Kit: MX648; SugarCube8; SMD Nano firebox LED
The Hornby OO M7, with DCC sound using a Zimo MX648 and firebox glow. The M7 is a pretty thing, but very short on space for
treats! So we've got to do away with the DCC socket, to make room for the decoder or speaker. In fact, there isn't going to be
enough room to get both the decoder (Zimo MX648) and speaker in the boiler, so we decide to put the decoder in the bunker.
Off with all the gubbins, socket, supression capacitor etc.
Grind the socket's screw mounts flat:
A SugarCube8 goes under the chimney, just about. It could sit upright like this, with some electrical tape between it and the
...but in fact, we choose to place the speaker the other way up, and stick it under the chimney like below. Just measuring the
space at the moment, and refitting the body to ensure that it will be able to go back on flush when we're all done:
We're happy with the fit, so we add speaker wires, and stick the speaker into its' final position using a thick double-sided
Since we don't have much room, we will totally remove the unwanted wires from the decoder (white, yellow and brown in this
case). I have also replaced the orange, grey, red and black wires with much longer ones, as we need to run these up to the
motor and pickups. We keep the green and blue though, as we want to add a firebox glow light... before and after wire removal
(DO NOT do this unless you have good soldering skills and a decent fine-tipped soldering iron!!):
Cut out holes under the bunker floor for the decoder wires to go through - it is actually easier to remove the coal from the
bunker and feed down from the top - you don't need holes as large as what I've made here! I've also routed trenches for the
motor, pickup and speaker wires to sit in as they go forward, including a channel vertically up behind the smoke box - this
will prevent the wires from getting pinched when we put the body back on later.
The firebox glow light is an orange SMD LED, glued onto the smoke box door. We can get away with this simple approach on a Tank
engine, because the LED is not directly visible. Paint the white parts of the LED, and the wires black to help disguise them
though, and feed the LED's wires through the floor, routing back to the bunker.
The firebox LED needs a resistor on the positive wire, before attaching to the decoder's blue wire. The LED's negative wire
attaches to the decoder's green function wire. We've used heat-shrink to totally cover the resistor and electrical joins.
Stuff it all into the bunker, and chop the pivot legs from the coal moulding, as the coal will have to sit slightly higher than
it previously did. In fact, once in, we'll glue on some lump coal to improve the look!
All in, tested, firebox glow on - beautiful!
Kit: MX648; IceCube18X13X10-1W; LifeLink with SuperCap17000uF; SMD Nano firebox LED
Remove the 8pin DCC socket and flatten the platform under the chimney.
Test-fit the SuperCap 17000uF in the side tank, which looks to be a perfect fit.
Screw mounts from the DCC socket are milled down flat.
From the top of the bunker, remove all the plastic, leaving suppport for the retaining screw at the base. This is where our
large IceCube speaker will go.
Purple speaker wires added.
MX648 has been rewired, removing unwanted lighting wires (white, yellow and brown), and adding GROUND wire for the stay-alive,
then re-cover in Kapton tape.
Nano SMD firebox glow LED is glued into position in a hole made into the cab, and the wires channelled and protected with some
LifeLink PCB sits on top of the decoder.
YouChoos 3D Printed crew figures added, and weathering applied - lovely!