By Laurie McLean
Photos by the author
“She’ll be comin’ round the mountain when she comes,
And she’ll be sparkin lights and soundin’ when she hums,
She’ll be comin’ round the mountain, exhaust valves a shoutin’
She’ll be flashing her new markers when she comes.”
And the bells & whistles singing all the way………
Ahh…the absolute pleasure of sounds & lights in our little narrow gauge steamers makes all the
difference these days. They sure give pleasure, but working with all this DCC stuff can get a bloke a
bit lost, not like “a few kangaroos lost in the top paddock”, no, I mean in trying to understand what
goes where & more importantly WHERE to fit it all!
Right’o, I got a bottle of “Durango Wheat” & a full glass for starters next to me so here goes
explaining how a Soundtraxx Micro Tsunami sound decoder & a bunch of miniature LED’s (called
SML’s) were fitted into my PSC-MMI K-27 Class 2-8-2 Steam Locomotive.
The journey will be in stages and there will be pictures for those who are in the IT industry to
follow what’s happening – we are not going to use any symbols or computer lingo here!
Firstly, let’s understand what it is that we are going to do here.
We are going to be fitting a Micro Tsunami sound decoder & 4 x SML’s into a new Hon3
MMI K27 steam locomotive.
The 4 x SML’s will be fitted into the HEADLIGHT, both CLASSIFICATION MARKERS
and CABIN light. (Available from Richmond Controls – Jim’s a wonderful helpful man)
For starters we need to open up the locomotive removing the boiler from the frame so that we can
get to the motor. I won’t go into detail as to how to do this but if you can’t do this part – stop now!
On opening the MMI K27 we find a useless wiring circuit board & a set of wires with mini
connectors that run to the light bulbs in the headlight & in the roof of the cab – remove all of this &
put it away for that day in 25 years when you might find a use for it.
Now the real work begins (pour another “DW”).
We need to fit some extra pick-ups onto the loco because it’s the old fashion type without a “split
frame body – hmmmm……..one day PSC?
The extra pick-ups were made from phosphor bronze strip – 1/16’ wide by 0.005” thick & come in
a pack of 10 pieces 6 inches long from Slatters UK.
We are going to fit wipers to the first & last drivers on the fireman’s side (L/H side if your in I.T.)
OK, lets start with showing some pictures so it makes it easy –
FIG.1 As supplied from PSC MMI – rip it out!
I made a sketch that shows where the extra wiper pick-ups were fitted in FIG.2. These were made
using Clover House PCB strip & soldering the P/bronze strip onto the PCB allowing the P/Bronze
strip to “spring” against the back of the driver wheel. Make sure that when it is glued the solder pad
is clear of the frame – obvious short!
I used ACC to glue the PCB to the loco frame across the main cylinders casting & bent the
P/Bronze at right angles so that the end of the strip touched the stainless steel of the L/Hand driver.
DO NOT let the wiper touch the wheel casting as this is NOT insulated – the insulation is fitted
between the St/Steel tire rim & the driver wheel proper. You will need to check that there will be
no shorts as each step is completed – again check each step of the way & you won’t end up looking
for a problem & pulling things apart again – just do the checks please.
The best way to get the wipers touching the back of the tires so they absolutely clear & avoid any
chance of touching any part of the driver wheel or frame is to angle it across the tire on the tip back
edge. The wiper should have about 1/16” of its end away from the actual point of contact & just a
little bit of pressure – don’t worry, the wiper will wear out before the driver tire.
Now let’s look at the back wiper FIG.3. This was a piece of PCB on edge & glued to a piece of
styrene to doubly make sure of insulation protection.
You can see how a black #30 jumper wire has been soldered from the front wiper solder pad to the
rear wiper solder pad. I also used the existing black wire from the draw bar & soldered it too onto
the rear wiper (more the better for L/H pick-ups.)
You will have noticed the new piece of PCB on the side of the motor – if you haven’t stop drinking
& put the bottle away now!
This new PCB is a terminal & when the boiler body is replaced it will clear but we will be covering
this later.
Next we need to modify the brass bracket in front of the gearbox. This is where the original
supplied circuit board was. We need to straighten the front wing so it is straight & re-bend the rear
wing so it gently holds the Micro Tsunami. You can see the shape above in FIG.2.
Now, before we refill our glass, I presume that the loco ran perfectly before we started any work?
Was that a big yes? – OK we can keep going then – refill your glass with “DW” & mine too.
We have fitted 2 wipers & checked that there are no shorts using a multi-meter – good work so far.
The loco should be able to run without the tender because we have done this little trick.
FIG.4 shows the front lights of the K27 – this is what we are working on next.
FIG.5 shows the tiny SML being tested before installing into each Classification Markers & the
Headlight. Notice how small these are – mate! We are going to need another drink – make it a
To test the SML’s I have a LED Tester but you can use a 9v battery & a resistor to do this. Led’s
must have a resistor & the decoder wires for lights are:
WHITE for headlight
BLUE is common
Yellow for rear tender light.
We place the resistor on the BLUE wire.
Well it’s a little different here because we are fitting 4 LED’s be they SML’s they are still LED’s.
