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Decoder Installation into an

Mountain 4-8-2

This installation note assumes you have read the section on Wiring Specific Locomotives.

This locomotive looks like it will be easy to wire in a DCC decoder.  It is.  Getting it back together, however, will be a little bit challenging as IHC filled the boiler with weight.  Don't you hate when that happens???

The headlight is mounted on the frame, rather than the boiler.  This fact, coupled with lead-filled boiler, means your headlight wires will have to run down the side of the boiler; tucked underneath, but visible.  Be sure to use small black wire.  Be carefull and you will have no trouble stripping the wires to the existing headlight.

The motor is already isolated from the power pick-up and frame in this locomotive.  Regrettably, only two of each of the driven wheels on each side provide power pick up.  Also, some of the tender wheels are used.  In no cases did I get a good, low resistance reading to any of the wheels.  Using conductalube on the back at the power pick of all the wheels' power pick up points is essential with this locomotive.  Also use Conductalube at the swivel points of the tender trucks.

R1 is 22 ohm, 5%, 1/4W resistors.

Use at least a 1A decoder with this locomotive.  A Digitrax DH140 was used for this installation.

On the locomotive, the connector is on the right side.  On the tender, it is on the left.  You will need all the decoder wire length (and then some on the headlights) so I milled out the tender on the right side.  Leave the decoder loose in the tender so the wires have minimal springiness else causing derailments on curves.

The can motor tightly occupies the firebox area.  I could only get two flickering firebox lamps in.  If you use grain of wheat bulbs, you could probably get four.  I'm happy with the two.  Before assembling the locomotive, drill several holes in the frame so the firebox lights shine down on the track.  Be sure you read and understand how the Digitrax keep alive and flash rate is set iforCV 62 in their manual.  Adjust these values to suit your taste.
CV Value Function
01 20 Set to short address 24.
29 02 Set decoder mode to short address.
49 68 Rule 17 Headlight F0f.
51 21 Flickering firebox F1.
62 24 Keep alive brightness (left digit 0-F).  Rate (right digit 0-F).

Though not required reading, you may want to read the section on Hexadecimal Demystified.

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