Ah, thanks for that, Eric
"Interestingly" (as in, interesting, but I know there are those who will say it's not strictly coffee) since I originally posted those thoughts, I've been playing with the circuitry in my "P" model hottop. I figured it would be useful to have a proper handle on the differences between these newer boards and the original ones.
Anyway, what I believe I discovered recently, with pretty much 100% certainty, is that my "P" model hottop does not and cannot use Phase Angle control ! It can only use Phase Width Modulation which is synced with the AC mains zero cross for maximum possible accuracy for that method.
The post on HB seems to imply that there's a difference either between "P" and "B" or US / UK hottops that would explain the different findings. I've posted my comments there to see what comes back. I'm pretty sure I was told the internal boards were identical for "P" and "B".
As zix pointed out earlier, PAM / Phase control can generate electrical interference from the switching, so perhaps EU regs are stricter on this ?
Swapping one chip on the internal board would allow my model to do Phase Control, but I'm not convinced any potential greater control that might come with this outweighs the possibility for interference, when given PWM that is accurately locked to the mains cycle, so you can eg. run 100ms PWM periods to get 10% granularity heater control (n out of 10 mains half-cycles)
While I'm posting on obvious differences between the models, I discovered that on the "P" model at least, when compared with the original hottop electronics, the connections run the opposite way on the connector, and require driving to 0v to activate their functions, not 5v like the old one.
Oh, and I also discovered exactly how much interference is generated inside a hottop when I looked at all the signal crap coming out of my thermocouple. Hats off to Fluke, their 51II can really filter a signal to give a clean temperature reading, especially when compared with what the raw signal looks like on a 'scope. The highlight was turning on the hottop's drum motor, and seeing my own temperature readings plummet by something like 18 degC due to induced voltages on the thermocouple...