DZ121 in an Athearn F59PHI

This how to first appeared on my old web site in June of 2004.  Since that time the decoders mentioned have been replaced with newer models.  I would suggest the TCS M1 or Z2, or the Digitrax DZ125.  I don't think a board type decoder was ever made for this engine.

There is plenty of room for a small decoder without any modification to the frame. In this example I used
a Digitrax DZ121 but a DZ123, DZ143, or any similar sized decoder would also work.
The key to this installation is using the existing circuit board. The drawing of the board at the right shows all the steps taken to modify the board and then make all the connections to complete the installation.  Below are several photos to help clearly see what the installation should look like.

In this photo you can see where a section in the middle of the board has been removed for the decoder.  I used a Dermal tool with a cut off disk to do this.

After that the holes for the resistors get drilled & the circuit traces between the holes get cut. Then reverse the Led on the forward end of the board.

Next install a 270 ohm 1/4 watt resistor at each pair of holes. You will need to scrape away the green plating from around the holes before soldering.

An update to the way this was done in 2004 would be to change the yellow LED's to the bright white type of LED's. If this is done you may also want to change the 270 ohm resistors on the board to a higher value.

Note in the close-up to the left how the circuit trace has been cut between the points where the resistor is soldered.  This was also done with a Dermal tool and cut off disk.
 
These are the wire lengths that I use for this installation.

Black = 1-1/8"
Red = 1-1/16"
Orange = 15/16"
Gray = 1"
White = 1-3/8"
Yellow & Blue = 3/4"




Remove the motor brush mounts from the motor before soldering the orange and gray wires to them.

Then solder the white and yellow wires to the board at ends of the resistors that are away from the LED's as shown in the photo.

Cut the plastic bar that goes across the top of the wire channel on each side.  Reinstall the motor brush mounts with the orange wire going on the right side and the gray wire going on the left side.

Then solder the black wire to the tab on the bottom of the left side and the red wire to the tab on the right side.  Finish by tucking any excess wire length under the board and placing a piece of scotch tape over the decoder to hold it in place.

A most unusual shorted axle

Yesterday I had received an N scale Precision Craft E8A that I had installed a decoder in about 2 years before that now shorted the DCC system whenever it was put on the track.

The Precision Craft E8 is designed like a scaled down HO engine because it uses wires from the trucks, motor, and LED headlight that all plug into a circuit board.  The board also has an 8 pin connector that either has a decoder or jumper wires if it has no decoder.  I recalled that what I had done was to cut the jumpers on the original plug and then to solder the wires of a DZ125 decoder to the pins.

Here is a stock picture of a decoder like so you can get an idea of what this looks like.



This plug arrangement came in handy when troubleshooting this problem as I did not even have to turn on the soldering iron.  After first verifying that the locomotive indeed did cause a short of the DCC system as soon as it was on the track, I began to unplug things.

• Unplugged the decoder, still got a short.
• Unplugged the motor, still got a short.
• Unplugged the rear truck, still got a short.
• Unplugged the front truck, still got a short.

At this point, I placed each truck on the track one at a time and discovered that the front truck was the source of the short.  Because all three axles are picking up power and are connected on each side by a metal side frame I took the truck apart to test each axle and find the one that was shorted. 

First I checked the wheel gauge with an NMRA N scale standards gauge and it was OK.  Then pulling the wheels out from each side I could see that the pins that come off the wheels and insert into the plastic tube part were long enough for the ends to touch inside the plastic tube part.  I then took a bit off the end of one of the axle of one of the wheels  with a Dermal tool cutoff wheel and that solved this problem.

Almost all N scale locomotive axle assemblies look like the photo at left.  Two solid metal wheels with metal axle pins that insert into the ends of a plastic tube that has a gear.

It is easy to see how this could happen on any locomotive when the total length of the two metal axle pins are longer than the length of the plastic tube.

I would suspect that this could happen after someone pressed the wheels together to correct the wheel gauge.  The owner of this engine said it started after the engine had derailed.  I suspect that the ends of the 2 axle pins were already very close to touching and getting bumped by the derailment was just enough to make them short.  This ended up being one of those very unusual problems that I though was worth sharing.  I was relieved that the problem had nothing to do with my workmanship and the owner of the locomotive was relieved that the decoder was not burned out.

Building a decoder tester

I have always found it useful to have a "simulated locomotive" with an actual motor to test decoders.  Back when I started working with DCC, I threw something together from the junk box and ended up using that for many years.

In 2010 that one finally fell apart and I set out to make a nicer one and here it is.



Here's a peek inside.   To keep things simple I mounted all of the components on the top half of the two part plastic project box.  The size of the box is 5-1/2" x 3" x 1-1/2".





 
The cord that comes out of the box has a Cinch Jones connector on it that I can plug into these two receptacles on my layout control panel.  The layout uses a Digitrax Chief System.

I also have an old Digitrax Big Boy system mounted on a board that I use on the work bench and this decoder tester can also be plugged into that.



 
Here's a drawing and a parts list along with where I found them.

