I recently bought an X5 and a Lightbridge 2. I was waiting just for the N3 to put all together. Yesterday the N3 finaly came. I put everything together on a S900 frame.
1. The transmitter on the Lightbridge2 wont even power on, so is no way for me to test further.
2. The X5 is doing a constant grinding noise very weird, will power on, do the dance, and after all motors get limp.
I verified all cables for continuity, I thought maybe one of them is broken...all look fine.
On facebook support DJI page , they told me to try first and upgrade the firmware.
As instructed I tried the Matrice 600 firmware.
result:
2014.01.01 00:00:06 remo-con disconnect======
Packet: MATRICE600_FC550_FW_V01.10.01.40.bin
Result: Corrupted.
Firmware bin file is corrupted, download it again from the DJI offical website.
After I tried the Inspire 1 firmware, this time was doing something but at the end said :Failed.
I tried few times, I downloaded few firmwares, I changed the cards, I format FAT 32, ........nothing.

Can somebody tell me. The lightbridge2 is taking the power from the X5 and this is why doesn't power on?
All items brand new out of the box never flown.
Thank you in advance for helping.

When you try to turn on the RC, will the first press provide the battery level? As far as the X5 firmware is concerned, you will not be able to update it with the rig you have. The use of the M600 X mounting bracket outside of the M600 is still a mod, and there isn't a firmware package for users that use the standalone A3/LB2 combo instead of the M600. The X5 can only be updated via the Inspire 1, OSMO, M600, or M100. You would need to either get in contact with a local dealer or borrow one of those platforms from a friend, if possible, in order to get the camera updated. You can also send the camera to DJI to get updated as well, but of course the former is a more immediate solution.

Ok...bigger problems then the update.
The Lightbridge 2 didn't power at all was just dead, after hours of investigations with multimeter on continuity for cables, the cable what goes to N3 was not right. After further inspection with a magnifying glass, pin 4 from the right was not going to the end. I bridge with a paper clip and evrika everything lighted up. That is really crappy quality control and I am sure nobody tested that lightbridge 2 before sending it out, was brand new. Now I put the pin in with a needel but I ned to get a new cable, I do not trust that one.
Huh what are you talking about? Is written on the DJI page, X5 compatible with N3, and LB2 I bought the recommended combo....what mood we are talking about?
What local dealer , what to send it back, the recommended firmware was wrong and didn't work. As recommended by one of your guys at support "try the Inspire 1 firmware RAW" you have nothing to lose. I tried that and worked as a charm no problems whatsoever. So you are saying something the other guy from support something else....where is the right decision. Still testing, will see if everything works.  I like this digital less and less...........old A2, Naza 2 with futaba 14SG never ever crashed on me and were far less problems.