I finally got the squeaking noise on one of my Antminer U3' this morning.
In short, it looks like something has gone wrong in the whole miner. So I think the problem is not particularly on the USB interface. When Antminer U3 squeaks, it seems that it fails to draw the power, or something is just stuck and oscillating. I am using
Mean Well RS-150-12 power supply which can supply up to 12.5 A of current with the voltage set at exactly 12 V. So I am quite sure that the problem is not because of the power supply. I am using that power supply as I thought that the brick power supply which comes with the miner has something to do with the instability when I experienced that at the beginning. I guess I am wrong on this.
When the squeaking noise starts, the miner software (BFGMiner in my case) does not realise that. We can only see the hashing rates of the affected miner (AMU 0 in this case) increases (from around 14 GH/s per chip up to 16 GH/s on the picture below). I use that as an indicator that the miner is dying.
You can see the miner LED was flashing on a regular interval and hear the squeaking noise at the same interval on the video on
this link (I have no idea how to properly insert the video on this forum). You also see that the LED indicator on the power supply was flashing at the same interval. The fan was practically not moving due to no power coming to the miner.
FYI, I can only see the video properly being rendered on Firefox browser. After a couple of hours, I gave up trying to figure out why it does not render on Chromium (possibly Chrome as well) and Opera. I didn't try M$ Internet Explorer. So if you had problem seeing the video, I think your best option is to save the video file and play that offline on your video player.