Matt, Thanks for the tips on the power supply. I was worried that the quality of the wall wart may have played a part in this – unfortunately I don’t have the equipment necessary to inspect its output closely. I’ve also seen incidents of tantalum capacitors that have almost seemingly spontaneously combusted before with little or no evidence of a poor operating environment, so who knows.
Thanks again, Billy From: Radio User [mailto:radiogeek...@gmail.com] Sent: Saturday, September 23, 2017 10:08 PM To: usrp-users@lists.ettus.com; Billy Jones; Robin Coxe Subject: Re: [USRP-users] C674 fail on B210 rev 4 Billy, On Fri, Sep 22, 2017 at 8:23 PM, Billy Jones via USRP-users < usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> wrote: snip > I'm using Rev 4 of the B210, and I have a GPSDO-TCXO module installed. I > was using a 9V, 1.5A wall wart as the power supply and had the USB3 cable > connected to my PC. > > Thanks, > Billy It is possible that the cap failure is "just one of those things" but your comment about the 9V wall wart may be important. There are some pretty gross wall warts out there. Some even manage to produce not-very-good-almost-DC with lots of hash. Others have poor isolation between one of the output terminals and the input (mains) connection. The UL or CE tag on the case may just mean that Uncle Larry or Cousin Eddie signed their names to it. I long ago avoided the problem for my N200 (6V DC) with a very high quality DC/DC converter driven either by a not-so-portable battery or by a lab power supply. I often run my B210 from a 12V linear bench supply. I'm assuming your 9V wall wart was supposed to produce DC. It is likely a switcher. (Designing an affordable well regulated linear DC supply that can source 1.5A is hard if it has to stick to the wall socket.) Switchers are fine -- when they are well designed. In fact page 7/8 (the last page in the B200 drawing set) shows two very nicely designed switching converters to generate the 1.2 and 1.8 volt supplies for the FPGAs. Badly designed or cheaply made switching regulators, however, are noise generators, and not very good at that. They have spectral peaks all over the place, the spikes up and down in frequency, and they are dirty, wide, and rich in noxious harmonics. So, unless your 9V wall wart was particularly clean, you might try a good bench supply or a stout battery. You'll get a cleaner RF environment and may even save some wear-and-tear on the input filter caps. matt
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