Hackaday · Creativity & design

Repairing a Vintage LEGO Electric Train Speed Regulator

A 1990s LEGO electric train speed regulator (model 2868b) was recently repaired, showcasing older electronic design principles.

The regulator used metal rails to power and control the train's speed and direction via an external power adapter. Inside, a single PCB featured a variable voltage regulator controlled by resistors, which the yellow switches altered to change output voltage and polarity.

The only active component on the board was a Fairchild KA317 voltage regulator, similar to an LM317T, mounted on a heatsink. Replacing this component restored the regulator to working order.

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