General Decoder Installation Instructions

(Note: for specific installations go to this site (click here)

 

Before you start.

If you have an analog ohm meter, you must “zero” the meter each time you use it and after you change ranges. This is done simply by shorting the probes together and rotating the adjustment dial until the meter reads zero. Note that the ohms scale starts on the right side of the meter.

You don’t have to zero a digital meter. However, you will find that a digital meter never reads zero. Typically it will read 0.4 to 0.6 ohms. This is normal. There is nothing wrong with the meter.

These are general decoder installation instructions intended for older locomotives that have no electronic components inside of them or somewhat newer locomotives that may have a few electronic components in them, but do not have an 8-pin connector in them for a DCC decoder and probably were not intended to be DCC ready or were made prior to DCC.

There are three phases to installing a decoder in a locomotive.

I. Figure out how the locomotive was wired.
II. Disconnect everything in the locomotive.
III. Wire in the decoder.

 

 

I. Figuring out the locomotive’s existing wiring.

Locomotives that have no electronic components are all wired the same way. The headlight is wired in parallel with the motor. One side of this parallel combination will probably be connected to the chassis if it is metal. This in turn will be connected to some wheels for power pick-up.

You can confirm this by using your ohm meter. Touch all your wheels, including the tender wheels with one probe of your ohm meter. Attach the other meter lead to one of the leads on your motor. If you do all the wheels without moving the test probe on the motor, you should get two sets of readings. One set of readings will be from the motor lead directly to the wheels. The other set of readings will include the resistance of the lamp and motor. Don’t panic if you can’t tell the readings apart at this stage. If you figure out which wheels you are getting power from, you are doing fine. Note that some locomotives may be using tender wheels, in addition to or instead of, driver wheels to pick up power.

Disconnect at one wire going to the motor. Check with yourhm meter and determine if that wire is going to the “engineer’s side” (right side with loco facing forward) or “fireman’s side” (left side with loco facing forward). Note this for later. If you will have to take the motor out and may rotate it, put a mark on the motor so that you know which terminal the removed wire went to.

II. Disconnect everything in the locomotive.

If the locomotive has any kind of electronics in it (but was not purchased “DCC ready”), you will be removing them. This includes directional lighting, constant lighting, mars lighting, and electrical noise filtering circuits.

If the headlight is connected to the chassis, remove headlight and replace with a grain of wheat bulb (for HO) or a grain of rice bulb (for N) in series with a 680 ohm resistor (Radio Shack p/n 271-1117). Do not connect any headlight wires at this time.

Disconnect both wires going to motor. If only one wire is going to the motor, than the motor is connected the chassis. Even if you have two wires going to the motor, after disconnecting the wires, use your ohm meter to ensure neither motor terminal is tied to the chassis. Check and see if the chassis also connected to wheel pick-ups. You must isolate the motor from the chassis! Use your ohm meter to ensure that the motor is isolated when you are done. This is important! If you don’t do this, you will likely “let the smoke out” of your decoder. Once you let the smoke out, electronic devices never work again.

With the headlight and motor disconnected, you should now be able to use your ohmmeter to conclusively determine which wheels your locomotive is using for electrical pick-up.

III Installing the decoder.

1. Connect the red decoder wire to the “engineer’s side” (right side with loco facing forward) wheel pick-ups.

2. Connect the black decoder wire to the “fireman’s side” (left side with loco facing forward) wheel pick-ups.

3. Temporarily connect the orange decoder wire to one of the motor leads. If you noted which of the wires that were going to the motor were from the engineer’s side, attach the orange wire to the motor lead that you previously identified as the engineer’s side.

4. Temporarily connect the gray decoder wire to the other motor lead.

5. Very important! Test your locomotive on address #03. It should move smoothly and in the direction set on your throttle. If it does, you can permanently attach the gray and orange wires. If the locomotive goes in the wrong direction, reverse the orange and gray wires before permanently attaching them.

6. Connect the white decoder wire to one wire of your headlight (or to the resistor if you are using a grain of rice bulb).

7. Temporarily connect the blue decoder wire to the other wire of your headlight.

8. Very important! Test your locomotive. Function 0, with the locomotive commanded to go forward, should light the headlight.

9. Connect the yellow decoder wire to your rear headlight. Or connect the yellow wire to a resistor if you are using a grain of rice bulb.

10. Temporarily connect the blue decoder to the rear headlight.

11. Very important! Test your locomotive. Function 0, with the locomotive commanded to go in reverse, should light the rear light.

12. Your decoder may have other wires that control functions. Hook them up to your mars light or whatever as if they were a headlight. Be sure to install a 22 ohm resistor in series with any light to be used as a mars light, flashing, pulsating, or gyrating light. If you are using a grain of rice bulb and a 680 ohm resistor, you do not need to add the 22 ohm resistor.

13. Make all your temporary connections permanent and you are done.