DigitalRooster Mk3a

Check Your Silkscreen!

Finally I received the assembly for the revised layout of my Audio PCB. Covid-19 has affected lead times but PCBway was quicker than estimated. Unfortunately not everything was working and it is not pcbway’s fault. I learned you should not blindly trust the CAD data you get, even from ultralibrarian.

I have ordered a new batch of five prototypes of the latest revision of Digitalrooster-Audio Mk3A. The idea was this would be the final prototype before ordering a small batch to sell on This time pcbway assembled most parts manually. They claim they placed and soldered the ICs on the machine but I have my doubts. It makes little sense to me to create a stencil, program the pick-and-place, put 5 PCBs on a SMT line,mount five chips each PCB, go through reflow and later hand-assemble the 40+ resistors and capacitors…. But I am no expert on SMT production. Anyway the super-cap was inverted on the proving pictures they sent, I checked and asked for correction, easy.

I missed the to check the orientation of U1, the LED driver TLC59208F, it was turned 180°. This is not pcbway’s fault. I also probably would not have caught the error. Look at this silkscreen! See where the marking is? Clearly not next to pin 1.

PCB layout view of chip footprint with silkscreen

I got the TLC590208F CAD data from and didn’t event think about the possibility that this could be an issue - I was wrong.

Connecting the PCB to Raspberry Pi short-circuited the 3v3 rail and probably killed the touch controller of one of my displays. But the bug was easy to find the chip got really hot, I almost burnt my fingers. Asking around among my friends, nobody had a hot-air desolder station available. The way to remove the chip was using a common hot-air blower, wrapping the PCB in Aluminium foil. This worked pretty well. Soldering the chip was not that easy for my shaky hands and big solder tip. I had three new chips left, two have been soldered successfully.

In the end I am happy finally I have backlight control PWM on a Banana Pi. I will fix the silkscreen and make some minor layout improvements in KiCad. Some smaller points like matching the APDS9960 connector to match the Adafruit APDS 9960 breakout board and beautification.