[Adrianxpress]

Hi, I have a remote-controlled toy train. The remote is 27.145 MHz and uses a 9 volt battery.
The remote has three buttons. Pressing the top button makes the train goes forward. Pressing
the bottom button makes the train go backwards and pressing the middle button stops the train.
You cannot control the speed at which the train operates.

Is it possible to attach a speed controller to this device that can be done in a relatively easy and economical way?

 

[Martaine2005]

27.145 MHz is channel 4 or YELLOW for RC cars, boats etc.
It’s now old technology.
But to answer your question, it’s definitely possible and reasonably cheap to do so. You will have to disassemble the train.
This will most likely involve replacing all the electronics in the train for a digital proportional RC handset and servos.
These can easily be found on auction sites.
But for the time being, can you take some photos of the electronics in the train and upload them here?.