How to convert Bachmann OO Gauge A4 (Sound) to DCC Sound

This guide covers Bachmann A4 OO gauge split chassis steam models, for example:

• Bachmann Class A4 4489 'Dominion of Canada' in blue (31-950)
• Bachmann Class A4 60011 'Empire of India' in BR Green (31-950A)
• Bachmann Class A4 60009 'Union of South Africa' in BR Green livery (31-951)
• Bachmann Class A4 4903 'Peregrine' in blue livery (31-952)
• Bachmann Class A4 4468 'Mallard' in blue livery (31-952)

It may also be suitable for other similar models. The procedure is broadly the same as for other Bachmann OO Gauge steam locos with the split chassis arrangement.

Step 1 - Disassemble Loco

Undo the two screws underneath the loco and lift off the body. Remove the two baseplate screws, and remove the baseplate. Gently remove the plastic conrod guides - they are fragile and break easily. Later models have a metal piece instead here, which is much better. Drop out all three sets of wheels.

Picture shown here is from a Royal Scott.

Step 2 - Modify Chassis

Remove the screws holding and separate the two chassis halves. Remove the motor and the two contact springs.

Solder two black wires to the motor contacts and add some heat shrink sleeving. Refit the motor, reassemble the chassis halves, then refit the wheels and base plate.

Pictures shown here are from a Royal Scott.

Step 3 - Add Track Pickups

Solder two black wires to the copper tabs at the rear of the chassis. Solder the dolly wheel contact wires back on too, if you removed them earlier to make it easier to disassemble the chassis halves.

Step 4 - Reassemble Loco

Drill a hole through the cab and pass the four wires through. Refit the loco body and screw the two screws back in underneath.

Step 5 - Modify Tender

Remove the base plate and drop the wheels out. Remove the other two screws, then lift off the tender body.

Drill a hole in the tender body and pass the four wires through.

Fix the decoder to the inside of the tender body, using black tack or glue. Make sure the decoder is protected from shorts using kapton tape.

Step 6 - Fit Stayalive

This is an optional step, but really improves reliability and prevents sound drop-outs over poor bits of track. Here we are using a Train-o-Matic Power Pack which works well with ESU LokSound 5 decoders.

Glue the stayalive unit in place at the front of the tender, making sure it cannot make electrical contact with the metal weight. Train-o-Matic stayalives come already inside heat shrink sleeving.

Solder the three stayalive wires to the decoder.

Step 7 - Fit Decoder Socket

Glue a piece of plasticard to the metal weight, in the middle between where the two support pillars pass through. Glue the 8-pin socket to the plasticard.

Solder the four wires to the socket.

Step 8 - Fit Speaker

Here we are using a large YouChoos Breeze speaker. Glue it in position, then solder the two speaker wires to the decoder.

Plug the 8-pin decoder into the socket.

Step 9 - Refit Tender Body

Refit the tender body. Replace the wheels and base plate, then hook the tender back up to the loco.

Step 10 - Test

Place the loco on your programming track. Test that everything works correctly and the conversion is complete.