This installation documentation is for the N-scale Kato EMD SD40. This installation uses the CN-GP decoder, and was performed by S.K.
Note: Comprehensive information on performing CN-GP installations can be found in our Classic N Installation Guide, and should be read before attempting this installation. More information on adding a rotary beacon to the Kato SD40 can be found here.
Locomotive prior to installation
First, remove the locomotive shell and the factory light boards.
Test fit the CN-GP boards into the frame. As the pictures illustrate, this early-model SD40 needs frame modifications to accept the CN-GP decoder.
After test-fitting the decoder boards and measuring the height of the offending board components, I measured down the frame and I scored guide lines into the metal with the back of an Xacto blade. I made sure to leave generous depth, enough to clear all board components. Once lines were scored into the front and rear of the frame, I broke out the filing tools.
Detail of frame after milling down. Make sure to remove all filings with a stiff brush and use a strong magnet to collect any stragglers before continuing with the installation.
Once the frame has been filed down, test fit the decoder boards again to ensure that they sit in the frame without binding and won't short the frame.
Next, I wired up the decoder. Very detailed step-by-step instructions can be found in the Classic N Installation Guide (linked above). Attach the orange and gray wires to the motor, and yellow, black, and blue wires to the rear board. Be sure to strip and tin the ends of the wires to ensure good contact.
To attach the orange and gray wires to the motor, first trim the top and bottom motor tabs back. Trim the wires to length and solder the gray wire to the top tab and the orange wire to the bottom tab. Make a notch in the casing to allow the orange wire to pass up around the motor and through the top of the frame. Use Kapton tape to isolate the inside of the frame near both motor tabs and wherever the orange wire passes against the frame. Carefully rejoin both halves of the motor and tape the wires into the gap on top of the frame.
To attach the blue, black and yellow wires, first trim the wires to the proper length, strip the ends and tin the wires. Then attach them to the pads in the order shown above. Tape all loose wires down to the top of the frame and give your locomotive a test run. Replace the shell and you're good to go!
Important Soldering Tip
Please do not use any flux either liquid or paste on the mother board. Over time, the acidic properties of liquid or paste flux will begin eating away at the fiberglass PCB and will damage it. Use only Rosin-core solder or no-clean flux approved for electronics use.
TCS recommends the use of Kester "44" Sn63 Pb37, .015" diameter Rosin-core solder. Kester part number 24-6337-0007.
You can order this solder from the following retailers:
Digikey - PN:KE1110-ND
Techni-Tool - PN:488SO6775
Other solder tips
When stripping wire, only strip a tiny little bit of the insulation. Strip no more then a 1/64 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire then half the length of the solder pad at most. In no case should solder or exposed wire wire ever be outside the boundary of the the solder pad you are attaching a wire to.
Click here for important information on properly Stripping and Tinning wire