AOC E2251FWU USB monitor flashing
 

I have a mid-2013 MacBook Air running Mountain Lion. Upgraded to Mavericks, lost multi-monitor support, rolled back to Mountain Lion.

I can successfully attach to my Toshiba Dynadock 3.0 with dual monitors via a USB cable, Lenovo LT1421 portable USB monitor as an extended desktop, and Samsung LCD TV as a mirrored display.

I used to be able to use the AOC E2251FWU portable monitor. Starting around mid-summer, when I connect, the MBA screen and the portable monitor turn on and off without success. I think this was due to an Apple software or firmware update.

I have checked the power settings, and tried setting to never turn off the screen, no change. I tried rolling back the DisplayLink driver from 2.2 to 2.1, no change.

I tried plugging the monitor into both USB ports, no change. I tried from BootCamp with Windows 7, no change. I tried on my old Toshiba laptop running Windows 7, and it works no problem.

What can I try next?

I'd try an externally powered hub, or you could try using the USB Y cable connecting the "power only" end to a different power source (not on the same laptop).
Given that the other devices work OK I'd think about a degradation of the electronics more than a SW issue.

Cheers,
Carlo

Thanks Carlo. I'll try the powered USB hub. The monitor has a single USB input, so there isn't a "power only" option for that.

I also found an OS X USB Debug Kit here that I'll try: https://developer.apple.com/hardwaredrivers/

The external powered USB hub worked flawlessly with the AOC monitor. The debug logs contain no reference to DisplayLink. So I think that the driver is not the problem.