Hi As mentioned in another post, the part does claim to have thermal limit built in. They appear to pulse test them at 150 ma and 16V so there is indeed *something* that would suggest operation at 12V would be ok. I’d guess that the thermal regulation spec applies up to 16V and past that you are on your own…..
I’d take a look at the bypass caps on the regulator. Looking back at the original test data, it may have simply gone unstable at the higher voltage. A 0.1 uf on the input and 0.47 uf on the output seem to be the minimums. Bob > On Feb 22, 2018, at 2:48 PM, John Green <wpxs...@gmail.com> wrote: > > For those who have been following the saga of the Chinese made, eBay > purchased antenna that failed, I may have an answer as to why it failed. > I had to destructively disassemble it. I just could not get it apart any > other way. I used a Chinese version of a Dremel tool with a metal saw > blade. After making a huge mess with plastic particles everywhere, it > revealed a circular FR4 board with two patch antennas mounted, one atop the > other. I assume the smaller one to be the L1, and the larger to be L2. This > part looks almost identical to the Trimble Microcentered antenna I worked > on recently. On the back side of this is a metal shield about 3 by 3 > inches soldered to the circular FR4 board. I switched to a abrasive wheel > and took off some of the solder holding the shield to the board. Then, > using a small screw driver, I went around the shield breaking the solder > loose. The shield off revealed that the coax goes to some capacitors that > couple RF out and through an inductor with some capacitors to ground and > finally to a SOT23-5 package labelled LK33. This appears to be a Micrel > MIC5203 3.3 volt regulator. It is shorted on the input side. I believe that > putting anything over 7.5 volts on the input exceeded the power dissipation > rating and caused it to fail. I plan on wiring up a more robust 3.3 volt > regulator in its place and trying again. It looks like I will be able to re > solder the shield back. The watertight integrity is gone for good. I think > I can find a plastic box I can mount it in so I can at least experiment > with it. I have sent a message to the seller detailing my findings. The > Micrel part lists a 20 volt maximum input voltage, so in theory at least, > this might have worked, and there might be some of these out there that > don't fail. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
