Aztec's HO Track Star cleans up

DCC and Micro-Trains coupler installation in an ER / Bachmann Baldwin Shark by Rod Schaffter
The excellent ER models Baldwin Sharks are now available again from Bachmann at great prices. However, converting them to MTL couplers has been problematic because of reliability issues with the recommended 1133 & 1134 couplers. Also, the locomotive is DCC ready, but the drop-in decoder is currently unavailable from Digitrax. This post describes how to add body mounted MTL couplers and DCC decoders. Coupler Installation Materials For the front of the A unit I used the coupler and pocket cut from an MTL truck (a 1025 would also work, but the larger box of the assembly removed from the truck fills the pilot opening better), and for the rear of the B unit I used a 1015 coupler. You will also need some Evergreen 0.020" x 0.250 and 0.050" x 0.100" styrene strip. To get close coupling, I used truck mounted short shank Unimates in the rear of the A and the front of the B, but 1015s could be mounted in those locations as well. Also needed are 00-90 coupler mounting screws, Walthers Goo, liquid plastic cement and a black Sharpie. Tools You will need the usual small screwdrivers, X-Acto knife, 00-90 tap, #'s 56 & 62 drills (the tap & drills are available from MTL, part # 988-00-121), pin vise, and rail nippers or a Zona saw. A Unit Front To prepare the mechanism, remove the carbody. Score the coupler mounting where it meets the truck body and nip off with nippers (Note-it will fly-wear eye protection!) or saw it off. On the front of the A unit, drill a # 62 hole about the width of the bit away from the front of the underframe, and tap it 00-90:

The coupler mounting area is about 0.02" too high, so cut a piece of 0.020 x 0.250 strip about 0.2" long and drill a #56 hole centered along the 0.250" dimension, and about 0.1" from one cut edge. Color it black with the Sharpie. Drill out the hole in the coupler removed from the truck # 56 and insert the screw. Put a tiny dab of Goo on the top of the box on the side away from the hole, and place the plastic spacer you made over the screw with the cut edge closest to the hole to the front. Put a dab of Goo on the spacer and screw the coupler on. Once the coupler is screwed on, cut the small locking tabs at the front of the coupler box off. Color the screw head black with the Sharpie:

B Unit Rear Remove the truck coupler mount as above. Cut a piece of 0.050 x 0.100 strip about 1/2 " long. Slowly and carefully grill a centered # 62 hole in the 0.050" edge of the strip 0.075" from one end. If it breaks through slightly on one side it will still work. Cut a piece of 0.020 x 0.250 strip 0.150" long and glue it cross-wise across the end of the strip with the hole drilled in it to form an inverted 'T' shaped assembly and let dry:

After it dries, extend the # 62 hole through the sheet and tap 00-90. Put a dab of Goo on one side of the 0.020" strip where it joins the 0.050" strip. Loosen the rear screw holding the frame halves together several turns, place a large jeweler's screwdriver between the frame halves at the rear and twist gently to spread the halves (an extra hand may be helpful here). Using the excess as a handle, gently insert the 0.050" strip between the frame halves, lining the back edge of the 0.025 strip flush with the frame, and pressing it up against the frame bottom. Tighten the frame screw:

Trim the excess 0.050" strip flush with the rear of the frame and color with the Sharpie. Screw on the 1015 coupler, using a small dab of Goo in the top. Replace the shells if you are DC, or go on to DCC installation: DCC Installation The DCC installation is based on posts by Nelson B at Trainboard.com, with some modifications. I used Digitrax DZ123 decoders-they work well and are dirt cheap (I got mine for $15 each in quantity), but I recommend testing them before you install them, as I have found a defective one, and Digitrax's warranty is void once you cut a wire. Also, I removed the stock yellow LEDs and added Richmond Controls Sunny White LEDs. (I purchased the decoders and LEDs from Litchfield Station-the usual disclaimers apply) You will also need a bit of styrene strip-I used Evergreen HO 2x12, which is about 0.025" thick. A Unit Remove the light board, and cut it at the rear of the square hole with the capacitor: Unsolder the front lead of the diode, and cut off the rear lead of the diode, leaving a 1/8" stub-bend it the to the rear. On the bottom of the board cut the traces with a file (this view is from the bottom):

Replace the front portion of the board in the frame, taking care that the motor contacts are on top of the brush caps, not stuck into the side. Cut a length of the styrene strip the width of the board, and tuck it under the rear of the board, securing it to one frame half with a bit of Goo. Check that the motor contacts are not touching the frame and bend/twist them as necessary. Check for isolation with a Multimeter -- there should be no continuity between the frame and the motor contacts, the resistor or the diode lead. Trim off a bit of the shrinkwrap at the rear of the decoder (I trimmed it off at the end of the 'x' in Digitrax) and place the decoder behind the light board with the orange wire to the front right, and secure it with a bit of Scotch tape. The wires are attached as follows: Red-Right front screw Orange-Right rivet Grey-Left rivet White-Diode lead stub Blue-Resistor rear lead Black-Left rear screw Yellow-not used-cut off and tape to decoder. Trim the wires to length and tin the wires that go around the screws. Here's the completed job:

B Unit The B unit is much simpler than the A, as the only trace that needs to be cut is the one on the right between the rivet and the screw. The wires are attached as follows: Red-Right front screw Orange-Right rivet Grey-Left rivet Black-Left rear screw White, Blue and Yellow-not used-cut off and tape to decoder. Here's how it looks: