EDITED to update diode spec and schematic...
I have two failed outside security lights each with PIR circuit with relay to switch 240V AC mains voltage to another circuit which looks to be a simple AC/DC converter which then feeds a matrix of 60 LEDs wired in series.
Looking at the (very) simple circuit board, the AC/DC converter looks like the image below...
Apologies, the image isn't great. List of components...
L1 4.0 is all it says on the side. Just a radial inductor. R1 510K (1/4W by the look of it) C1 0.68uF metallized film
U1 4x 1N4007 diodes arranged as a bridge rectifier
C2 4.7uF 400V axial electrolytic R2 15R (also possibly 1/4W)
OK, so R3 is unknown as it has been fried and the outer resin coating along with colour coded bands has turned to dust (the PCB also has a nice blackened look to it). Interestingly though, the resistor is still mostly intact and my meter reads it as 54K but I don't know if that was its original value or if it has degraded due to partial burn-out.
So, what's my question? I've wired the input directly to the mains and left the LED matrix in place. I measure 239V AC input (close enough) but I'm seeing 292V DC on the output. How is that possible?
The LEDs don't light up but I've since worked out that's because one of the LEDs has blown (all others test OK).
I'm assuming that R3 is under-rated and should be at least 1W if not 2W but even at that rating, what should its value be based on the general design (54K?, something else).
I've dealt with this sort of circuit before but normally with input fed from the secondary of a 12V transformer (for example) and output going to a voltage regulator to create a regulated PSU. I've never dealt with a straight 240V AC-DC converter before.