Spectrum 2-8-0 DCC

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Installing Digital Command Control in the Bachmann Spectrum 2-8-0 Consolidation Steam Engine.  It's as easy as 1-2-3. 1. Open the tender    The tender shell is held by one screw, centred just behind the front truck, and by two plastic hooks extending from the back of the shell down through the chassis of the tender. Open the tender by removing the screw and gently tilting, lifting and wiggling the shell. The hooks may be tight in their holes but with patience they will come out. Photo 1 tender screw 2. Install a  decoder    There is enough room under the dummy coal load for many HO size decoders.  An MRC AD310 (obsolete) is shown.  A Digitrax DH123P is somewhat smaller and today is an excellent choice.  The opening below the coal load is large enough to allow the decoder plug to pass into the space below.  The coal load is held in place only by friction and simply lifts out of the tender.  The Digitrax DZ123PS is smaller still and will fit in the lower part of the tender.  Once the decoder is in place, remove the dummy plug from the socket on the adapter board near the rear of the tender.  Sometimes it helps to pry up the plug gently with a jeweller's screw driver just to get it started, then pull it straight up. Just in case you want to restore the engine to dc operation at some later date, save the dummy plug by taping it inside the tender shell. Plug in a decoder with pin 1 of the plug in pin 1 of the socket. Pin 1 is often identified on the plug with a dot or triangle and if standard colour coding is used, pin 1 has the orange wire connected to it.  Pin 1 on the adapter board can be seen in Photo 3 below. If your decoder has no plug, install one. Refer to the photo and chart below for pin out and functions. In a pinch, it is possible to use the dummy plug by first removing all the solder, then clipping the jumpers between the pins. This is best done with the plug installed in a spare socket to keep the pins from falling out of the plug when you heat it. If you have no spare socket, it is possible to do this job with the plug installed in the tender socket but great care must be taken not to damage the socket or unsolder it from the printed circuit board. If in doubt, obtain a plug or wiring harness through your dealer. Photo 2 - disassembled tender with decoder under dummy coal load. 3. Reassemble the tender, making sure the wires are all tucked in and not caught between the body and frame.  Program your decoder according to the manufacturer's instructions, and enjoy your train!   Photo 3 - interior of tender of second release Bachmann Spectrum 2-8-0 Consolidation pin function standard colour 1 motor "right " connection orange 2 rear light yellow 3 no connection n.a. 4 left wheels black 5 motor "left" connection grey 6 front light white 7 lights common blue 8 right wheels red Known Issues with this and other Bachmann HO steam engines: Incorrect Headlight Operation.  This occurs only with the first release engines.  The second and subsequent releases of this engine should work correctly with the above installation once the decoder is programmed normally. The second release can be identified inside the tender by the presence of a resistor at A in the Photo 3.  This resistor (a light tan colour with four bands) is connected above the board to a diode at B. There is no resistor at this location in the first release. If you have a first release engine, the decoder will have to be programmed to reverse the motor polarity. With Command 2000, this means pressing button 6 in step 5 of the programming sequence. With Digitrax, etc., it means setting CV29=07.   Poor, erratic DCC speed control caused by a noise filter on the adapter board that can affect the decoder, even though the wheels, wheel pickups, and rails are clean.  Typically, the engine runs fine on d.c. but runs erratically on DCC.  Needless to say, any tests to compare d.c. operation to DCC operation should be performed one right after the other on the same track and under the same conditions.  If these tests show operation is erratic only with DCC, the filter capacitor should be disconnected and testing with DCC repeated.  The capacitor in question is labelled C1 on the board and is visible at the top (front) of the board in Photo 3.  Snipping one lead half way between the capacitor body and the board leaves two ends that can later be reconnected if desired - just be sure to bend the capacitor up a little so that the cut ends cannot touch.  For background information, read on. The noise filter on the adapter board consists of two coils and a capacitor, C1.  The two coils are in series with the two motor leads and capacitor C1 is in parallel with the motor.  There is also a place for a second capacitor labelled C2, but no capacitor is present.  If it were, C2 would be in parallel with the headlight.  Bachmann has not been very forthcoming about the reason for this noise filter, but the author speculates that it may be a requirement in Europe where population densities are higher and the chance of your trains interfering with your neighbours' T.V. sets is greater.  Many engines built in Europe have similar noise filters to keep the electrical noise generated by arcing  motor brushes away from the rails which could broadcast those noises as radio frequency interference. While the filters are probably not required in North America, it is likely easier and cheaper to manufacture all the engines to international standards than produce different batches for different local markets. Whatever the reason, the filters are there. Just how the filter affects the decoder is also open to speculation.  In general, pulse circuits (like decoders) do not like to power reactive circuits (ones that contain capacitors and coils.)  Capacitors conduct high frequencies very well and the fast rising leading edges of pulses contain lots of high frequencies.  This means that the output of the decoder may be instantaneously overloaded hundreds of times a second.  This could interfere with any output protection circuitry in the decoder.  Ideally the series coils would extend the rise time of the pulses and reduce the problem, if the load were resistive.  But the load is not resistive.  In fact, the coils in series with the capacitor form a series resonant circuit which has almost zero resistance at its resonant frequency. Some of the energy in the decoder output pulses  may be at or near that resonant frequency, again causing overload.  In either event, removing the capacitor from the circuit solves the problem. One problem remains - warrantee.  Does disconnecting C1 negate your warrantee?  The author has been unable to get a blanket ruling from Bachmann on this, so it looks like this is being decided on a case by case basis.   Contacting Bachmann Service Bachmann's Service Department is available from 8:00 am to 4:00pm Eastern. They are closed between Noon and 12:45 for lunch. Customer Service for all scales can be reached at 800-356-3910. Each department has its own extension.      Parts: Ext. 11 and 17       Technical Support: Ext.12       Repair Status: Ext. 13       Customer Service Manager: Ext.18      Notes - these notes apply to DCC installations in general and not just to this engine. The motor right connection is the motor wire or terminal that would connect to the right hand wheels if the engine were wired to operate on dc. It is also called the + connection because it is positive polarity when the engine is moving forward. Likewise the motor left connection is the motor wire or terminal that would connect to the left hand wheels if the engine were wired to operate on dc. It is also called the - connection because it is negative polarity when the engine is moving forward. The lights common connection connects to both front and rear bulbs or LED's. In the case of LED's, it connects to the anode or + connection. The front light and rear light connections connect to the front and rear bulbs or LED's, as required. If bulbs are used, these connections go to the sides of the bulbs not connected to the lights common. If LED's are used, they connect to the cathode or - terminals, typically through a resistor. The front light and rear light connections may be connected together to operate a front light, a rear light or both when these lights are to operate in both directions. Alternately, they may be connected together through a resistor (value as required, 100 to 1000 ohms) which will cause the light to dim but not extinguish when the opposite direction is selected.     If you liked this article, let us know.  If you didn't, let us know why.  Your feedback helps us improve our site. Contact Us

In Reply to: DCC problem posted by D White on December 23, 2001 at 17:15:02:

: I have a Spectrum Consolidation with a decoder made by NCE plugged in. I am having problems
with speed control and was told on another forum that the reason is an RF filter on the Bachmann
circuit board, which could be removed. Can this be done, and what components need to be
removed?

Dear D. White,
It is our policy to refer DCC questions to the manufacturer of the system or decoder, as I did
below. As far as modifying our circuit board, before you do so I would check with service to see
how this would affect your warranty.
Enjoy your trains!
the Bach-man