I recently bought A20-SOM-EVB. Now looking at the third small picture on https://www.olimex.com/Products/SOM/A20/A20-SOM-EVB/open-source-hardware (https://www.olimex.com/Products/SOM/A20/A20-SOM-EVB/open-source-hardware), there is a noticeable, black, cylindric part on the back of the board near the SD card slot. The board I got (Rev.C) does not have this part. Is it still safe to use my board or is there some defect with it? Thanks in advance.
That's an electrolytic capacitor and without knowing where it is connected to, is hard to determine why it is needed. Looks like an afterthought where there is some issue with one of the power rails dipping.