N Scale Bachman B23-7 Decoder Install

Tad May 23, 2021

  1. Tad

    Tad TrainBoard Supporter

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    This is how I installed a TCS M4 decoder in a Bachmann B23-7.

    Now some folks might be wondering why you would even want to install a decoder into an older Bachmann diesel locomotive. These were originally released in 2006.

    Whether you know it or not, Spookshow gave these an “A.”

    http://www.spookshow.net/loco/bachb30-7.html

    One of the roads that I model is the Missouri Pacific. After reading Mark’s review I picked up a Bachmann # 61355 Missouri Pacific B23-7 # MP 4637 for $20-25 a while ago when the LHS went out of business. My example is actually a good, smooth runner and pulls very well. Sorry, I can’t tell you exactly how many cars that it pulls.

    To my knowledge, there has never been a drop in decoder made for this model.

    I recently acquired a TCS M4 decoder for $19.99 delivered. I figured that this would be a good opportunity to upgrade this locomotive to DCC.

    This is a fairly straightforward and uncomplicated install.

    Maxairedale posted a thread here on Trainboard about 10 years of an install that he did on this same type of locomotive using a Digitrax DZ123.

    https://www.trainboard.com/highball/index.php?threads/decoder-for-bachmann-b23-7-b30-7.51036/

    Installing a TCS M4 is pretty much exactly the same procedure that he used.

    This is the locomotive on my workbench.

    upload_2021-5-22_23-1-29.jpeg

    In the instructions that come with the locomotive, it states to remove the weight under the rear of the circuit board and install the decoder of your choice. On the right rear of the locomotive, you take out one small Phillips head screw and the weight slips right out.

    You have to remove the two copper jumpers or as the instructions call them, “dummy plugs,” to prepare the circuit board. These jumpers can be seen in the above photo on the near edge of the board just aft of the motor. Simply hook them with your fingernail or something and they pop right off.

    There is also a diagram in the instructions that tells which color wire goes to which contact point on the circuit board. The contacts are numbered on the circuit board. There is no # 3.

    upload_2021-5-22_23-14-34.jpeg


    You have to “unclip” the circuit board from the frame to be able to work on it. All this takes is to hook your fingernails on one side of the board and move it to the opposite side of the frame and lift up. It is easy and doesn’t require very much force at all.

    This is the wires “loomed” or threaded through the proper holes in the circuit board.

    upload_2021-5-22_23-21-26.jpeg

    This decoder has purple and green wires that are not used in this installation. I trimmed them off but left some length “just in case” but I’ll probably never need them.

    I trimmed all of the wires to one inch in length. I then aligned the decoder with the rear edge of the circuit board and, one at a time, trimmed and attached the individual wires to the circuit board.

    upload_2021-5-22_23-29-41.jpeg

    Using a toothpick, I put a very small amount of rosin paste through the contact hole on the circuit board and on the stripped tip of the wire. I stripped about 1/16” of insulation off of each wire. I then fed the wire into the contact hole from the bottom of the board. I used a fine tip on my soldering iron and very small diameter solder. It only took about a second or two with the iron to attach each wire. The contacts are small so be careful to not use too much solder to prevent bridging between the contacts and causing a short.

    After attaching all seven wires, I folded the green and purple wires over the decoder and used Kapton tape to fix the decoder to the rear of the frame. I then reinstalled the circuit board by snapping it back into place.

    upload_2021-5-22_23-38-27.jpeg


    This is the locomotive on my test board.

    upload_2021-5-22_23-41-36.jpeg

    Believe it or not, it worked just fine.

    And with the shell reinstalled.

    upload_2021-5-22_23-45-21.jpeg

    It ran fine on my test loop, too. Now I’ll just have to speed match it and fool with the CV’s to tweek it a little.

    So, for less than $50 total, I have added another DCC locomotive to my fleet.
     
    Last edited: May 23, 2021

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