Decoder wire cutting guide

Here is a trick I started using years ago to make my installations more quickly and more consistent.

With wired decoders, it's somewhat critical to get the length of the wires cut to just the right length.  Once you know the lengths, you could write them down for future installations in the same type of locomotive.  What I do to save time is to make a card like the one shown in the photo.  Then I just lay the decoder wires out on the card and cut each wire to the length specified on the card with a hobby knife.

It's also a good place to make notes on the card about this particular engine or installation.  For example, on this card I have noted that the white magnet on the motor goes to the top and that this card is referring to the use of an Aztec Trackmaster TM3008 frame and a Digitrax DZ125 decoder. 

Train Control Systems CN or CN-GP ?

The Train Control Systems CN type decoder is a good choice for some locomotives where they can be installed with little or no modification to the frame.  So what's the difference between the two and where can each be used.  I've been working with these quite a bit lately and have some answers.

The only difference between the two decoders is the shape and size.  The CN is shaped to fit between the parts of the frame that stick up on both ends of the Chinese made Atlas RS and RSD series of locomotives and is slightly longer than the CN-GP.  Refer to the photo above to see a comparison of both types. 

As the name suggest, the CN-GP is designed for the Chinese made Atlas GP series.    Both of these decoders can be used in other locomotives as well, sometimes requiring a little more modification to the frame.  The table below lists all of the locomotive types that I've installed these type of decoders in so far along with brief notes about the installation.  If I have related material in this blog, there will be a link to it.  This table will be updated whenever I discover another locomotive that the CN or CN-GP decoders can be used in.

 

Make and Model	Decoder type	Notes
Atlas GP7 and GP9	CN-GP	1995-1997 releases - see instructions
Atlas SD7 and SD9	CN-GP	Old release made by Kato - see instructions
Atlas Classic RS1	CN only	Reverse board locations - see instructions
Atlas Classic RS3	CN only	See detailed instructions
Atlas Classic RSD4/5	CN only	See detailed instructions
Kato SD40 or SD45	CN or CN-GP	Requires slot on top of frame for wires
Kato U30C or C30-7	CN or CN-GP	Requires slot on top of frame for wires
Life Like C424	CN-GP	Requires slot on top of frame for wires and reverse board locations, see instructions
Life Like GP60	CN-GP	Minor frame modification, see instructions

TCS CN in an Atlas Classic RS1

For the Atlas Classic RS1 I like to use the TCS CN decoder without removing any weight from the already light frame.  As many of the steps here are the same as with the Atlas Classic RS3, I will only focus on what is different from that installation.

Normally the part of the CN type decoder with the most components goes on the end of the frame that is the forward, or short hood end.  With the Atlas Classic RS1 this would require removal of some material from the frame however the decoder boards will fit perfectly if their positions are reversed.

The photo at left shows a top view of the standard layout to help understand how the decoder defines forward and reverse.  When we swap the position of these boards it's like reversing the red and black wires of a wired decoder.

Follow all of the steps in the RS3 installation except that the main decoder board will be at the long hood end.

Connect the orange and gray motor wires as shown in this photo which will be reversed from what they normally are.

At this point when you test run this engine, it should run backwards on DCC but in the correct direction on DC. 

To correct the DCC direction program the decoder for long hood forward.  This is done by entering 07 at CV 29 for 2 digit addressing or 27 at CV 29 for 4 digit addressing.

This photo shows an overhead view with the decoder boards installed.  After programming CV29 to compensate for the main decoder board being on the long hood end, the engine should run in the correct direction in both DC and DCC modes.

If you are modeling one of the railroads that considered the long hood of the engine to be the forward end, then skip the reversal of the motor leads and the reprogramming of CV29.

TCS M1 in a Walthers GP38-2

This how to episode first appeared on my old web site in December 2008.

The Walthers GP38-2 did not come with any provision to install a board type decoder but has room for one of todays small wired decoders.  Follow along as I install a Train Control Systems M1 decoder in this one.

As shown in the photo on the left the design of the engine leave space in key areas that we can use.  The existing PC board will be modifiyed and re-used.

Start by fully disassembling the locomotive and make a mark on the top of the motor.

Strip the PC board of all it's parts.  Then make the modifications shown in the photo on the left.  Save teh two resistors from the locations R3 and R4 that are marked "561" and re-install them at locations R1 and R2.

The LEDs that come with the Walthers GP38-2 are standard yellow ones.  I am going to upgrade to sunny bright white LEDs.  I remove the stock LED's from the board and use them as a guide to bend the leads of the new ones to the correct length.

Next prepare the decoder.  Cut the blue wire to a length of 3/4 inch.  Strip about 1/8 inch insulation from the end and from one end of the piece of blue wire that was cut off.  Twist the two stripped wire ends together and tin.

Now solder the two twisted together and tinned blue wires to the spot shown in this photo. Then route all the remaining wire ends through the hole to the top side of the PC board.

Next Solder the black and red wires to the locations shown in this photo. 

Next trim the yellow, blue and white wires to a length to reach the spots shown in this photo.  Strip and tin the ends and solder the wire ends to those locations. 

Cut the orange wire to a length of 1-1/4 inch from where it comes through the hole in the PC board and cut the gray wire to a length of 2 inches.  Strip and tin the ends and solder to the brush caps after they are removed from the motor.

