Telin
100+ Head-Fier
Diagnosis:
Power off a DAC and unplug power cord. Unplug USB cable. Use a multimeter and measure resistance between body of USB connector and a chassis (screw heads). If resistance is 0, and it is stable (pushing a socket body all sides do not break connection), then it doesn't need further attention. No contact or intermittent contact is probably giving all trouble.
Measured my unit and I get a good solid connection between the body of the USB connector and the chassis (also measured directly to the ground pin of the PSU) with a resistance of about 22 mΩ.
Therefor I don't have high hopes the fix will do anything for my problem but I might pull out my solder iron nonetheless eventually when I have some spare time.