Need help

[depmuht]

I am looking for a wiring diagram for putting a Bachmann 44913 into a Bachmann EMD GP40 Diesel. Can anyone help me? Thank you.

[Jim Banner]

Wiring a decoder into a Bachmann diesel is quite straight forward:
RED decoder wire to the wheel pickups on the right side of the locomotive.
BLACK decoder wire to the wheel pickups on the left side of the locomotive.
ORANGE decoder wire to the motor terminal that was formerly connected to the right side wheels.
GREY decoder wire to the motor terminal that was formerly connected to the left side wheels.
WHITE plus BLUE wires to the headlight.
YELLOW plus BLUE wires to the rear light, if any.

I am assuming you know the rest, but will repeat them here for others reading your post:
BEFORE installing the decoder, you must:
- Disconnect all wiring from both motor terminals and be sure they are isolated from the chassis.  Power is often carried to one or both motor terminals through the frame or frame halves.  Use an ohmmeter from one motor tab to the frame, to the wheels and to the lights to be absolutely sure the motor has no extraneous connections.  Failure to remove all connections (except to the decoder) can and will destroy the decoder.
- The lighting outputs of decoders put out about 12 to 14 volts.  If your locomotive has 12 volt light bulbs, you can connected them to the decoder with a resistor of about 22 ohms in series with one lead.  Or you can install LED's using a 1000 ohm resistor in series with one lead of each LED.  Most LED's have one long and one short lead - the long lead connects to the BLUE decoder wire.  If you are using LED's front and back, both long leads connect to the same BLUE decoder wire.  Be absolutely sure that the light bulbs or LED's have no other connections such as to the frame or any of the wheels.  Many locomotives have lighting boards to control the lights when running on dc.  My personal practice is to remove these boards and wire LED's directly to the decoder (with, of course, the 1000 ohm resistors.)  I find it quicker and easier to make the few extra connections than to follow the traces on the board.
- Solder all wire joints and insulate them with shrink tubing.  Do not give in to the temptation to use tape.  Tape will fail in the hot environment inside your locomotive, leaving you with a sticky mess to clean up if you ever want or have to make changes.

Jim 

[depmuht]

Thank you for your help. This is my first time doing this so it was helpful. I dont have any resistor to put between the decoder and the lights so can I use the resistors in the board between the decoder and the light? Thank you again for your help.

[jward]

resistors are available at modest cost at any radio shack.

that said, you can determine the value of the resistors on the light board and buy the appropriate value to replace them if you know the colour code on the resistor itself...resistors have 3 or 4 bands on them, of different colours. the first 3 bands identify the resistor's value in ohms. the code is as follows:

black = 0
brown = 1
red = 2
orange = 3
yellow = 4
green = 5
blue = 6
purple = 7
grey = 8
white -9

to read the code, the first two bands are the numbers listed after the colour. the third band indicates the number of zeroes added to the value of the first two numbers....

example, 22 ohm resistor- red-red-black (2-2-no zeroes)
1000 ohm resistor-brown black red (1-0-2 zeroes or 1-0-00)

reading this code will keep you from guessing what value of resistor to use to replace the light board.

[depmuht]

Does it matter which lead i use off the bulb?

[Jim Banner]

To add to Jefferey's post, the first band is the band closest to the end of the resistor.  The fourth/last band is either missing (there is a space) or is silver or is gold.  Resistors are manufactured only in certain values as below:

10, 15, 22, 33, 47, 68, 100  ohms (resistors with no fourth band - the value is accurate +/- 20%)

10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 81, 100 ohms (resistors with silver fourth band, the value is accurate +/- 10%)

10, 11, 13, 14, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91, 100 ohms  (resistors with gold fourth band, the value is accurate +/- 5%)

All the above values are available multiplies by .1, 1, 10, 100, 1000, 10,000,  and 100.000

Don't worry about the accuracy ratings - most resistors used today are 5% or better anyway.  Do worry if a resistor you read a value from does not fit into the above table.  Try reading it the other way round.  If it still does not work, it is probably not a resistor.  One exception is a zero ohm resistor, marked with three black bands or sometimes with a single, wide black band or sometimes not marked at all.  These are "step overs," basically pieces of wire that automatic insertion machinery designed for putting resistors into boards can easily handle.  They allow one printed circuit board trace to cross over another without having to use much more expensive double sided boards.

