The layout seems to be, after measuring with multimeter:
DTR# - C4 - RESET - R9 - VCC(ICSP)
C4 is an unmarked, beige capacitor. R9 is marked '103'.
So to me that looks like a pull-up meant to keep RESET high unless DTR# actively drops it to ground, yeah?
I have a capacitance meter, but I doubt that would be much use while the capacitor is still on the board?
...and I just noticed that on the PCB they've misspelled 'COMMUNCIATION' for pins 14-21. Heh. Quality!
You can measure R9 to verify its value. Sounds like C4 is shonky (numbers might be on other side!).
R9 measures to 10kOhm. Also, all capacitors on the whole board are unmarked beige. I suppose that they could have fed the tray upside down.. somehow.. so that every one of them end up wrong side up.
The beige caps are usually 0.1uF (100nF).
Once they get down to a certain size marking becomes too hard to read.
You can see the color difference between the 0.1uF here and the 22pF next to the crystal here on these 0805 size caps.
CrossRoads:
The beige caps are usually 0.1µF (100nF).
And there's the point.
The combination of 0.1 µF and 10k works in all common UNOs and mega2560s, so if it is what he has, why then is it not working?
I suspect 10 nF caps are beige too.
Here's a picture of the relevant area of my Mega board.
C4 and R9 are clearly visible, and you can see the '103' writing on R9. As for C4, it looks pretty much the same as the other capacitors.
Buongiorno,
io avevo lo stesso problema, e dopo aver sostituito C4 da 0.1uF-SMD con uno da 10uF-16V cilindrico verticale il Mega 2560 ha preso a caricare i programmi perfettamente...
vai a sapere...
NIK
I just want to point out that here in 2018 this is combination of things causing this issue is still showing up. Had a 3D Printer (MKS Gen L) board have this exact issue. Resolving with making a 15K Ohm Jumper for the ICSP pins 5 & 6. Will probably put it on when programming and leave it off otherwise but at any rate sufficiently worked around.
I ended up replacing the 0.1uf cap just to make sure I knew it was the correct version, and I found the pull up resistor was actually 10k as well.. so, the components were normal as this thread had also concluded.
Sorry for bringing up the dead thread but really just wanted to back up this conclusion here in 2018 as well
