Inc Sound Module Decoder - Manual

www.digitrax.com- 11 -

are designated as N or Z sized decoders. That means that our N & Z decoders

are suitable for use in HO locomotives where space is tight.

For N & Z scale locomotives most modern high efficiency can motors draw

less than 1/2 amp when running and less than 1 amp when stalled at 12V DC.

However, we have found that many high performance N-scale locos actually

draw more than this and are comparable to HO locos. To ensure long-term reli-

ability, all current production Digitrax decoders are rated at 1 amp or more.

For large scale locomotives, it is particularly important to test the specific

loco you will use to determine the appropriate decoder to use. In many cases

for O, S, O-27 & G scale Digitrax 3, 4, or 5 amp decoders will the best choice.

If your installation has 2 or more motors, you will need to consider the stall

currents for both motors to determine the best decoder to use. In large scale,

there are often variations in the way locomotives are built so, it is important to

assess each individual locomotive before proceeding with decoder installation.

How to Determine The Stall Current Of A Locomotive

1. Place the loco (without the shell) on a track powered with regular

DC at 12V for HO & N Scales (Use 16V for G Scale).

2. Attach a DC current meter (ammeter) in series with one of the

track feeds. A power pack with an ammeter is good for this test.

3. Apply DC power to the track (12V for HO/N, 16V for larger

scales).

4. Stop the motor from rotating by holding the fly wheel or drive

shafts for a couple of seconds and measure the current that the

unit is drawing from the power pack while the motor is stalled.

5. Be sure that the power pack voltage remains at 12V (16V for G

Scale) during this test to be sure you get an accurate stall cur-

rent measurement.

6. Choose a decoder with at least the current rating determined with

this test. Digitrax recommends using the decoder with the high-

est current rating that will fit in your locomotive for long term

reliability.

3.3.3 Which Decoder Will Fit?

The space available inside the locomotive is a major factor in choosing which

decoder to use for your installation. Many sizes & form factors are available.

Visit www.digitrax.com/decoderselector to see our recommendations for many

locomotives. Complete information, including size measurements, for each

decoder is available in the product section of the website. Instruction Sheets