
Below are some photos of a Farish Peak Class 44/55, showing where grinding has been done, and how the components have been located...
Note the major reduction in the height of the sugar-cube speaker's enclosure, and the shaping of the enclosure's top to match the profile of
the body. Also note the recess made in the chassis for a small capacitor - this is particularly useful with the SL76 decoder, to help reduce
crackles in the sound performance.
Grinding around the motor terminals is very clear here, and it is vital that there is a safe space between the terminals and the chassis
or you'll end up frying the decoder very quickly! Also note just how thin the SL76 is, as it sits above the motor - no other sound decoder
gets close to this kind of profile!
You'll also see below how cab lights have been added to this example. These are super-bright white SMD LEDs glued inside the cab, facing upwards.
They must be fixed low enough away from the cab roof that the light from them is able to reflect back down from some kitchen foil glued to the cab roof,
ensure that the gap is enough that there is no way the LED can short out on the foil.
Just to top this example off, we have 8 nano LEDs fitted for directional head/tail lighting! These LEDs are miniscule measuring something like
2x1x1mm. Quite fiddly to solder wires onto, and difficult to glue accurately into place so lots of pateient. Tiny holes are drilled carefully through
the body with these LEDs super-glue in behind. We have 2x red and 2x white at each end. To make it easier to squeeze the wires into place when
reassembling later, we have used a Dremel to route a shallow indentation along the inside of the plastic body - the wires are then glued into these
ducts, flush with the body, and electrical tape covering them before the body goes back on, to avoid snagging and stripping of the wires.