Reverse engineering of a mains power controller.

Test and investigation of a phase angle control motor speed controller from China.
There are two components on this PCB that cost me MORE to buy individually than the entire cost of this assembled unit including shipping!
It's a very standard phase angle control module for varying the duty of mains powered devices like lamps, transformers or some motors (mainly universal motors).
The circuit does have basic suppression, but lacks the important choke that prevents strong radio interference, especially on older AM radios.
Other than that it's a nicely built module using a textbook design and a beefy triac on a chunky heatsink. They claim it's rated for up to 2kW, but I'd be wary of using it on anything near 1kW continuously.
Note that the triac used has an isolated tab but that's not always guaranteed, so the heatsink should be regarded as being at mains voltage, as should the whole PCB. If the module is mounted on a metal panel (using the potentiometer nut) then the panel should be grounded/earthed for safety.