(acetal resin) couplers are required. Use a Kadee long-shank No. 26 coupler on the front and a medium-shank No. 28 on the rear.
Better performance may be obtained by mounting Kadee couplers in their own “draft gear” boxes. The existing frame mounting tabs are too low to per- mit properly mounting new coupler box- es underneath in the usual way. Howev- er, by filing down the top surface a bit and using the existing bottom dimple as a starting point to drill a number 50 hole and tapping it 2-56, a shortened Kadee No. 5 coupler box mounted above the tab will result in the correct height. If Kadee No. 26 and 28 couplers are al- ready on hand, they may be re-used in the new boxes. Since the boxes them- selves are insulated, equivalent metal couplers may be substituted. If the model is to be a standard d.c.
engine, and assuming the motor brush- es are in good shape, wire in the new headlight bulbs. With 12-volts d.c. one 680-ohm, .5-watt dropping resistor is required in series with each of the 1.5- volt lamps. If a DCC decoder and speaker is to be installed the simulated fan blade mechanism and weight may have to go. The original headlight and associated diode circuitry behind the cab must be removed, but its lower mounting bracket makes a perfect holder for a new decoder. I chose a Soundtraxx Tsunami TSU-
AT1000 sound decoder, No. 828044; it produces the correct Alco 251 V12 sounds and fits within the clips that originally held the diode circuit cover.
11.
A piece of double-sided tape is suffi- cient to secure the rear of the decoder above the motor. The orange wire con- nects to the lower motor terminal and the gray goes on the upper (on the far side in the photo). A small piece of Kap- ton tape will insulate the lower motor terminal. The photos show that the rear truck power contact has been trimmed shorter and the rear black de- coder wire soldered onto it. Attach the electrolytic capacitor to the frame with silicone adhesive, and trim its wires to length and re-solder them to the de- coder’s printed circuit board. I used miniature electrical connec- tors to make up the speaker and body lighting connections. They are manu- factured by Molex under their trade name PicoBlade®
and are available
from Digi-Key in a variety of pin counts. Liquid electrical tape applied with a toothpick may be used to make a strain relief for the wires. Although this step requires a bit of extra work, the connectors are very convenient. The connections for the new, dual headlights in the body are carried through the rear-most connector, but the existing “light pipes” leading to the number boards are illuminated from the original headlight location. Replace the original 14-16 volt lamp with an- other 1.5-volt Miniatronics bulb lightly glued into a No. 54 hole drilled in a piece of 3/16” wooden dowel and fit into the original lamp location. Connect this new bulb to the F5 decoder output with a 680-ohm, .5-watt resistor in se- ries soldered directly to the decoder’s printed circuit board. A QSI high-bass, 8-ohm, 1-2 watt speaker was selected for this model. It fits nicely under the radiator fan screen in place of the simulated blade
mechanism. Make up a speaker enclo- sure from styrene. A trial and error project, it should slide between the pair of radiator shutters in the carbody and will also help retain the parts in place with gentle side pressure. For any DCC project involving re- wiring an existing model and adding new features, it is worthwhile to sketch out a wiring diagram, as shown. It does- n’t have to be a work of art, just accu- rate. Similarly, when documenting the CV settings, especially those changed from their factory defaults, making a list or chart is a good practice. My set- tings are given here. Finally, having notes available on what you did will save time on future, similar projects. Thorough testing of all decoder func-
tions, with the speaker, headlight and back-up lights temporarily plugged-in via their connectors should be done now. A very nice, accurate cast-resin fuel tank is made by Jay Rotsch,
jay-
rotsch@aol.com. It is a perfect slip-fit over the frame in place of the existing FA-2 fuel tank. The new fuel tank needs to be left removable to permit fu- ture access to the four frame-mounting screws. A dab of silicone adhesive or a small piece of double-sided carpet tape placed in the bottom of the resin cast- ing after final assembly will do the trick. (Jay also makes a combined side grille and radiator shutter casting which can be used as an alternative to the metal Farr grille described here.) To help compensate for the loss of the existing die-cast weight displaced by the decoder, put self-adhesive tire- balancing weights in .5 and .25 ounce sizes on the front and rear of the frame. Before wrapping up the chassis work, clean the wheel faces and paint them Grimy Black; a micro-brush is
11. A Kadee No. 26 long-shank coupler was mounted on the front of the unit. 12. A medi- um shank No. 28 coupler was used on the back. Note that the Kadee boxes have been modified so that the couplers are mounted atop the frame mounting tabs. 13. Here is the completed, DCC-equipped chassis with a Soundtraxx Tsunami sound decoder. A piece of double-sided tape holds it above the motor. Note the miniature electrical connectors used for the speaker and lighting connections. A QSI high-bass speaker placed in a styrene enclosure will be mounted between the radiator shutters in the carbody.
13. 12.
RAILROAD MODEL CRAFTSMAN
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