Damage due to nearby lightning strike
Last night, we had a very intense thunderstorm. I had advance warning and was able to disconnect all antennas. We had (at least) two very close strikes. Some electronics were damaged, a router, two ethernet switches, some USB hubs, the common thread was devices with some long cable runs, I suspect currents were induced in the cables. Oh and... one of the KiwiSDRs 😥
There are 7 KiwiSDRs here. 6 are fine, as are other SDRs. One is not so fine. It powers up OK, the Beagle CPU seems good. The KiwiSDR software runs normally, except there are no signals in the waterfall, just static, with amplitude on par with a functional KiwiSDR with no antenna connected. The red overload indicator flickers, even with no antenna connected. I tried increasing the overload setting all the way up to 32768 per 64K samples for the fun of it, no observable difference.
No signals at all on the waterfall, not even the semi local 5 kW 1280 kHz MW station.
I saw the suggestion in another thread to measure across the green antenna connector with an ohmmeter to check for the TVS being shorted. It read open circuit (or at least in the mega ohms)
GPS still works normally.
None of the ICs appear to be running noticeably hot (the FPGA and ADC are certainly warm). No evidence of any arcing, burn marks, etc on the PCB (again no antenna was connected at the time).
Any ideas what the failure mode(s) could be, or what I should check next? I have a scope, so I can check signals, at least crudely. I was wondering if checking the output of U405 would be useful? Hmm... if I can get to them, wow... tiny 😀
Thanks for the link to the troubleshooting guide, John. Here are my results, with a few additional measurements:
66.66 MHz Sine wave, 1.1Vpp, seemed to be the correct frequency. My scope is rated 50 MHz so the actual voltage could be higher.
GCLK Sine wave, 1.6Vpp, frequency looked correct
GSGN/GMAG Present, looked like the images in the troubleshooting guide.
ADC Outputs Most stuck at 3.3V, some at 0V, all appeared to be steady DC signals.
That led me to check some other signals:
L405 2.54V steady DC
L406 0.465 VDC
RF+ 0 V
RF- 0 V
U405 +IN 2.80 V
U405 -IN 2.60 V
U405 VOCM 1.50 V
Might U405 be damaged?