It only took me one year to finish the version from the previous log. Of course I assembled it as soon as the PCBs arrived, but I couldn't get it to work, and I blamed bad soldering on the LEDs, which unfortunately couldn't be easily corrected, as they have SMD footprints, and for practical reason of being arranged in a tight display, there is nothing sticking out.

After several attempts at getting it to work using my mini-hot plate, I mostly gave up on this.

A few days ago I went and tried to assemble a second PCB, this time using a more common LED footprint, that could be soldered by hand and easily reworked. And of course it didn't work either. So I desoldered all but one LEDs, and started investigating, and turns out this whole time I had the rows and columns switched. Duh.

So I went back to the original unit, switched the rows and columns, and what do you know, it worked, with only a few "bad pixels" due to soldering. But those were easy enough to fix using the hot plate, so now I have a fully working unit. I might also finish the second one with regular LEDs, but soldering them by hand is a bit of a chore, so we will see.