Some months ago I bought a $15 cheap single-board computer from aliexpress.com named OrangePi PC, with in mind some domotic uses.
I loaded on a brand new 16GB class 10 micro SD card the Debian distro tailored from loboris and posted on OrangePI official forum, and after following all the steps, went right to power up the board. The orange and green leds on the ethernet port lighted on, as well the red led on the board itself, however that was all. After waiting some minutes, the monitor still showed a black screen and there was no sign of life, in fact it didn’t even request an IP from the DHCP server!
Diagnosing the problem
Firstly I tried a different microSD and since both were fine, I went on downloading a different distro but none of the ones I tried worked.
So I powered the board off, picked up my RS232-TTL to USB adapter and connected it to the serial port of the OrangePi PC, setted up the port settings as from the wiki (with just a few changes because I had some gibberish output, probably because by the cheap adapter) and then turned it on.
A TTL serial output example of OrangePi PC
After a few seconds watching the kernel trying to bootup, I noticed it would hang at some point near mid-end process, with the last lines being different each time, but always after the CPU was configured. Thus, thinking of a power problem, I searched through Google for people having the same issues, and found many results and zero working fix, but all agreed that the problem could be related to the DC USB power adapter, despite me having a 2A adapter.
Troubleshooting the power problem and finally booting the OrangePi PC
Checking through the hardware schema sheet, I noticed that the GPIO used the same pinout of Raspberry PI, so reading that the Rasperry could be powered from connecting the pin 2 to a 5v dc power source, I had the idea of connecting my RS232-TTL to USB adapter 5v pin to the OrangePi PC pin 2 while it was connected to the USB power adapter through the DC port (since I had nothing to lose), and magically the boot went on and the login prompt appeared!
After a few succesfull tries, I hypothesized that for some reason the DC port couldn’t suck enough power from the USB port, so after further search, I found some results about thermal issues with the chip and I read that by default, the distros are overclocked, explaining the reasons of such big power requirement.
Having found a possible cause, I went to apply the fix from the serial console, and finally I was able to boot up without having two power sources connected.