How to convert N Gauge Graham Farish Class 158 (Split Chassis) to DCC

This guide covers the following models:

• Class 158 DMU in Northern Rail livery (371-556)

China Split Chassis Conversion

The conversion requires part of the chassis milling away to isolate the motor from the track power. Some split chassis arrangements also require some of the top milling out to make room for the decoder.

Step 1 - Remove body

Remove the body by gently pulling upwards. Also remove the underfloor box.

Step 2 - Split the chassis in two

Unscrew the screws holding the capacitor between the two halves of the chassis. Unscrew both screws holding the halves together. They screw into plastic nuts.

Gently prise the two pieces apart, and carefully remove the two bogies and the drive shafts. Don't loose the plastic spacers as they are very important!

Step 3 - Prepare the motor

Remove the motor. Notice the way that the copper contacts on the motor touch the respective sides of the metal chassis. Power is conducted from the wheel pickups to the motor this way. With the motor out, solder a grey wire to one of the contacts and an orange wire to the other.

Step 4 - Remove part of the chassis

Using a Dremmel or a file, remove the part of chassis that was previously contacting the motor. This enables us to insert a DCC decoder between the track power pickup and the motor. Here you can see the area to remove before, and after.

Step 5 - Put the chassis back together

Refit the motor, being careful to check that there is no possibility that the chassis can touch the motor contacts where you previously soldered the grey and orange wires.

File away the black coating from where one of the screws will meet the chassis. As you put the two halves back together, trap a red and black wire at either side so they make an electrical contact with the chassis. These will become our track power feeds to the DCC decoder.

Step 6 - Fit decoder

The decoder will not fit inside the body unless you remove some of the plastic from the inside roof area. An alternative to doing this, is fitting the decoder inside the underfloor accessory box.

Step 7 - Test

Put the DMU on your test track and read the loco ID. It should shuffle backwards and forwards, and then return the default loco ID of 3.