I have a Christmas Thomas engine where the receiving board (older, not Bluetooth) no longer works. Would cost more than $55 for a new board with shipping. Not worth it. Is there an easy way to bypass the board and just run conventional? Not even sure if the motor is AC or DC on these things.
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Assuming a DC motor, commonly a full bridge rectifier is used. You can add a DPDT switch to change direction by swapping the leads to the motor.
In general, it looks like this: 
or with switch:
Do this "all the time" for our Thomas type locomotives on our display layout at our local club when something goes wrong with the electronics. For a part that is less than a dollar we get a reliable locomotive that suits our needs perfectly. It only goes forward but that is perfect for kids. An easy installation. Only takes me a few minutes.
Thanks. I am not afraid to do this sort of thing, but I am not an electrical expert. What full bridge rectifier should I use? If I understand the diagram correctly, the two wires from the motor are soldered to two leads on the rectifier (which two?), and two other wires are soldered to two other leads that go to the pickup and something else? A picture of the actual wiring for this would help, if you have one handy.
It depends upon the rectifier, but the typical one will have 4 leads - two are marked "~" for AC input. One of those goes to the center roller pickup, the other the metal frame of the locomotive. The other two leads on the rectifier are marked "+" and "-". These go to the motor.
The TS4K40-A or KBP307 are reasonable choices out of the many many many that are out there. I have an excess of the latter and can send one out to you, no charge (my contact email is in my profile where it is only visible to members like you).
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