Re: MiniPOV 4 problems
by bodger on Wed Nov 16, 2016 12:10 am
I just put together my MiniPOV 4, and two of the LEDs work fine for red and blue, but not green. I thought about it for a while, and since the LEDs light, that tells me that their I/O pins and current limiting resistors are OK, and since the others work for green, that tells me the I/O pin, transistor, and base resistor for green is OK as well. That leaves a problem in the PCB trace, a bad solder joint, or two LEDs that don't work right. The datasheet doesn't make it clear which pin is green, so I pulled up the board design in EAGLE, but that signal isn't named. I went to the schematic and named the red, blue, and green LED drive signals, then was able to match them with pins on the board view, so I know which pin is green. I measured with a continuity tester, and the pins are connected to the other green pins. I also tried probing those pins with an oscilloscope with the unit running (up high near the LED, not just down at the solder joint), and they show the same signal as the other LEDs. Therefore I think the problem is with those two LEDs. I really don't think I overheated them while soldering. I did try reheating those joints just in case, but that didn't cause improvement.