Graham Farish N Gauge Class 37 with Zimo MS Sound

Kit: MS480; SugarCurve8; 2x 470uF Tall Tantalums, 2x micro cab light LEDs

For this installation we are going to revert to our older method, so rather than using the drop-in MX660 sound decoder, we want to use an MS sound decoder instead, so we choose the MS480, which is the replacement for the MX648. This has 6 full power function outputs available, so will drive headlights, taillights and cab lights all independently.

The model is totally disassembled, and just the plastic bits put back in so that we can milling space for a larger speaker - a SugarCurve6 could have fitted without any milling, but the 8mm version will sound better with more bass response.

With the speaker platform milled, we clean the chassis up and reassemble with motor and bogies, soldering orange and grey wires directly to the motor terminals before we clip it back together.

Here are a couple of photos of another model, perhaps slightly neater milling - we didn't need to go quite as deep as we did on the LoadHaul model!

Back to the LoadHaul 37, we lay down some electrical tape, and then thin double-sided tape on the speaker platform.

We want the speaker to sit flat, so we ping out the terminals, bend them back, and snip them short - this not only allows it to sit flat, but gives us more convenient tags to solder speaker wires onto.

By snipping the original factory PCB, we salvage the screw holes, to which we solder red and black wires for track pickup, and screw those into place.

Next to consider is the lighting. Our first job is to replace the lighting board wires with some finer and longer ESU decoder wire, in appropriate colours for DCC. In the centre is the positive, so that is blue. We use white wire for the white LEDs and yellow wire for the red LEDs.

The MS480 decoder will put out rectified track voltage for the lighting outputs (normally around 12V), so we need to include some resistors to protect them. The original Farish PCB would have had these on, but we're doing away with that. We snip part of the Farish PCB and add a couple more resistors so we have 4... the Farish board probably only had 2 because it didn't have cab lights, but conveniently there are solder pads for 2 more resistors!

One side of the bank of resistors is joined, so we must do a bit of experimentation to work out which side that is, and once established, we solder an old resistor leg across that entire side to form a common point for the decoder's common positive wire. The other side of the resistors will go off the positive of the front lighting board, rear lighting board, front cab light and rear cab light. They must not share resistors, otherwise the lighting will be affected by each other (e.g. headlights may dim or go off if the cab light is switched on!).

Carefully crack out the cabs, and glue in a micro white SMD LED for the cab lights, and add a little fella each end while we are there. The cabs normally need a spot of glue to fix them back in, so be patient and careful lining them up exactly where they were originally.

So, onto the decoder, which we totally strip of its' wires because we will be using the finer ESU decoder wire for this entire job, as well as using more of the solder pads. The purple speaker wires go on first - we tend to attach the outer row's wires first, then the inner as it is easier to access them as you go.

Our stay-alive will be a pair of tall 470uF Tantalums (16V), which can be connected directly to the MS480 (up to 1000uF/16V can be attached directly without extra components), so this simplifies stay-alive installation compared to the older MX648 or MX660 decoders.

The methodical task of joining all the wires begins, making wires long enough to reach, but short enough that there isn't too much excess. Note that on the MS480, there are actually 8 function outputs, but FO3 and FO4 are only logic level, so we skip those and go for FO5 and FO6 for the cab lights. FO6 is a pad on the other side of the decoder - you can see a grey wire attached to the corner in one of the photos below.

A lot of care is of course required to do this - soldering directly to the decoder's pads need good skills and decent soldering kit, but being methodical and steady is the key.

All is done, and so we wrap the decoder in Kapton (there is electrical tape on top of the motor where the decoder will sit, then a blob of BlackTack holds the decoder in position. Wires are tied up and held down with Kapton tape. The results is excellent, and output from the MS is clearly higher compared to the MX decoders.

Please note that these guides are provided as useful resources for you, as-is. YouChoos cannot be held responsible for errors in the information, or for any damage caused to your models or equipment if you choose to follow any of the steps detailed here.