My First Decoder Installation

[burke19]

I'm getting ready to install a decoder in a Bachmann GP-40. The loco is around 5 or 6 years old, and came from a train set. I don't have any of the packaging, and have no idea if this loco was "DCC - ready" or not. Now, I've looked over the wiring, and as near as I can tell, the electrical seems to be isolated from the frame already. In fact, here is a link to a pdf of an exploded view of the loco: http://www.bachmanntrains.com/home-usa/dwg/dwgs/H635X_IS005.pdf This is one of those situations where I'm 95% sure that the frame is already isolated out, but I thought I'd go ahead and ask the dumb question before I end up screwing my new Tsunami decoder. So, as near as you guys can tell from the diagram (or from past experience if anyone has one of these models), is the motor isolated from the frame, or am I missing something? Thanks!

[jeffrey-wimberly]

One way to tell if the motor is isolated from the frame is to follow the wires from the motor. There should be two wires going from the motor to the lightboard. There should be four wires (red and black) going from the lightboard to the trucks. I there is only one wire coming from each truck and one wire going to the motor then the motor is not isolated. Some have two wires to the motor but only one wire on each truck, others have one wire on the motor and one wire from each truck. These are commonly known as 'hot frame' locos. The frame serves as a carrier for part of the electrical path. When in doubt, check with the multimeter.

[JoeinPA]

 From the diagram it sure looks like the motor is isolated.  BUT I agree with David that it would be wise to check it out with a multimeter.  If you don't have one get one.  If you are going to get deeper into DCC and more installs you will need one and find it to be indispensible.

 

Joe

[locoi1sa]

 How does this loco run? How many amps does it pull stalled and slipping? You said it came from a train set. Most locomotives from sets I have seen are poor runners and cheaply made. A tsunnami is a very chalenging first decoder instal for sure. Why not install an inexpensive motor and light control decoder first? That way if something is not right it would not be so costly. Try a TCS decoder. They will warranty it even if you mess it up.

  Besides a multimeter other things to make decoder installs easier is wire strippers, 25 watt or lower soldering iron, wire cutters, heat shrink tube, thread for tying wires, double stick tape, .015 diameter solder, extra decoder wires(30 gauge), and Kapton tape.

     Good luck

    Pete

[burke19]

The loco actually runs really well. Plus it has sentimental value. Anyways, I went ahead and tested the motor with my multimeter. I never actually paid attention to the ohm function (I've only ever used it to check household circuits to see if they're live). The motor was isolated from the frame, but the motor connections were so close to the frame that I decided to take steps towards further isolation. Anyways, I managed to get the decoder & speaker hooked up last night, and I have to say, I'm quite proud of myself. Everything works great, and I can't get over how awesome the sound is! I never thought I'd be that interested in having sound on my layout, but now I think a tsunami is going to become a pre-requisite! Now all I have to do is figure out how to cram everything under the shell - which should be fun. Anyways, thanks everyone for the tips - now I know to always take extra precautions to make sure the motor & frame are isolated.

[donhalshanks]

Sorry, but maybe a dumb folowup question.  Using the multimeter, how does one use it to test for isolation of the frame?

Thanks, Hal