I do not know why this is happening because the circuit is literally just some LEDs and resistors, so I assume it is a problem with the power supply. It comes with a stock 10.7V power supply, so I tried swapping it for my 12V 2A power supply from my Seagate hard drive and I obtain similar results. Should I rewire the LEDs somehow to make this problem go away?
You see on the back of the lamp how towards the middle of the PCB the colour changes to a more brownish/yellowish green?
That's caused by excessive heat.
You will probably find, on closer inspection, that the side of the SMD resistors closest to that heat have become detached from the PCB. Use your soldering iron to refresh the solder joints, and you may well cure the problem ... for now.
It may not be visible to the naked eye, especially when the lamp is off. What is probably happening is that the heat from the lamp is causing parts to expand, which is breaking the joints, which is turning off the LEDs, which is letting the parts cool down, which is fixing the joints, which is turning the LEDs on, which is heating up the parts, which is ... flicker flicker.
Wow, I never thought that the heat would actually affect such a simple circuit, but I guess it does. Here are some more close up images. I found that under each resistor there is some kind of red buildup. I am assuming that isn't good. The LEDs also glow the PCB red with both power adapters.
The problem circuits are resistors 1, 7, and 5. I tried touching the solder joints on the center pad with a wire but it doesn't do anything, so I will have to wait until I get access to a soldering iron. Then I'll refresh the joints and try replacing the resistors.
I did a multimeter test too and it appears that the LEDs closest to the center have voltage drops of 5V (flicker) and 6V (this branch does light up at all). I think the LEDs are overheating. Is there a way to solve this? Maybe drive at a higher voltage at 75% duty?
The red "buildup" could well be just a glue used to stick the resistors down while hand soldering. I haven't ever seen anything other than smoke come out of a resistor.
Running at a higher voltage with a reduced duty cycle will be no different, as the total average power will stay the same. The usual way of combating heat is to move the heat away somewhere else through the use of a heatsink. There doesn't appear to be any form of mounting for a heatsink though on that PCB, so they probably never expected to need one.
I have this same issue! Except only with one bank of 3 LEDs. My temporary compromise is dropping the two end LEDs to cut out that bank all the way across (for even lighting). I know this post is old but did you find a solution for this?
