Thursday, November 3, 2011

TCS Z2 in an Atlas GP40

The older version of the Atlas GP40 did not have any provision for a board type decoder.  The sure fire way to get a wired decoder into one of these is get the frame milled by Aztec Manufacturing.  I've done many of those and they work out fine but this time I wanted to do something different.

Here is a look at the stock GP40 mechanism.  Notice that the two LED boards are put in differently.  They are actually different boards.  There is room under the rear LED board for a small decoder such as the TCS Z2 if the LED itself was not in the way.

These are the modifications I made to the right frame half.  I found that without the slot for the wires on the top of the frame, the shell was not resting square on the frame.

This photo shows a side by side comparison of the original rear board and the one I made from a shorter board from another Atlas engine. The SMD LED is wired to the board with magnet wire and hangs over the end of the board. It is now clear to leave enough room for the decoder and sticks out no more than the original board did.

Both circuit traces to the frame contacts are cut so that this is isolated from the frame.  The yellow and blue wires will get soldered to the LED and resistor on this board.  On this board rather than drill a hole I made the existing opening longer so all the decoder wires could go through the opening.

The Z2 decoder wires are cut to the following lengths:

Gray = 2"
Orange = 1-1/2"
Yellow & Blue = 7/8"
Red, Black, & White = 2-3/4"

On the front LED board a hole needs to be drilled at the location shown in this photo.  The black and white wires are connected as shown.

The circuit trace gets cut the the same
location as is commonly done.  The red wire goes through the hole and is soldered at the point shown in this photo.  With this board being component side up this will place the red wire on the right side of the locomotive.

As I do with many installations I have filed a groove into the right side of the motor to contain the gray motor wire and secure it with a tiny amount of Walthers Goo.

Here is the completed assembly before re-installing the shell.  The wires will lay in the groove and can be secured with scotch tape. 

I found that the best way to get the shell back on was to follow the steps that are in this photo.  The important thing is that the shell is seated properly on the frame so that the body mounted couplers are at the correct height.