We published a video in January 2018 describing how to convert an 8-pin Hornby TTS decoder for use in a 21-pin chassis.
In that video, we used a LaisDCC 21 to 8-pin adaptor, customised by removing the 8-pin socket, to allow the decoder to be plugged into a Bachmann Class 47.
While that method is still totally valid and remains the cheapest option (as of today’s prices), we have subsequently discovered a TCS-brand 21-pin breakout board which can be used for the same purpose.
These TCS adaptors are more expensive than the method outlined in our earlier video, but easier to use and require no real preparation. They only come in packs of five, however, and at about £20 per pack, if you only need one, they’re pricey.
We’ll probably do a quick video follow up in due course as we have another TTS chip to convert, but for the time being, as we’ve yet to find any instructions online, here’s a pin-out wiring diagram for the TCS 21-pin adaptor…