This installation is for a HO-Scale Walthers Proto 1000 R21 Subway Car using a TCS T4X Decoder and was performed by TCS.

Important Soldering Tip:
Please do not use any flux either liquid or paste on the mother board. It will damage it. Use only Rosin core solder approved for electronics use.
We recommend to use only Kester "44" rosin core, SN63PB37, .015" diameter, part number 24-6337-0007.
This can be ordered from Techni-Tool under Techni-Tool part number 488SO157

HO-Scale Walthers Proto 1000 R21 Subway Car prior to T4X decoder installation

HO-Scale Walthers Proto 1000 R21 Subway Car prior to T4X decoder installation

In order to gain access to the factory light board for the T4X decoder install, first remove the four screws securing the car shell to the chassis.

One set of screws is marked with the red circles in the above picture. Once the screws are removed, carefully lift the shell off of the cars chassis.

With the shell now removed, we now have access to the facotry light board. Located on the left side of the factory light board is the 8-pin plug for our decoder.

Highlighted above with the red rectangle is the 8-pin plug and jumper. We can remove the jumper at this time. Next, remove the two screws securing the factory light board to the motor housing.

With the screws removed, flip the light board over to gain access to the interior light bulbs (total of 2).

Since the traces these bulbs are tied into are track pick-ups, we must remove the bulb in order to be able to have control over them via the decoder.

First, desolder both leads of the bulb marked with the red circles in the above picture. Do this for the second bulb as well.

Note: The leads to these bulbs are delicate and can't be flexed too much.

With the bulbs removed, we can now solder our wire leads on.

In this install we are using function one to control the interior lights. This means we are using a green wire for our function output, while the blue is the common plus.

Cut about a 5"-6" piece of wire for each lead. Make sure to insulate your solder connections with 1/16" shrink tubing.

Now that the bulbs have leads, we can now mount them back on the underside of the facotry light board. We used some medium CA glue for quick and easy adhesion.

With the bulbs wired and adhered, we can now reattach the factory light board to the motor housing using the two screws we removed earlier.


With the factory light board mounted, plug in your T4X decoder. The T4X comes with a standard hardwire T Series harness. For ease of install we used a T1" harness.

Next, we must wire our interior lights to the decoder. Marked with the red circles in the picture above are the function (green) and common plus (blue) wire connections.

With all our wire connections made, we can now neaten up our install. We used some kapton tape to clean up the wiring

and double sided foam tape to secure the decoder to the factory light board.

Finally, reattach the subway cars shell and reinstall the four screws.

You have now installed a TCS T4X decoder into your HO-Scale Walthers Proto 1000 R21 Subway Car.

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

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