TCS M1 in an Atlas GP7

Yes, this is yet another type of Atlas GP7 installation.   This installation follows an older technique that I don't use much anymore but in this case the model already has a Richmond Controls lighting unit installed and the goal is to continue to use it being controlled by the DCC decoder.

Richmond Controls of Richmond, Texas has been providing small lighting modules for model railroaders for many years.  Features may include constant brightness head lights, MARS lights, simulated rotary beacon, and other similar features.  For more information about Richmond Controls check out their web site.

This photo shows the Richmond light module on the left at the short hood end of the frame.  It's input is wired to the standard LED board on the long hood end to get contact to the frame.

First I wanted to verify for myself that the Richmond light module current draw was within what the function output of the TCS M1 decoder could provide.  The current draw was between 5.5 and 6.1 ma depending on the cycle of the rotary beacon.  This is well within the stated 100ma rating for the M1's function outputs.

A variable DC power supply was used for this test and the current draw did not change much between 6 and 12 volts.


To start this installation, the mechanism will need to be fully disassembled.

Normally on a straight forward DCC install on this model, I would have used a TCS CN-GP decoder without frame modification.

In this case to have room for the Richmond module I went back to my old method of using the TCS M1 wired decoder and a frame milled by Aztec Manufacturing.

This particular model is notorious for being noisy.  This has been traced to vibration of the inner bushing of the worm gear assemblies.  The assembly will support itself between the outer bushing and the flywheel so the inner bushing can be removed.  While this is apart for decoder installation is a good time to do this.

I did not invent this technique myself, but read about it years ago in N Scale magazine.  Here is a PDF reprint of that article.

To remove the inner bushing, first pull off the hex shaped part from the end of the shaft then remove the bushing and put the hex part back on.  The hex part must be a tight fit on the shaft as it is what interfaces with the flywheel.  I will normally use adhesive such as E6000 to secure this part to the shaft.

Tip:

If you ever have a locomotive where one or both sets of wheels don't turn when the motor is running, check this or it's equivalent part for being loose on the shaft.

The decoder wires are cut to the following lengths:

Black / Red = 2 inch
Orange = 1-1/8 inch
Gray = 1-5/8 inch

The White and Blue wires can be left alone for now.

As with many of my other installs, I file a groove on the side of the motor body for the longer of the motor wires to reach the bottom of the motor

One of the original LED boards is cut off so that there is just enough circuit trace sticking out from the frame to solder the red and black decoder wires to.  This is then installed at the short hood end of the mechanism.

The Richmond Controls module is then attached to the frame in remaining space with either double stick or adhesive.

The yellow is cut to a length that will allow it to be folded over the decoder and connected to the cathode side of the T3 size LED.

The blue wire from the decoder is cut a bit shorter than the yellow wire and then spliced with the section of blue wire that was cut off.  Both are then connected to a 680 ohm 1/8 watt resistor.  The resistor is then connected to the anode side of the LED.  Heat shrink tubing is used to cover these connections.

The remaining blue and white wires from the decoder and the red and black wires from the Richmond module can now be cut to a length that they will meet and can be spliced.  A 1000 ohm resistor was placed in series to hopefully prevent any over voltage to the Richmond module.  Splices are contained within small heat shrink tubing.


When the body is placed back on the mechanism, care must be taken with small wires to the rotary beacon.

Also, it is best to check the coupler height for both ends of the locomotive against a Micro-Train reference.  This the body of this model is a loose fit on the frame and if the body is sitting too low it can cause coupler height problems and the bottom of the body hitting the rails.  It may be necessary to place shims made from polystyrene strips on the inside of the top of the body.

Recently I've been learning how to work with YouTube a little bit and thought a good way to end this post was with a short video showing the simulated rotary beacon on this model in action.

TCS M1 in an Atlas Master Line GP38-2

I recently did an install on one of the more recent releases of an Atlas GP38-2 using the TCS M1 decoder.  While this install is similar to other installs I have presented using a wired decoder instead of a board decoder I discovered some differences that made it worth it's own post.

