This installation documentation is for the HO Scale MTH SD70ACE. This installation uses the T6XP-LH decoder, and was performed by Thomas Gosser of Alaska.
The picture above shows the locomotive prior to the decoder installation.
Using protected tweezers or other suitable tool you will need to pull the cab attached handrails out of the front of the cab.
Likewise, the handrails will need to be removed from the left and right hand sides of the rear cab. And from the stanchions as indicated by the circles. Place the rails toward the outside of the stanchions for shell removal clearance.
Turning locomotive upside down pry off front and rear truck bottoms as shown.
Using protected tool pull truck side frames off as shown. Be careful as the side frames are connected to wires. Remove each wheel set and set off to the side being aware of gear orientation.
Once the side frames and wheel sets are out of the way we can remove the locomotive shell by prying the indicated tabs out
of the way as indicated by the arrows. The shell will lift off from the top. After the shell has been removed, reinstall the wheel sets and truck side frames. Be sure side frames are fully inserted and parallel to trucks when installing the bottom covers. As the covers snap in place holding it all together.
With locomotive now right side up we see the PCB light board. Remove the NMRA socket jumpers and the number light and ditch light clips on either side of the board.
Plug the harness in. Plug in the decoder so that the Orange wire lines up with Pin #1 of the socket. Pin #1 will be designated with a "1" or a small arrow/chevron. You will need to cut the green wire. Cut as close to the NMRA plug as possible. Strip off some insulation from the green wire as this wire will be connected to the ditch light right (D_R) connector on the PCB.
Strip off some insulation from the brown and lavender wires coming from the T6 Decoder. Connect the wires as shown to the pcb as shown. D_L = ditch light left, NUM = number lights, D_R = ditch light right.
Using Kapton tape start taping wiring harness out of the way as shown.
Use double sided mounting foam tape to mount the decoder as shown. The harness will be taped out of the way, and now the shell can be replaced. After you check installation first! Consult TCS Additional Programming handout for setting up the ditch lights. The number lights can be controlled from F3. Once shell is in place carefully reinstall the hand rails.
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