Sunday, November 21, 2010

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.

Friday, November 19, 2010

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.


Sunday, November 14, 2010

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.