After dis-assembling the mechanism I discovered that the motor had a different type of brush holder than those found in most Atlas models.  This model uses the Kato style of brush holder with a separate cap.

The plastic motor saddle had also changed.  Because the brush holder with cap sits flatter than the one piece type, the saddle had a block on both top and bottom.  I found it necessary to remove the top block with a file to get a good fit.

The board requires the same type of preparation as the board did on the Atlas Master Line GP7 that I did about a year ago.

For more for details on how prepare and wire the decoder to the board check HERE.

This model comes with the little spring clips on the original LED board.  I've never had much luck with these and the ones on the board fell off so I used the solder method to thicken the board for a good fit into the frame.

After re-assembly the mechanism looks like this photo.  The model I did was actually a GP38-2 but a master line GP38 should be an identical mechanism.  I test ran this model with an earlier release GP38 and the speed of this new motor seem to match the older release perfectly.

TCS ASD4 in an Atlas Master Line GP7

About a year ago I presented an installation where I used a TCS M1 decoder on an Atlas Master Line GP7 which is intended to take a board type decoder but does have room for wired decoder using the existing PC board.  To see that post click HERE.  Recently I was asked to install TCS ASD4 board type decoders in several similar models so I thought it would be good to present that type of installation as well so someone could make the comparison.

What happens sometimes with these decoder board type of installations is that the contact tabs from the motor don't line up with the slots on the board.  The photo shows how I check for this, lining up the frame to board contacts first then checking alignment of motor contacts.




It's not hard to fix this problem by hard wiring the motor contact to the board.  I use scraps of orange and gray wire left from wired decoder installations.  It does not matter which color wire is used as long as the wire from the bottom brush goes to the forward slot and the wire from the upper brush goes to the rear slot just as the tabs would if they lined up properly.

Cut the tab from the lower brush short and solder a wire to it, then slide a short length of 3/32" heat shrink tubing over it.

For the top motor brush first remove the brush holder and take the tab off.  Then solder the other wire to it.  When cooled re-install holder with spring and brush into motor body.

After both wires are attached to the motor assembly, slip them through the plastic motor saddle as the saddle is pressed onto the motor.  When that's all done the finished assembly should look like this photo.

Another issue with the board type decoders is that they sometimes fit loosely in the frame.  On this one I fixed they by adding a small amount of solder to the contacts on the bottom side of the board.  On this model I found that a thickness of .030 was about right to get a snug fit.

Press the board into the right half of the frame, it should fit snugly. On these Master Line GP7 and 9 models, there may be a small plastic button.  That goes into the right side frame as shown here.

When everything is all put back together it should look like this.  The wires need to lay in between the frames.

A nice thing about this decoder board is that is has big solder pads to easily connect extra lighting functions.



In some future post I will show some ways to use these additional functions.

Kato SD80Mac slow running

At a recent train show one of my buddies from the Ntrak club I belong to asked me to take a look one of his Kato SD80Mac locomotives.  His complaint was that while it did run, it was slower than other identical locomotives.  I verified this on my test layout and it seemed to get worse the more I ran the locomotive. I then took the shell off to test the motor for current flow and this is what I found.

Apologies for this blurry photo.

The kapton tape was coming into contact with a rotating part of the motor as indicated by the arrow on both sides preventing the motor from turning freely.  This put an overload on the decoders motor output.

This photo shows how the installation should look. The kapton tape comes over the side of the frame on each side and stops before reaching the open part of the motor.

This type of installation is common to several Kato models.  They are generally an easy DCC installation but it is a good practice to always check for free rotation of the motor when doing an install.

When I put the decoder on my test fixture, the voltage on the motor output of the decoder was zero when connected to the test motor but was normal with no load. There was no sign of anything burned on the decoder.  A reset was programmed into the decoder but this did not clear the problem.  In this case the decoder needed to be replaced.

Before installing the replacement decoder the current draw of the motor was measured by connecting the motor directly to my bench DC power supply as shown in this photo.  It is rare but I did once see a defective motor cause a decoder to burn out and that became the first post on this blog.