Friday, February 10, 2012

TCS Z2 in a Micro Trains FT

Anyone who has followed this blog will notice that I am a fan of TCS decoders and use a lot of their Z2 model.  I have found it to be a great decoder, small enough for many applications and robust enough for any N scale engine.  TCS does not make a board type decoder for the Micro Trains FT so I wanted to see if I could wire in a Z2 and found it to be a relatively easy install.

The first step is to remove the shell from the frame.  On the front of the A unit, remove the screw then pull the coupler out forward.

On the rear of the A unit and both ends of the B unit, removed the coupler and mounting frame together.

After removing the shell, the LED light board is exposed.  Just behind the board there is an indent in the frame that is large enough for a wired decoder.  Remove the black light shield and then the board. That's right, the frame won't have to be taken apart on this one.

The boards in the A units will have the LED along with a couple of other components.  Remove the two that are pointed out in this photo.  They were needed for the DC operation of the bright white LED but will not be needed for the decoder function output. 

The board from a B unit will not have any components on it at all so this step can be skipped.

I have found the quickest way to isolate all the parts of the board is to cut a notch on each side of the board through the two circuit traces.

This step needs to be done on the boards for both the A and B units.

Here are the lengths I cut the wires to. 

Blue, white, gray, yellow = 1"
Orange = 1-3/8"
Red, black = 1-5/8"

Kapton tape is best to use for insulating the frame but does not stick to the frame as well as Scotch tape.  I clean any oil off the frame of course, but then I use a layer of Scotch tape first then apply the Kapton tape.  It sticks very well to the first layer.
Connect all of the decoder wires as shown in this photo.  This can be done either before or after the board is re-installed in the engine.  The photo shows an A unit.  The B unit won't need the white and blue wires.

Special note on the B units

FT's were run with the B units oriented backwards in relation to their associated A unit and were often draw bared together.  This is noticeable by the two sets of ladders, the offset of the wheels and fuel tank, and the dynamic brake vents on the roofs of the ones that had dynamic brakes.  The PC board in the Micro Trains FT B unit is oriented in the opposite direction as the A unit.  This would have not mattered running DC but with DCC we must have a front and a back end to each locomotive.

Here is a prototype photo showing an A B set arranged this way.
This photo showing an A B set with the shells next to a pair of mechanisms shows what is going on.  This can be corrected by programming the B unit for reverse operation

CV 29 = 07 for 2 digit address
CV 29 = 27 for 4 digit address

Wednesday, February 1, 2012

TCS CN-GP in an Atlas GP7

Between 1995 and 1997 Atlas did several releases of N Scale GP7's and GP9's based upon this mechanism.  The TCS CN-GP decoder is a perfect choice for these. 

The frame requires some very minor modifications that I do using a Dermal rotary tool with cutoff wheel.  The small ridges between the light board clips at each end will need to be removed and also a notch needs to be made on the left side frame at the point shown in this photo.
On some GP9 releases the frames have interlocking tabs.  If you have one of these just snap off the upper tab.  This will create the space needed for the motor wires.

In this photo all of the frame modifications are done.  Also shown is the plastic motor saddle with a  notch on the top.  The notches on the frame and the saddle are needed for the motor wires.

Remove the brush caps from the motor and remove or cut the contact tabs.  Then remove the orange and gray wires from the decoder and solder them to the brush caps.  File a slot big enough for 1 wire on the left side of the motor.  With the orange wire going to the bottom, re-install the brush caps with wires and motor saddle.

Re-assemble the locomotive mechanism with the orange and gray wires going through the hole on the top of the left side frame and the plastic motor saddle.

Install the CN-GP decoder boards on the frame and connect the yellow, black, and blue wires as directed in the decoder instruction sheet.
Cut the orange and gray wires to the correct length and re-solder to the front board.  All wires should lay flat and not overlap on the top of the frame.

Re-install the trucks, contact strips, and fuel tank.

These Atlas GP7's were among the first N scale engines to have lighted number boards with the numbers already in them.  Because the LED they used was so dim, this feature was not really noticeable.

With the bright white LED's that come with the CN-GP decoder, this feature can now be fully appreciated as seen in the photo above.  You may even find it necessary to mask for paint the inside of the shell at the ends if the light shines through the shell.