Page 24 - May June 2020

Basic DCC Decoder Installation
Part 1: Getting Ready Mick Moignard
INSTALLING DCC
T hese days nearly all loco- motives are “DCC ready”,
however, there will be a time
when you need to install a decoder into a model that is just plain
DC; no decoder and no provision for a socket to plug it in. I can’t give you a to- tally definitive installation guide because each locomotive is different, but what I can do is take you through the steps and give you some hints.
First thing is tools. You’ll need screw- drivers, tweezers, pliers, the kinds of thing found in most toolboxes and a soldering iron, somewhere between 20 and 50 watts is ideal, with a fairly small tip that can be pointed, chisel or ellip- tical, but the key is small, no more than 2mm in diameter at the tip plus you will need electrical solder, the rosin cored stuff. These days we’re encouraged to use lead-free solder, but personally I still use lead-tin solder, mainly because it just works better, particularly for electrical work. It’s also worth having a small sup- ply of decoder wire, 28AWG or smaller, which is easy to find on eBay, and some 1.2 or 1.6mm heat-shrink tubing to go with it. If you’re also going to be fitting lights, some LEDs will come handy, with appropriate resistors.You’ll be able to do a lot of installs using regular 3mm cool white, also known as sunny white, LEDs. For the purposes of this quick guide, however, I’m not planning to cover adding lighting to a model that doesn’t already have it.
Lastly, a cheap multimeter is useful, as well as a small supply of Blu Tack.
First thing to do now is check that the loco you want to convert runs OK on DC. DCC will cure quite a lot of evils, but it won’t fix a poorly running loco, or a noisy one. If need be, perform a service on it, careful lubrication, particu-
larly the motor bearings as these are the fastest moving parts in the loco and clean the wheels and pickups, getting all the embedded fluff out.
Now that you have the body off, ob- serve the chassis and the body and look to where you might place the decoder so that you can choose an appropriate one. For these articles, I’m doing a plain non-sound install in an N-scale Key Imports Southern Pacific GS-4, so I’m going to need a small, wired decoder. I’ve chosen for this project a Digitrax DZ126 decoder, which is around £21. It’s a 1-amp wired decoder with two lighting outputs and will fit and operate just about any HO loco and is small enough to fit in pretty much any N scale loco too. Also useful, somewhat larger than the DZ126, is the Zimo MX600, which is around £20. Zimo motor control is about as good as it gets, but the MX600 is about twice the size of the DZ126 and is only a 700ma de- coder, so its best used in smaller locos. It would not fit in the GS-4 loco, but there is plenty of space in the tender for it. When choosing a decoder, you should also note that TCS, Digitrax and Soundtraxx all have Decoder Selectors on their websites, which will show you their recommendations for the most practical decoder for your loco, though it only covers RTR locos. TCS, Zimo, Soundtraxx and Digitrax decoders are all available from Ted Smale at SCC see their ad on page 25.
The amperage rating for the decoder
is important; if the loco motor and functions draw current more than the decoder can cope with, the decoder will almost certainly fail. Many decoders have some measure of overcurrent pro- tection and some even extend that from the motor outputs to the function out- puts, but not all do and anyway, it’s not
How to measure Stall Current
To do this, you need a supply of DC power of at least 1.5 or 2 amps, and a multimeter capable of measuring up to 2 amps. Most cheap digital meters are able to measure up to 10 amps and are just fine for this.
Place the loco, or even just the chassis on a piece of track and connect that to the DC supply.
Check that the loco works. Now remove one of the wires from the powerpack, connect it to one wire on the multimeter and connect the multimeter’s other wire back to the track, so that the multimeter
is in series with the loco. Set the multimeter to the high current setting. Restrain the loco and turn the DC controller up to full speed. Now press down on the loco to stop the motor moving, or, if you’ve got the body off, just grab the fly- wheel to stop the motor and while the motor is stopped, observe
the reading on the multimeter. I’d expect something between 0.5 and 1.5 amps.Whatever the reading is, the decoder needs to able to cope with it, with some headroom, which will also allow for the lights.
You can read a lot more about checking the stall current here: https://sites.google.com/site/mark- gurries/home/decoders/decod- er-motor-ratings
a good idea to run the decoder at or near its limits it will make it run hot and it will shorten its life. If you’re not sure, you can test the motor’s stall current
– see the sidebar above. You’re really
ROUNDHOUSE - May/June 2020
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