A few days ago I got a mega 2560 r3 ( SainSmart ) which did not work, it was not detected when plugging usb to pc. Although I have very limited knowledge of electronics I tried to detect its failure. I started with a multimeter at least corroborate some volts and continuity observing schematic. Suddenly , when measurements the board was plugged was detected by the computer as UNKNOW (in windows 7). The ends of the tester were between the ends of R2 (in parallel to 16Mhz crystal). Encouraged, I tried to inspect C14 and C15 (22p caps) , I disconnected the board, tested parallel to GND and were ok. I thought it was a problem welding and pressing too took off C14 involuntarily. Despite the accident , I plugged the board and good news ! ( to my surprise ! ) windows recognized the board as " Arduino Mega 2560 " voila!! . Checked (w/capacimeter) C14 and was ok, re-weld it .... but again it stopped working the board ! :~
Anyone know what other defect may be causing this anomaly? Someone knows where I can obtain documents about measures/tests the standard values ??(voltages, continuity, etc.)? Do you think I should do?
I'm afraid to use the board and finish being damaged further.
Thanks in advance! Jorge