About a month ago, our USRP1 Rev. 4.5 (Ser. #2728) became erratic in it USB connection and communications. A short while after, USB failed altogether. I put scope probes on the USB + and - data lines and observed that one of the signals had a much different sort of signal than the other. Following advice from Matt Ettus given to others who had experienced USB failure, I ordered a replacement USB chip along with a Chipquik SMD removal kit. Replacement of the chip had no effect, so I was forced to look more carefully for a cause. It turns out that one of the 0603 capacitors installed near the USB receptacle (C73, C74) was shorted, and removal of these 2 capacitors restored USB function. I'm posting this description of my experiences for the benefit of others on the list.
I suspect that C73 and C74 (which I can't find in various schematics and BOMs for USRP1) were added in the hope that they would provide a path for electrostatic discharges, which is ironic. In my experience, low-capacitance avalanche breakdown devices are more suitable for this purpose. I can highly recommend ChipQuik. Paul Mathews _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
