Hi to all,
Just wanted to share my findings, it could be of use to someone.
Few weeks ago I noticed sudden drop in number of aircrafts and as my setup C.H.I.P. & FA pro+ was working 24/7 quite some time I decided to check logs first to inspect software first. I saw that dump1090 was running but there was no data and log was full of messages “No data received from the SDR for a long time, it may have wedged”.
Since C.H.I.P. has only one USB port I checked it and found it was quite dusty.
OK, just quick check, antenna was ok, cables connectors all ok, and measured power supply with fluke multi meter and it was steady at 4,9V at input and 4,85 at USB port.
I disassembled FA stick, at first, nothing suspicious, solder on SMA and USB connectors was ok.
I “washed” everything in ultrasonic bath with isopropyl alcohol and assembled it next day.
To my surprise errors showed up again, dump1090 produced some data for 2-3 minutes, than error repeated. On every restart it was working few seconds to minutes…
So, dead dongle?
I put it in windows machine directly in USB port and it was working longer but still acting strange, it hangs after 10 or more minutes, but lasts more than C.H.I.P. Quick look again and measurement, I found that my PC is putting 5,1V on USB and that gave me idea.
Removed 2 electrolytic capacitors and measured them with cheap LCR meter, they were labeled 10V 220uF and measurement showed 70-100uF, nothing near declared capacity. I didn’t have new 10V cap in my spare parts, so I put 16V but same capacity. Because it was little bigger, I soldered it at 90-degree angle.
And voila! It works! For last 3 weeks it didn’t stop not a single time.
I was prepared to throw away dongle because I had few others used on other projects, from generic plastic ones, some of them died in similar way because RTL2832 chip dies. Those generic have no cooling, no solder on thermal pad below chips, poor quality power supply etc. V3 from rtl-sdr.com is great solution for long run but there is no filter for 1090 or LNA in it.
So, after few years of constant use I recommend changing those capacitors and if some of you did have similar issues don’t throw it away because this could be cheap fix and should work for few more years for sure.
Handy to know! I noticed the dongle runs warm which will reduce the life of the capacitors. I imagine dongles stuck inside a masthead enclosure beside. Pi might get quite hot and if those capacitors present an issue, it may be sooner rather than later.
The Pi itself can have those issues too, when exposed to the heat of lower latitudes. The folks in Canada, UK or Germany might not care about that tough
Indeed! I’ve got mine indoors and the ambient temperature is 10 degrees - the joy of houses about 150 years old in the UK! It’s surprising how long our electronic appliances seem to last
I forgot to mention, my setup is in metal enclosure near window (part of day is direct sunlight) and stick is in wrapped aluminum foil. I have a lot of EMI/RFI from GSM equipment that I use at work, that is why stick is wrapped. I added thermal paste and 2 heat-sinks (one for R820t2 and other for RTL chip) and there is a fan inside to keep it cool.
I have few Pi-s but I don’t use them for ADS-B, I was lucky enough to get one of C.H.I.P.-s at beginning of their campaign and it was perfect fit for enclosure that I had at time. Temp on allwiner chip never crossed 45C.
And one more thing. I tested ~ 20 different power supply, from cheap ones to pro, some were too “RF noisy” others were too big to fit. Bad power supply can kill devices especially weak or bad capacitors. One capacitor that I replaced had big ESR value (Equivalent Series Resistance) and probably that is also why stick failed.
It is good practice if you use gear 24/7 once in year to rip everything apart and clean it, check RF cables, power supply etc. Pay attention on PS capacitors on input/output if it is switching power supply. That could be change in color (from high temp) or they can look swollen or bulged and often with leak and unpleasant smell. Often you can hear high frequency sound buzzing and noise when you put load on it. That could be sign that power supply is going to fail.
I wish power supplies weren’t permanently sealed in their case as seems to be common nowadays. All too often the capacitors are cooking away unseen and the opportunity to swap them out with something better is thwarted by the sealed cases!
I believe we’re switching out some capacitors on the next PCB revision of the prostick, I think it might be these ones - let me check. (edit: yep, those were the ones)
Electrolytic Capacitor: That’s the element that also damage the LED drivers when working under extended periods of high temperatures. Whoever sees a blinking LED light fixture is looking at one defective capacitor.
Solid dielectric like tantalum are more expensive but, properly burned-in, solve that problem.
