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My MMI Hon3 K-27 Locomotive came with a 12v DC globe for the headlight and a 12v globe in the cab. It came DC ready but I needed to convert it for DCC, add decoder, sounds and speaker. But first to get the lights I wanted!
I removed all the original wires and 12v globes & the circuit board that came for DC as it was taking up too much space in the loco. I planned to fit a Soundtraxx Micro Tsunami #750 in the loco body and a speaker in the tender.
I worked using a 6 inch magnifying glass with inbuilt light so I could see what I was doing with such tiny pieces. I also use an adjustable heat soldering iron with a very small pointed tip. This is a MUST for doing DCC wiring, to get low heat and NOT burn things!
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The existing holes where the front and cab light wires ran were used for the new Surface Mount Device (SMD) Light Emitting Diodes (LEDs). These being white light & 0.8mm diameter with 5 inches of enamel wires attached. The enamel being the insulation covering.
Firstly, I placed one of the LEDs into the headlight and centered it to see how it fitted and looked - looked good. I then super-glued (ACC) a 1.5mm square of thin cardboard to the back of the SMD LED so the terminals would be protected from contacting the loco body through the metal detail casting of the headlight. I then placed more ACC on the back of the cardboard & glued it in the centre on the back of the headlight. This was then tested again to ensure the light worked & the beam looked correct - it was.
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Secondly, I prepared both the Classification Marker lights either side of the headlight. To do this I used my Exacto-knife to clean away any paint "lumps" & high spots in the back holes of each marker. Then I "test-fitted" each of the SMD LEDs into the back hole of the markers.
NOTE: The back hole on the marker casting is slightly rectangular and so is the SMD shape so it makes for a nice snug fit and the LED actually goes in a little so that the lens fits perfectly (A nice casting from PSC MMI).
With both LEDs tested, and the fit confirmed, a good close and tight one, I removed the LEDs and placed a TINY drop of ACC onto each SIDE of the SMD. Placing such a small amount on each side prevented any ACC getting onto the lens and it was just enough so that if needed to, it could be removed later. I let the ACC dry overnight.
The tiny wires from each marker were run to the headlight bracket & tucked down behind it so they were not visible. They were painted with acrylic carbon black to hide the "copper" colour of the wires.
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THE RUNNING OF THE WIRES |
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The wire "pairs" from the 2 marker lights and the headlight (total of 6 wires) were twisted together & fed through the existing hole at the top of the smoke box. They are hard to see once painted black. The ends of the enamel wires I found difficult to "tin" even though I scrapped off the enamel coating. They are finer than a hair!
Anyway, I cut two pieces of PCB from a Clover House strip (used for hand laying track) to use as a terminal for the wires. I tinned the PCB and made a small "puddle" of solder so that the tiny wire ends would sit in the puddle. This worked fine & I connected the decoder wires to the PCB terminal pieces. The PCB was ACC to the boiler and insulation heat shrink covered the bare wires.
NOTE: All Decoder wires MUST have insulation of some sort placed on them! If a wire was to touch or something comes adrift, it could cause a short of blow-up the expensive decoder!
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Tip From
Richmond Controls |
Stripping and tinning the enameled LED wires is the easiest thing you can do if you use the right technique. That wire is called "solderable" by its manufacturer, which means that the enamel degrades and comes off then the wire is plunged into hot solder. Generally this has to be done once and then repeated, because the first attempt generally leaves a glob of charred varnish on the soldering iron tip. The technique is to separate the wires, accumulate a healthy blob of molten solder on the soldering iron tip, apply liquid flux to the wire, and plunge the wire into the molten solder blob. It typically requires more than one attempt to achieve a clean and attractive end result.
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THE CABIN LIGHT |
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I again used a SMD 0.8mm white LED for the cab light. The original 12v globe didn't light up the cab that much so that the back-head detail could be seen properly.
I ACC in placed a tiny square of thin cardboard onto the back of the LED so it covered the wires and LED "pads". Then I ACC the cardboard & LED to the roof of the cabin slightly aiming the light down and onto the back-head detail which showed the white gauges & red handles of the various valves etc. This gave an intense light that really brought the cab to life yet was not overdone in any way. I was very pleased with this result.
The wires were then run back into the boiler via the existing hole and joined onto the same PCB terminal as the front 3 lights. A single 1k resistor is used and the 4 SMD LEDs are wired in series so that the current rating of the decoder is not exceeded. This is where a costly mistake can be made and keeping below 100 ma per the manufacturer's specifications MUST be done.
My #464 came with no reversing light (per era modeled) however I will be fitting a reversing light and using a 3mm Yelo-glow LED.
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Tip From
Richmond Controls |
Avoid using ACC (superglue) when working with LEDs, because it tends to be so permanent. A wonderful option is Pacer's Formula 560 Canopy Glue, generally found in model airplane shops. It gets firm but never hard, it lets go with a bit of persuasion, and is clear when cured. It is also recommended that Pactra BLACK Racing Finish (also found in model airplane and RC shops) is used for painting the Canopy Glue if you need to block the light coming out the back. The Canopy Glue is also both a sealer and an insulator (for covering bare wires) -- in fact, the Racing Finish also works as a flexible insulator.
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For operation, the 4 LEDs fitted on the loco will come on with the dynamo sound for moving forward. For moving in reverse, only the rear / tender light will be on. The loco engineer turns off the cab light in reverse so it doesn't distract him (that's my story anyway). The headlight when lit, shows the bulb / filament which makes for a nice looking and realistic light.
The photos show some of the steps and the end result. I hope this will help you in trying to fit Classification or marker lights, headlights etc. |
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Tip From
Richmond Controls |
It is recommended that the wires on those LEDs should never be cut unless absolutely necessary. Instead, grasp the midpoint of the twisted wires with sharp pointed tweezers and twist to form a tight coil. This takes up as much slack as necessary. The coil does not uncoil when you remove it from the tweezers' tips. |
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It's been a real new experience doing this refit on the MMI K27 & I would like to thank Gerry Hopkins (MMR), Jim Vail (MMR) and "JC" Zuloaga (California) for their help and information regarding the Micro Tsunami fitting, it is truly appreciated. For them to share their knowledge so that others can become better modelers allows everyone in the hobby to embrace such friendship & the sharing in our hobby. In fitting the SMD LEDs into my loco marker lights it is yet another step forward with new technology and it gave me much pleasure. |
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