Besides marking the color for the binding posts, the banana plug sockets are for any special leads needed to connect to board type decoders.

1. The nickel plated binding posts are Grayhill 29-100 BLK which I purchase from Allied Electronics.  Their part number is 948-7392.  At $4.79 each, this was the most expensive part of the project.
2. E-Z Hook 9284-5R is a set of banana plug jacks that I found at Fry's Electronics for about $6.00.  The Fry's part number is 18206.  The full set had 10 jacks with colors matching the wires on a decoder.  I did not use the violet or brown ones but if you are working with HO scale decoders that would be something to consider.
3. Motor assembly from Kato E8 or PA locomotive.  I used this one because the mount was easy to attach to the inside of the box with Walthers Goo.  A striped pattern was printed on adhesive labels and attached to the flywheels to the motors rotation would be easy to view through the windows.
4. Three yellow LED's taken from Atlas locomotives when they were upgraded to bright white LED's.  One each for the white, yellow, and green (F1).

Digitrax DZ123 in a Life Like GP60

This how-to page first appeared on my old web site in December of 2004.

The Life Like GP60 is really a great model but did not come with a provision to install a DCC decoder. To get DCC into this model we will use the Aztec Mfg TM3031 Trackmaster frame and a Digitrax DZ123 decoder. A Train Control System M1 would also work very well in this application. Start by completely disassembling the engine and marking the top of the motor. I always recommend testing a new decoder before cutting any of the wires so do that

now if you have not already. Then cut the wires to the lengths listed below. 

 

2 - 1/8" - Red, Black, & White wires

1 - 3/4" - Gray wire

1 - 1/8" - Orange & Yellow wires

The diagram to the left shows the modifications to the rear PC board and where to connect the yellow wire.

The diagram below shows the modifications to the front PC board and where to connect the red, black, and white wires.

Remove the motor brushes from the motor and solder the orange and gray wires to the motor brush caps.  Next file a groove down the right side of the motor as shown in the photo on the left.  This will be for the gray wire.

This photo shows the front PC board after the engine is re-assembled.

This photo shows the rear PC board after the engine is re-assembled.

To get the gray wire down to the lower part of the motor use a needle file again to notch a groove into the side of the motor housing as shown in the photo. I did this on the right side of the motor but it could be done on either side. Be careful not to get any debris inside the motor.

After the mechanism is re-assembled this is what you will have. The DZ123 is a fit tight. fit.  The TCS M1 is a little narrower and the fit will be easy. The fact that the frame has an undercut that the decoder fits into makes it secure and you will not need any tape to hold it in place. This model has nice locking bumps on the frame like some of the Kato models to align the shell.

Digitrax DZ125 in a Kato F3/7B

The original Kato F3/7 mechanism requires frame modification to fit the decoder.  I always send mine to Aztec Manufacturing Co. in Carson City, Nevada.  They do a great job and the price is quite reasonable.  These are on an exchange basis and you will need to send them your original frame.   The Aztec part number for a milled frame for the Kato F3/7 is TM3008.

With the A units, there is a light board that can be used to connect the decoders red and black wires to the frame but what about the B units that don't come with a light board ?  Here is the method that I use.

Start by drilling a hole with a #50 bit just behind the pocket on each half of the frame. Drill to a depth about half way through the frame.  The hole should not hit the hole already in the frame that is for the screw that holds the frame halves together.

I use a small table top drill press that I purchased from Micro Mark.  Because the fuel tank part of the frame would make it hard to hold the frame square, I use a scrap of plywood to support the rear part of the frame.

Then tap each hole with a 2-56 tap.  Kadee part number 246 includes both the drill and the tap.




The motor brush to frame contacts that are in each Kato engine made great electrical mounting rings.  I find them handy for a number of projects and  save all of the I remove when doing installations.

This is the method I use to remove the motor brush to frame contacts on all Kato locomotives. Lay the motor on edge on a flat surface.  Using a flat blade jewelers screw driver, gently pry the brush holder up using the edge of the motor housing as the fulcrum. 

Cut the wires of the decoder to the following lengths:

Red / Blk / Yel / Blu / Wht = 1-9/16"
Gray = 1-5/16"
Orange = 1-7/8"

Solder the removed brush caps to the orange and gray wires, and the removed brush to frame contacts to the red and black wires.

Re-assemble the motor brushes with the decoder wires now attached to the brush caps.

Then place the motor, worm gears, and bushings into the right side of the frame.  Lay the orange motor wire into the slot on the right side of the frame that has milled for this purpose.  Take special care that the motor mounting rings are seated correctly into the frame.  Last install the two black shoulder washers.

Connect the left side of the frame together with the right side again being careful to correctly seat the motor mounting rings.  Then install the nuts and bolts that hold everything together.  Lay the decoder in the pocket that's milled into the top of the frame, attach the red wire ring to the the hole on the right side frame and the black wire ring to the hole on the left side frame with 2-26 flat head screws.  Lay the wires out flat in the milled groove down the middle of the frame and secure with scotch tape as needed.

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