As expected, there were many things that went wrong in the process from the prototype to the first PCB version of the project. I would like to share them here, maybe it will prevent similar mistakes in one of your projects.
While drawing the circuit diagram, I copied all values from the components into this document. But later, I experimented with the prototype and changed components – but forgot to update the values in the circuit diagram.
When I soldered the components onto the PCB, I just read the values from the diagram and did not cross check them with the prototype. I soldered the wrong capacitor on the board and it took a while to find the problem. It was hard to remove the wrong component and replace it with the correct one.
How to fix later: If the shape of the components match, you can easily unsolder the wrong component and use the correct one. But often you have to destroy the wrong component to be able to unsolder it.
How to avoid: This is very easy to avoid and there are two safe strategies. First I keep a sheet with the printed circuit diagram beside the prototype. So I can easily note any changes I do and update the diagram later. Second, before I order a new PCB, I check all values in the diagram with the prototype.
Not Connected Copper Pour
I created a copper pour on both sides of the PCB, but somehow I did not connect the pour on the bottom side with
GND. This is not easily visible, because usually while drawing routes you keep your board free from the pours and just add them for the final touches.
How to fix later: You can not fix this entirely, but you can prevent the worst. Just scratch off the solder mask from the largest pours and connect them to ground with a small wire.
How to avoid: If you do the final checks, check each layer individually. So you will spot this problem immediately.