I wanted to test one of the Lego motors without setting up the whole kit.
The motor is designed for 4V DC.
Dug through my bin of random wall warts. Closest I could find is 5V DC
(and 0.5A but I'm not sure if that matters).
Snipped off the wart's barrel connector, spliced a mini-banana lead to
each wire, and the motor happily spun away.
When I tested the Lego computer interface port voltage it showed around
3.7x on my multimeter whereas the wart produces 5 true.
Will I cause any long-term damage to the 30-year-old Lego motor by
running it at 25% higher voltage than intended? Is there anything printed on the motor to indicate intended input voltage? The components between where the supply connects to the box and the output port to the robot regulate the voltage down before it gets to the motor based on your readings. So, any burning out of components will occur in the "box " not the motor. Short term probably not enough to be a problem. 4v is less likely to be in a parts bin but I am sure a correctly-rated power supply is easy enough to find, I'd get one if you can because a too - hot supply will eventually burn out whatever is regulating the juice down before it gets to the motor. Bil