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Installing a DCC decoder in a Bachmann Class 66 (early version with 8-pin socket)

This page was last updated 29 March, 2020

Click on each image for a more detailed view.

Last updated 29 March, 2020
Class 66

Before installing chip into any loco it is advisable to check the current being drawn by the loco. You should test the current drawn when the loco is stalled to find the peak current and select a decoder that will cope with that maximum current requirement.

A TCS MC6 decoder (no longer available) was used in this particular installation.

Removing the body should be straightforward but do not get caught out by expecting the securing screws (of which there are four) to drop out. They don't! The screws should be undone gently until you can tell they have reached their maximum release position (by hearing a slight clicking noise as the screw goes round). The body is a very tight fit to the chassis, so once the screws have been released it is a question of gently levering the body away from the chassis, rocking it gently one end at a time.

Bachmann 66 circcuit board
There are a lot of wires inside the Bachmann 66 from the circuit board, most of which are held in place by sticky tape at each end. This tape will need to be cut to release the wires. There are two screws holding the circuit board in place at diagonal corners. Undo these screws to release the circuit board.
Bachmann 66 circuit board

Installing a decoder in this loco is really very straightforward. Gently remove the dummy PCB in the NMRA socket by levering it out from each end with a flat screwdriver.

One notable weakness is the soldering of the wires to the LEDs from the circuit board. Make sure these wires do not become detached or you will have to do some resoldering.

Bachmann 66 NMRA socket

Once the existing PCB has been removed it is obvious which way round the new NMRA board should plug into the socket as pin 1 is labelled clearly on the underlying PCB.


Bachmann 66 capacitors

With the circuit board released from the chassis and the wires released by undoing the sticky tape at each end of the loco, gently lift the circuit board. This will reveal 2 capacitors which MUST BE REMOVED in order to allow this particular decoder to run efficiently. If they are not removed performance of the loco will be at least jerky and have little control over slow running, to having a runaway at worst. The new type of TCS decoders with back EMF may allow the loco to run without removing the capacitors.

Relocate the circuit board and fix with the screws. Fix the decoder to the chassis using an insulating "Sticky Fixer" double sided adhesive pad. Test the decoder in the loco and set it before replacing the body.

Details will follow on how to use this decoder to make more effective use of the day/night settings and program the use of individual lights.


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