Minitrix Class 27 DCC Conversion

Mistakes may damage your locomotive, controller or other accessories. Use a multimeter to make absolutely sure you have completely isolated the motor from the track before testing. Always use the Programming Track for testing. Our guides are provided for reference only, and you proceed entirely at your own risk. Unsure about something - try our DCC Conversion Service instead.

Buy Minitrix Class 27 DCC Conversion for £50.00

This guide covers the Minitrix Class 27 models, including:

• N205 Class 27 D5379 (British Rail Green)
• N212 Class 27 27014 (British Rail Blue)

Step 1 - Remove Body

Remove the two screws in the roof of the body and then gently lift upwards away from the chassis.

Step 2 - Modify Upper PCB

Remove the upper PCB. Remove the screws holding the motor bracket in place, and take out the motor.

Take the upper PCB, and desolder the two wires coming from the lower PCB. Remove both resistors - these are not needed for DCC operation, so can be discarded. Also remove the copper tabs that push against the back of the bulbs. Solder a blue link wire to connect the tracks as shown, this will provide us with a neat common positive 'rail' to connect the tip of each bulb to later. If you are replacing the stock bulbs with LEDs then use the alternative wiring diagram that includes a 1k Ohm resistor between the decoder and the common positive.

Wiring Diagram for Filament Bulbs / No Resistor

Wiring Diagram for Filament Bulbs / With Resistor

Cut a small notch out of the side of the PCB to provide a way to route the wires from below the motor to the top side of the PCB.

Step 3 - Modify Lower PCB

Take the lower PCB, and remove the capacitor and choke. Desolder the two copper tabs that touch the motor contacts, but leave the one that touches the chassis.

Solder the red decoder wire to the centre strip of the PCB. Solder the black wire to the remaining copper contact. Route the wires through and towards the top side, then replace it back into the chassis.

Step 4 - Connect Motor

Solder a grey and orange wire directly to the motor contacts.

Route the four wires up through the gap and re-seat the motor. At this point, it is a good idea to check that the track pickups are completely isolated from the motor wires using a multimeter. There should be no continuity between red/black and orange/grey.

Step 5 - Modify Lighting

Remove the clips that go over the top of each bulb. Remove the bulbs.

Solder a blue wire (common lighting positive) to the tip contact of each bulb. Solder a white wire to the outer casing of one bulb, and a yellow wire to the other. Add shrink sleeve around the outside so nothing can come into contact with the metal chassis.

Refit both bulbs. Route the two wires from each back up through the holes left by removing the bulb tip contacts to the top side of the PCB. Solder the blue wire from each bulb to the PCB as shown in the diagram above.

Step 6 - Connect Decoder

Fix the decoder to the top of the upper PCB using a sticky pad, black tack or kapton tape. Make sure the decoder and wires are routed well clear of the holes where the body screws go.

Solder the red, black, grey and orange wires to the decoder. Connect the front and rear (white/yellow) lights and finally the blue common positive(s). If your decoder does not provide a common positive, you can usually use one of the track pickups instead - but check your decoder manual first.

Step 7 - Test

Put the loco on your programming track and check that you can read the loco ID. If all is well, refit the body and the conversion is complete. Depending on the decoder you have used, and your preferences, you may want to dim the lights a little as the default decoder setting can make them very bright. Sending too much power to the lights can also burn them out. Consult your decoder manual for which CVV values change the brightness.

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