Talking to me a decade on, now with 8-bit experience!

Thirteen years ago I posted this snippet of text from Wikipedia, and joked that it must be how it feels to talk with me when it comes to my more esoteric interests: The GTO thyristor used on 1996 stock achieves this by “chopping” the supply voltage in order to drive a sinusoidal current in the motor windings (pulse width modulation), creating the characteristic audible whine associated with the stock and with the Class 465 Networker trains that share its traction drive system. The sound changes as the pulse length changes. The noise is produced by the switching frequency current ripple and the resulting torque pulsation experienced by the rotor of the induction machine. I had no idea what most of this meant at the time, but re-reading it now, I do! I have no formal electrical engineering education (I’m a biscuit), and hadn’t touched a soldering iron until my 30s. But repairing 8-bit machines and using (abusing?) oscilloscopes for troubleshooting have been great teachers. I had no idea…