You wrote the capacitor code incorrectly on your schematic. 684 is 680nF.
It isn't unusual for capacitors designed to operate off AC to be marked with the RMS voltage rating, another possibility is it's just junk and they've undersized the parts.
Where did you get this circuit board from? It's not very good quality.
There should also be a zener diode or other kind of shunt regulator in parallel with the 1000µF capacitor, otherwise the voltage will exceed its maximum rating, causing it to explode.