Making sense of this Circuit

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Thread Starter


Joined Jul 14, 2016
Hi Guys,

I am currently practicing my reverse engineering skills starting at creating a schematic from an existing circuit board.
I have been able to draw the schematic based on a simple led circuit powered from AC. (This is simplified, fuses and discharge resistor gone)

I know the 330nF cap is taking current down to 25mA before rectification.

After this, I am struggling to figure out what the electrolytic cap is doing (smoothing?) and why R1 is there.

I know what a zener diode does and how they work, but not sure what it is needed for here?

If someone could help me understand this I would be ever so grateful. I'm sure something will click with sudden realisation as soon as someone explains.
Thank You in advance :)

Circuit Help-01.png
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