UFO (undentified flat object)

[(*steve*)]

How do I measure + calculate their optimum voltage levels? (I don't have an oscilloscope but would that be the best way, alongside a very accurate adjustable voltage source?).

I would suggest you look at the original board which seemed to have series resistors for each colour.

If that board runs from 5V then determining the max current that they were run from is a simple calculation. (Yes, you will have to measure Vf to do the calculation). Another way is to connect the appropriate resistor, and measure the current when operated from the appropriate voltage supply.

 

[NuLED]

ok thanks Steve. that should work. I still have the PCB and can measure the Vf across the SMD resistors. But I would have to make the assumption of 5V as the supply voltage (not a wild guess, since the thing is a USB hub). I will try to trace where the DC jack goes (it has that to allow powering the USB hub, my guess).