[allan]

I fell asleep a few times through that video... funny.. but when he spotted the new diode he mentioned the lack of a resistor.
Those pyrotechnics inside the last 3S4 reminds me of commissioning a new computer rack in the early 70s. It was assembled at the Plessey Poole factory and delivered to the Plessey Liverpool factory for commissioning. Someone had wired a set of flash bulbs across the mains input switch before it left and you can imagine what happened when the engineers turned it on.
Allan G3PIY