A few months ago I burned up the 4-in-1 ESC in my IRIS+. Didn't do anything wrong that I was aware of, but to make a long story short, armed the quad and started the motors and released the magic smoke.
After a frustrating series of interactions with 3DR support I was directed to where I could buy a new ESC and I did so. Just got around to installing it today and I am having a totally different issue. The ESC replacement went reasonably well. The old ESC was removed and the new one installed with no apparent issues. The cables were inspected to the extent possible and I did not see any damage beyond some scorching and tip damage on the channel that fried. The cables and solder joints for the other 3 channels all looked fine.
Following the replacement I took the IRIS+ outside and got it ready to test. Installed the battery and got a good GPS fix. Connecting to the computer it seemed like everything was working well. Yaw/pitch/roll sensors were good and there were no errors in APM Planner. I armed the quad and it did arm with no smoke. The only problem was that only two motors are spinning. The front two arms are spinning normally, but the two back arms are not spinning at all. Note that the back right arm (when viewing the quad face on) was the channel that was originally damaged in the failure.
I love this quad, but am far from an expert in these devices. Is it possible that something else was damaged in the original ESC failure that could result in both back arms not working? As I said, I get no errors in APM Planner and can perform various functions (mode changes, arm/disarm) so I think the Pixhawk is ok.
I would really appreciate any help or suggestions that people can give. I really do love this quad and would hate to have to junk it.