Bachmann GP35

Scale:
HO Scale


This installation uses the following decoder:

M1



The installation is for HO Scale Bachmann GP35. It uses M1 digital decoder and was performed by A.G.

The two upper pictures show the beautiful Bachmann GP35 with its shell on prior the TCS M1 decoder installation. This installation is rather involving due to the fact that the locomotive chassis is not isolated from the motor. Simply follow the step-by-step write up and you should be good. We do not recommend this installation for a beginner.
Remove the two phillips screws marked in red and remove the plastic fuel tank cover.
The picture above illustrates the plastic fuel tank cover removed.
Remove two phillips screws that hold the chassis and the together.
Here is a picture of the locomotive with its shell removed where you can see the original light board.
Remove two phillips screws (marked in red) that hold the original light board and chassis together. Be careful not to damaged wires.
De-solder both motor wires (green and orange) and forward light leads.
De-solder reverse headlight.
Gently remove the original light board and both lights (forward and reverse) as shown in the picture above.
Because of the fact that that motor is not isolated from the chassis we have to take it completely apart. Remove all 4 phillips screws (marked in red) being careful not to loose plastic spacers.
Gently remove front and rear couplers as shown in the picture above.
Gently remove the right side of the chassis exactly as shown above.
Bachmann uses resistors and capacitors in their motor circuit that are not needed for DCC operation and might affect decoder's slow speed performance. Remove capacitors and resistors by either clipping them off or de-soldering them.
Remove the motor from the chassis.
Here is a close-up picture of the motor where you can see capacitor and resistors removed.
Solder the green and Orange wires to the exact motor tabs as shown in the picture above. Isolate the connection points.
Gently, place the motor back to the chassis.
Use Kapton tape to isolate any exposed, electrical connections.
Put the both chassis halves back together reversing the steps you did before. Be careful not to pinch any wires that would potentially caused short and damage the decoder.
TCS M1 decoder was the best choice to use in this installation due to the space limits. Black, electrical tape was used to fix the decoder to the chassis. The picture above also shows the orange wire of the decoder being soldered to the orange motor wire. I used red shrink tube to isolate the connection.
The picture above shows the gray decoder wire being soldered to the green motor wire of the locomotive.
Next step was to solder both (front and rear) red power pick-up wires and red decoder wire together. The same analogy needs to be repeated for the black power pick-up wires - solder both black power pick-up wires and the black decoder wire together and isolate the connection.
The locomotive uses 12V Bulbs so we do not need to use any resistors. The picture above represents reverse light. One side of the bulb (it does not matter which one because bulbs are not directional) is connected to the yellow wire of the decoder, and the other side of the bulb is being connected to the common blue wire of the decoder.
Here is the close-up of the forward light - white wire is solder to the one side of the bulb and the other side will get the common blue wire from the decoder.
Here is the picture of a finished TCS M1 Decoder installation. Black electrical tape was used to fix all wires to the chassis.

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 than a 1/32 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire than 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