Inside a "4kW" ebay power controller with schematic.

This is a look at another Chinese industrial control component.
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At first glance this phase angle power controller has a strong case resemblance to the common 12V chassis power supplies. But this is a beefy triac based mains power controller for things like lamps, heaters or some motors.
It has a few notable features:-
Nice case, beefy triac (one of the biggest of its type if it's original), extra circuitry to give greater stability and output symmetry at lower levels and a bit of effort to ensure that tracks are robust enough to handle fault conditions.
It does have two slight issues. A glass fuse instead of a ceramic one and a seemingly excessive resistor value in the snubber network. 4700 ohms as opposed tot he more common 100 or even 47 ohms.