Having said all that, the board in your locomotive may not contain any conventional resistors.  The manufacturer may have use Surface Mount Technology components.  SMT resistors look more like little squares of Sen Sen than like electronic components, and usually have the values printed on them.  They are not very useful for putting in series with the wiring to lights.  With conventional resistors, it is easy to snip the wire, strip the ends, then cut off all but 1/4" of the resistor leads, and solder one wire end to each resistor lead.  The whole thing can be easily insulated with shrink tubing - use a size that just slips over the resistor.  To shrink the tubing, tickle it with the flame of a butane cigarette lighter, which is to say, do not hold the tubing steady over the lighter flame but wave the flame back and forth a bit to make sure you don't char the shrink tubing or worse, set it on fire.



It does not matter which bulb lead you use.  There is a law in electronics that says if you put components in series and hide them in a black box, there is no way to tell which comes first, second, etc. by measurements made outside the black box.  This is true when using dc and the low frequency ac we using in model railroads but sometimes breaks down at microwave frequencies and beyond.

Jim

[depmuht]

I have done some automotive electronics which kind of helps. It did look like it had the regular resistors in it( they are green colored piece with the colored bands). The bands look to be yellow purple and two silver. The other thing that is confusing me is that the wires that go to the motor. The red wire comes from the motor to the board and the spot is marked mo-, the black comes up to a spot marked mo+. All the thing I have worked on have been red positive black negative. This is not a positive ground system like the old thirties and forties car is it?

[depmuht]

The other thing I wanted to check is it has a red wire coming out of the trucks on one side and a black out of the other. If you were sitting in the engine facing forward the red would be out of the left side and the black out of the right side. I apologize if I am asking to many questions. I just don't want to screw it up and ruin anything. So THANK YOU for your patience and help. 

[jward]

positive and negative in a dc locomotive are confusing terms. in order to reverse direction, the polarity must change, thus positive becomes negative and vice versa.

the convention in dc locomotives is that the right hand rail is always positive no matter which direction the locomotive is travelling. is you switch the positive to the other rail, the locomotive reverses direction.

with dcc it is not really important whether you get these two leads reversed, as long as the ONLY electrical path to the motor goes through the decoder. mix up the red and black leads, or the grey and orange leads and the locomotive will run backwards. you can easily correct this by reprogramming cv29 in the decoder.

on a related note, that direction adjustment in cv29 comes in handy if you model railroads like the b&o, pennsy, and several others whose early diesels like the gp7, gp9 and rs3 ran with the long hood as the front.

to answer your question about the truck wires, ignore the wire colour. connect ONLY the left side wires together, and ONLY the right side together. cross them and you have a dead short.

[depmuht]

I figure I had to keep left and right separate, I just was not sure if the Pos and Neg mattered. But you are meaning left and right as if you were sitting in the cab correct? Can I use the resistor from the board for the lights? The thing I am wondering from looking at the board it look is like the bulbs do not have a resistor between the pickups and the bulbs. The pickup wire from the wheels are soldered to the board right next to the point were the bulb is soldered to the board. It looks like the resistor is between the motor and the pickups. Thank you agian.

David

[Jim Banner]

No, I don't think it is "positive ground" much loved in British cars as either or neither motor terminal could be connected to the locomotive's frame.  More likely it is the Chinese version of colour coding, also known as "anything goes."  Easiest way to figure it out is to disconnect the wires from the board and hold them onto the terminals of a 9 volt battery.  If the locomotive moves forward, the wire connected to the battery's + terminal is the one that connects to the motor's + terminal where the decoder's orange wire should go.  If the locomotive moves backward, the battery's + terminal is connected to the motor's - terminal where the decoder's grey wire should go.

Yellow, violet, silver, silver?  The first silver is a multiplier = x .01 (gold band as a multiplier = x .1)  So your resistor is .47 ohms.

Jim

[depmuht]

So with the way it is on the board I do not need a resistor between the bulb and pick up then, and the decoder goes between the pick ups and the motor then.

[depmuht]

Many thanks to Jim and Jward for all the help. Everything went good. Thanks agian for your help.