Bachmann Spectrum H16-44 DCC

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Installing a decoder in a Bachmann Baby Trainmaster.  The H16-44 is a typical Spectrum split frame engine.  This approach should work as well with similar engines. This installation was done several years ago using an MRC AD310 decoder but today the slightly smaller Digitrax DH123D would be a much better choice.  Photo 1 In this photo and all following photos, the front (cab end) of the engine is to the right. Remove the mechanism from the shell (4 screws.) With the engine upside down, the 4 shell screws are below the four wheels closest to the fuel tank. Also remove the fuel tank (2 screws.) Keep the special fuel tank screws with the fuel tank (all the other screws are interchangeable.) Remove the light board (2 screws.) Cut the center out of the light board using a model saw or cutting wheel in a Dremel tool. Do not try to cut it with rail nippers, tin snips, diagonal cutters, scissors or other shearing tools. The phenolic circuit board material will shatter. The light board at the bottom of the photo is marked with black lines where the cuts are to be made. Note that these lines are about 1/8" toward center from the mounting holes.   Photo 2 Examine the mechanism frame, which is made of two mirror image pieces. This split frame design is a common feature in Bachmann Spectrum engines. The two halves are held together by three screws which thread into plastic Tee nuts in the other half of the frame. The two halves are separated and insulated by plastic washers fitted on the Tee nuts. Before taking the frame apart, scratch a mark on the motor to show which way is up. The author used a "T" for top. Some motors are marked by the manufacturer. This one had an inverted V at the bottom on the other side. But do not count on there being any markings. Remove the 3 screws and gently pry off half the frame. In photo 2, the right-hand frame half has been removed, leaving the motor, trucks and gear towers in the left-hand frame half. The screw driver points to the tab that is attached to one of the brush holders and contacts the removed frame half for power pickup. That makes this the right-hand motor brush, which will connect to the orange decoder wire.   Photo 3 Remove the right-hand brush retainer cap, being careful that the brush spring does not fly out. Solder** the orange decoder wire to this cap. In practice, it is easier to solder the cap to the wire. Tin the wire. Pick up the cap with a fine pair of tweezers and tin it lightly. Add a tiny bit of flux, then bring the cap up to the wire and touch them with the soldering iron. Before reinstalling the cap, cut the long tab off the brush holder, using a very small pair of side cutters or a finger nail trimmer. Snap the cap back on the brush holder, then solder the grey wire to the left hand brush holder in a similar manner.  In the photo, the cap is seen hanging above the brush holder prior to being snapped back into place. The brush spring can be seen peeking out of the holder, all ready to fly into space if it is compressed then suddenly released.  **Check our Soldering Primer for tips on soldering.   Photo 4 Install the motor back into the frame half and check for clearance between the brush caps and the frame. There must be no contact and no possibility of contact from the frame to the brush caps or the bared wire attached to them. If things are a little close, buzz out a bit of metal using a spherical burr in a Dremel tool.  To be on the safe side, you can add a wad of tape or a dab of silicone bathtub sealer between the brush caps and the frame.  This will prevent decoder damage if a brush cap should happen to pop off. In this photo, the "T" scratched on the motor by the author is visible at the top of the motor.   Photo 5 Now comes the fun part - reassembling the mechanism. The motor should already be back in place. To install a truck, first engage the end of the drive shaft "A" in the end of the motor flywheel, turning the flywheel as required to align the slot with the horns on the ball on the end of the drive shaft. Once the drive shaft is engaged, insert one side of the tower retainer "B" into the frame half. Then lower the truck into place while making sure the pickup ring stays below the frame half. The pickup ring we are talking about is the twin to the one shown at "C". It will try to slip up inside the frame. Your job is to make sure it stays below the frame. Next install the second truck. If you find the first truck wants to pop out while you are installing the second, try propping up the frame half with some washers so that it sits level while you are working. When both truck are in place, check that the Tee nuts and washers are still in place at "D", "D" and "D", and that the fuel tank nuts are in place at "E". Then lower the other frame half into place, keeping the pickup rings below the frame. When the frame halves are together, install the 3 holding screws. It will be necessary to poke the Tee nuts through from the other side and hold them in place while installing the screws. Sometimes it is necessary to turn the Tee nuts back and forth with a fine pair of tweezers while pushing them in place. Fortunately, the Tee nuts can be pushed and the screws installed one at a time.  Photo 6 There are several methods of connecting the input wires of the decoder but this method is probably the easiest. On the author's engine, the screws were installed from the right-hand side, so the red wire was slipped under a screw at "A". If the screws had been installed from the left-hand side, the black wire would have been installed this way. To assure good contact with the frame, remove the screw completely and scrape the metal clean and shiny before reinstalling the screw. Twist the wire stands tightly together, wrap them one turn around the screw, and snug the screw down, but not so hard as to strip the plastic Tee nut. The other input wire must connect to the other frame half. This was done on the author's engine at "B", where the Tee nut was removed to the other frame half. You may find that you have to file a slight chamfer on the end of the Tee nut in order to install it with the frames fastened together, and you will have to be careful not to disturb the insulating washer while the Tee nut is not there keeping it in place, but it is doable. You may want to test run the engine at this point. Just be sure that neither the unconnected wires nor the bare connections on the decoder can touch either frame half during the test.   Photo 7 The end pieces of the light board were used to hold the original 12 volt bulbs in place. This particular light board was wired for directional lighting but not constant lighting and could be identified by having two diodes, one in series with each lamp. Other Spectrum engines may use constant lighting and will have more than two diodes. The lamps on these boards are typically 2.5 volts and are not suitable for direct connection to DCC decoders. They can be replaced with 12 volt grain-of-wheat bulbs. The front board was connected to the white wire and to the blue wire. The rear board was connected to the yellow wire and to a jumper wire connected to the blue wire on the front board. After the photo was taken, the light shield over the front board was reinstalled and the rear board was insulated with a strip of masking tape.  There was not enough vertical clearance to use foam tape so the author used double sided carpet tape to hold the decoder in place. This material does not hold well but with everything else well insulated, there is little danger even if the decoder does slip around.   Photo 8 Canadian Pacific 8552 pulls a string through James River on the author's Lorraine Valley and James River Railway.