Hi forum,
I've just finished soldering my "Make Your UNO" board. However, when I'm connecting it to my PC via USB-C, only the Green LED is turning on. I can notice a very dim and short blink on LD4 while plugging or unplugging the USB cable. What could have gone wrong? How can I debug my Arduino? Please help!!!
I see what are likely cold solder joints. Example
Show the obverse side (this from the Arduino.cc web site).
... and dull solder shows overheating. Apply flux to every solder joint. Heat until solder just turns fluid. Brush clean with isopropyl alcohol. You should see shiny peaks.
Contact Arduino Tech Support via Contact us. Give full details of the issue.
Here's the top side of the UNO.
Shall I just go over all the pins with a solder or I need to unsolder them all and start from scratch?
I've already contacted the support (request ID: 254596), but never heard back from them 
Just checked, the ticket has been allocated to an agent, he will get back to you.
Follow @Dozie and your support ticket first.
But answering your question, "reflowing" solder joints is only re-melting the solder with added flux to help clean the solder and metal surfaces (of rust and fingerprints) for a better bond. You do not remove any components. You can find videos of "reflowing solder" that explain and show this in detail.
(off topic) If you watch youtube, you can see metal casting add a "flux" to pull out impurities from their molten metal that they skim off before pouring a casting.
After soldering, use some alcohol and an old toothbrush to remove the leftover rosin. This will clean up the joints and remove any splatter. Then inspect with a magnifying glass and touch up as needed.
Frankly, while the soldering doesn’t look great, it also doesn’t look so bad that it would cause non-operation. I suspect something else is wrong.
No.
You will never get them all off the board without destroying both the connectors and the board.
I've never heard of that. I assume it's a kit?
Are you sure the bootloader is loaded into the chip?
Check the 5V (that's just the easiest thing to check).
If you have a working Uno, program-in the Blink Example and swap that programmed chip into the unknown board.
And you can also try swapping the "unknown" chip into the working Arduino.
@westfw, you were absolutely right. With the help of the Support Team I've figured out that the capacitors that I had in the package had a wrong capacitance, 47nF instead of 220nF. And being a complete noob (that's the first time I've ever soldered anything in my life) I didn't pay attention to what is written on the capacitors. Hence the UNO didn't work after assembly. Replacing the capacitors with 220nF ones did the trick. My UNO works as expected now.
Thanks everyone for the support!
Yes it is a kit. You can find it here: https://makeyouruno.arduino.cc
The problem occurred due to wrong capacitors that I had in the package.
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