A20-OLinuXino-MICRO not booting

[mrfassi]

My A20-OLinuXino-MICRO does not boot any more.
It worked; I successfully configured the network and installed openmediavault.

It stopped working when I tried to power it down when the LiPo battery (BATTERY-LIPO6600mAh) was connected.
It did not power off, so I pulled the power cord.

After that it did not restart any more.
When powered on, the red led lights on, but the green led stays off.
If I connect the LiPo battery, the orange led lights on when the board is powered.

This is what I tried:
- power it on again;  I've tried with two good 12V power sources, that's why I don't think the problem comes from the PSU
- reflash the micro-SD card
- use another micro-SD card
- connect an Olimexino-32U4 to get the output from A20's UART0, since I don't have a USB-Serial-Cable-F, but with no result (I could have mistaken the program to make the Olimexino forward serial data)

The behaviour of the board is always the same: it stays silent with its red led on; the A20 heats normally, but the board does not boot.
I think I'll order a USB-Serial-Cable-F to see if I can get any info from the board.

Any suggestions?
Thanks

[vinifr]

It is very important that you see the output of UART0. You really should buy USB-Serial-Cable-F. 

Otherwise it will be very very difficult to detect the problem.

[mrfassi]

I tried with the serial cable, but there's no output.

It's a hardware failure.
I've tested the voltages:
5V:   5.4V
3.3V: 0.3V
1.5V: 1.54V
1.2V: 1.24V
IPSOUT: 5.4V

The 3.3V line doesn't work.
It's likely U15 is burnt, or maybe L21.

[dave-at-axon]

If you can get to it, check PIN 1 of U15 as this should be HIGH to enable the 3.3V output.

[mrfassi]

PIN1: 3.26V

[mrfassi]

Suppose U15 (SY8008C(AA)C) is broken.
What about desoldering it and applying directly the 3.3V I need?

I'm powering my A20-olinuxino with the 12V line of a PC PSU with this board:
http://dangerousprototypes.com/docs/ATX_Breakout_Board

I can take the 3.3V from there and apply it to the 3.3V line of the A20 board, once U15 is pulled away.
If it works, I know for sure that I need to replace U15.

[dave-at-axon]

The only issue you need to watch in doing this is the power up timing on the power rails as EXTEN is generated by the AXP209 and I am not sure what the effect would be if there was 3.3V before some of the other rails.

You will need to check this before you give it a try.