Re-install the brushes, springs, and brush caps in the motor. The gray wire goes to the bottom and the orange wire goes to the top of the motor. Use a small amount of Walthers Goo to secure the gray wire into the groove filed into the motor housing in the previous step. Then wrap Kapton tape all the way around the motor where the brush caps are to insulate them from the frame.   Now reassemble the motor and worm gear assemblies into the right side frame as shown. With this type of mechanism that uses the rings to support the motor great care must be taken to insure that the rings are properly seated into the frame.

With the frame still laying on it's right side, place the washers that separate the frames into the holes and re-install the left frame. Make sure that the mounting rights are seated properly into both frames then re-install the screws and nuts.

Get the front PC board contacts started first, then being careful not to pinch the orange and gray motor wires guide the back of the board down onto the frame. Then push forward to fully seat the boards contacts into the frame.  When the board is fully seated into the frame it should look like the photo above. Lay the motor wires down over the board in the area above the motor. If necessary, secure them with some scotch tape.

TCS CN in an Atlas Classic RS3

This how to page first appeared on my old web site in July of 2008.  The CN type decoders were new then but have grown in popularity as they can be used in many engines.

Refer to the photo on the left.

This type of decoder uses two PC boards which take the place of the stock LED boards.  As the front board does no have a connection to the left half of the frame, both boards are needed for the decoder to work.  I really like the design of these decoders with the tiny but bright LED and large solder pads for the wires that make re-attachment possible.
For this installation I did not have to do anything to the frame.  I started by disassembling the engine and mark the top of the motor.   Lay the front board of the decoder out as shown in the photo on the left and cut the orange and gray wires to the lengths indicated in the photo.

Refer to the photo on the left.

Remove the brush caps from the motor, then remove the contact tabs from the brush caps.  Solder the wires to the brush caps.  File a slot on the left side of the decoder deep enough for a wire to fit but not all the way through the plastic motor housing.  Re-install the brush caps, spring, and brush.  The orange wire should lay in the slot as shown.

Wrap Kapton tape around motor as shown in photo on the left.  Place motor, worm gears, and bushings into the left side of the frame.  Take care to get the motor mounts seated correctly in the frame.

Assemble the frame again taking care to have the motor mounts properly seated.  Check that the flywheels turn freely.  Plug in the decoder boards and trim the black, blue, and yellow wires to a length that will reach the rear board then solder those to the pads indicated in the decoder instructions.

With this engine the way the shell sits on the on the frame leaves just enough space for the wires.  The wires must lay flat on the top of the frame and must not overlap.  Re-install the trucks and fuel tank.

At this point we are ready for a test run.

When satisfied with the test run without the shell, the shell can then be installed.  If the shell is properly seated on the frame, the bottom of the walkways should make full contact with the 4 tabs that stick out on the sides of the frame. 

In the photo on the left the trucks have been removed to make this more visible.

DONE !

First Post - That one in a thousand

A friend in Chicago who does his own installations called to tell me about a problem he was having with an engine that he had installed a decoder in several years ago and now was not working.  He had tried everything he knew how to do but was stuck.

So I had him send me his Kato U30C with a Digitrax DZ123 decoder.  When I got it I took the shell off and did a quick inspection of the installation.

• He had used an Aztec Trackmaster milled frame - OK
• The all of the wires appeared to have their insulation intact and not pinched anywhere - OK
• The motor turned freely when spun by the flywheels - OK
• The decoder was attached to the frame with a piece of double stick tape - OK

I then put it on the test track and sure enough, it would not respond to either DCC or DC.  I reset this decoder by programming 08 into CV 08. Then I got it to move on the default address of 03 but the LEDs were acting strange.  The rear LED was acting like a strobe when the engine was in reverse and the front LED was on all of the time.  I also noticed that this engine seemed to need a higher throttle setting than normal and I knew that the momentum settings were zeroed because I had reset the decoder.

Then I saw the smoke !



I immediately removed the loco mechanism from the track and removed the decoder from the double stick tape that secured it to the frame.  There was a burned spot on the bottom of the decoder.

As I had seen decoders burn out before, I thought that what it was a went about replacing the decoder.

In the course of doing this I had the mechanism completely apart and then back together again so I felt sure that everything was right.  This time before I put the wheels back on, I held the mechanism in my hand and placed each side of the frame on a rail.  I turned the throttle up and everything seemed OK, the motor ran and the LEDs responded as they should.  It was then that I noticed that the decoder was warmer than it should be.
 
I then decided to take a current reading on this motor.   I did this by placing my amp meter in series between the motor and a DC power pack.  I was surprised to see that this engine was drawing at least 400ma and up to over 1 amp when the throttle was advanced to near full.  Normal for an N scale Kato engine is between 200 and 300 milliamps. 



This ended up being a defective motor which over time, ruined the decoder.  As it turns freely, there must have been something wrong with the rotor windings.  This is not something that can be repaired and the motor must be replaced.  It must be really rare, that this happens as I have worked on many engines over the years and this is the first time I have seen this.  Replacement motors for Kato engines are generally available if you look around.  The motors are the same for almost all of the Kato engines but you may have to change the flywheels.