Thomas goes digital

[Cliff George]

The loco as delivered has a small circuit board on the back of the motor

Yes

and another one to which the motor and pickups are connected.

I don't beileve my Thomas had another circuit board, just the one on the back of the motor. I think later models were fitted with an NMRA reversing switch and may have been the cause of the extra circuit board. My 'James' did have two circuit boards one on the the motor and the second for the reversing switch and in that case I removed the reversing switch but retained the board with the interference surpression capacitors.

I'd normally just bypass all onboard circuitry and connect the decoder directly to the pickups and motor, but looking at the pictures above it would seem that the board on the back of the motor has been retained while the other has been removed. Is that correct? I'd just like to check what has worked for everyone else.

As ntpntpntp says, you could take the board off of the motor, but for some reason I can't remember I decided to retain it (possibly I thought it was easier to solder too). I don't think it is causing any problem with slow speed running. If it had have done then I could have taken it off later.

 

[jimmielx]

My Thomas does indeed have a reversing switch. I'll leave the board on the back of the motor and bypass the other as suggested.

Many thanks for the replies chaps, much appreciated.

 

[mikesilky]

Apologies for dragging up this old thread, but it appears pretty high up in Google when you search for terms relating to "G Scale" "Thomas" and "Decoder", and this post might save people some time and a lot of swearing.

To get inside Thomas to fit a decoder, you only need to remove the rear-most six screws from the underside of the footplate. You can then remove the majority of the body - cab and most of the boiler. It lifts off upwards in one piece.

There is no need to remove the front two screws, which hold in place the black part of the boiler and face. I really would avoid doing this, because getting the moving eyes back in place correctly is an absolute pain in the backside.