Technical

Greetings fellow members. I have a problem where the red wire from the PCB board connects to the top side of the servo motor just in front of the heat block. The red wire ends with a ring type connector through which a small shiny metal cylindrical part together with a very, very tiny spring locate into the hole on the top of the motor, supplying power to the motor. This connection has always been a bit loose but has now come out completely. On attempting to relocate this cylindrical part and spring I can't work out how it is secured in the hole as it doesn't seem to fit over anything to secure it - perhaps a missing part. Has any one experienced a similar issue? the problem has rendered the loco inoperable so any guidance would be greatly appreciated.