Well, for mine I used a 1k resistor on the headlight by itself.
For the markers & cab SML’s I fitted a 2.7k resistor.
Here she is in the cradle – need to treat her gentle.
From the photo above FIG.6 you can see the tiny wires that run inside the boiler. The Cab wires run
under the tape & join up with the 3 sets of front wires. There is room in the smoke box to COIL the
excess enamel wires – don’t cut them.
The SML’s are available from Richmond Controls
Fitting the SML’s into the Headlight is easy. The old 12v globe was removed by pulling it from the
hole under the headlamp. We need to protect the “pads” on the back of the SML so there is no
chance of a short. So, cut a small piece of styrene the same size as the SML pad & glue it to the
back of the pad. When this is dry glue the SML in the centre of the headlight – the styrene will
insulate the SML from the metal headlight casting. The headlight lens remains.
Now the tricky bit – fitting 2 SML’s into the markers.
How’s the bottle? Need to refill the glass? – Maybe its time for the next bottle & a fresh glass!
You do have a magnifying glass to look through don’t you? Well if you don’t you better get one
now because we’re going to need it. This is “brain surgery” in Hon3 & I’m only a lay witchdoctor.
Go FIGure
Take a deep breath & a big “swig” – here we go…………..
I cheated here & put my glasses on as well as using the magnifying glass.
Take a scalpel (Exacto blade) & begin to cut away any high paint spots on the BACK of each
marker casting – work with steady hand & wrap patient in foam.
These marker castings have a hole in front & in back – it’s the back where we are going to insert the
SML & we need to make sure it’s clean.
Remove a SML & ask the nurse for a pair of tweezers so you can grab the wires just at the solder
pad area. You should have it in your tweezers & can manipulate it into the back hole.
Does it fit? It should if it came from Richmond Controls. The shape is slightly rectangular & so is
the hole – try again, gently push a little, there ya go, it fits!
Well done, have another drink & steady your hands cause’ your only half done – more operation yet
Now do the next one, see, your starting to get the knack now. Well, now you can glue them in.
Jim at R/Controls recon’s its best to use some of the glue the airplane boys use on wings but
whatever you use remember you may one day want to remove the SML’s – your choice of glue.
No, you can’t use “DW”, it’s medicinal only.
I used ACC but that’s all I had at the time. The wires go thru the original hole in smoke box.
How the wires & SML’s fitted in Markers.
Run marker wires over bracket & into hole
Must be time for a refill………
Well, you’re now an honorary doctor of electronic genius having followed all this so far. Hang on a
bit longer & we’ll get you a degree towards the end.
This is bigger stuff – it’s called MICRO. The next step we will have lots of fun playing with all the
coloured wires.
Can you focus on the photo above? Was that a Yes? (You mustn’t have had as much as me then!)
Let’s get into fitting the Micro Tsunami. As you can see it fits beautifully into the modified brass
cradle be altered. Place some thin double sided tape on the back of the decoder & a piece of black
tape over the LED in the decoder – or it will shine red under the boiler instead of the firebox!
Note how the wires have been run. The Gray & Orange run behind the motor & solder onto the
motor terminals. The other wires run to the new PCB terminal strip.
You do have the correct soldering iron don’t you? The one that can be controlled to give a tiny little
bit of heat without burning the decoder wires? Don’t attempt this sort of work unless you really
have the right gear. If you plan on doing lots of decoder fits & sound go out & get an early
Christmas present for your wife now – a variable temperature unit with small medium and a bit
bigger tips – the small I use is 0.075” diameter with a point tip. She can buy you something else.
Fig.10 shows where the BROWN decoder wire was soldered to the G.M.E. sound cam that came
with the new loco. Solder it so it is flat & doesn’t keep the decoder body sitting too high.
FIG.11 Testing our work - wheels spinning
The photo in FIG.11 shows the loco (without the tender) running on the DCC track. The white LED
is a test to see my wiring was correct & when I pressed F0 to turn the lights on – it works.
I place a pin in the track to keep it in the one place hence the spinning driver wheels.
Notice I removed the pilot truck wheel set for safety while it’s being handled.
I wrapped tape around the wires just above the gearbox.
Now what about the next test… glass full is it? Mine is, I’ve needed a steady hand all thru this lot!
FIG. 12 (still spinin’)
The markers work, the headlights on & so is the cab light, & we soldered the speaker on to check
for sounds. Yep, bell rings, long whistle sings, short whistle too, ahh steam exhaust…..
(wait a moment I’ve just got to duck-out to the dunny to pump the bilge)……
Back now, Yep all the sounds work & the lights too – well, we’re a pair of geniusiz for
accomplishing a feat like this, let me buy you a drink my friend.
Well, most of the work has been done & all we need to do is put it all back together & get another
This expands on my little previous article on fitting SML’s into a K-27.
Until PART 2, remember to bring your own drinks next time - I’m just about out.
We will do the tender thing & fit the speaker in PART 2.
A big thank you to my excellent friends J.C. Zuloaga & Gerry Hopkins MMR
Your friend down-under,