My board can't start

[Bartchou]

Are you working on a breadboard or PCB ?
Breadboards, especially OLD ones often suffer from stray capacitance and poor connections. Darrel once told me he ONLY used brand new boards. I have disassembled several OLD breadboards to find a surprising amount of corrosion in the fingers.

Hello,Archangel
Yes ,I'm work at Nexpcb--PCB fabrication, PCB Assembly, PCB Turnkey Service.
For breadboard, this situation is common occurrence, especially wet environment.
It would be better if covered the Conformal coating on the new assembly board.