Hi I’ve seen the same failure on Efratom LPRO Rb’s on the input bypass cap.
It’s a pretty common failure in general. Tantalum’s don’t really like very high surge currents / rapid voltage ramps. In normal bypass applications, restricting current surge / voltage ramps may be a bit tough on the power input side of a system. Bob > On Apr 11, 2015, at 12:52 AM, Chuck Harris <[email protected]> wrote: > > That is almost a carbon copy description of how I fixed a > similar module in my Ball/Efratom MGPS unit on my GPSRb > unit. > > An oven set to 140C is your friend when doing jobs like > this. > > The guys that make these modules are trying to make them > as small as possible, so they always use tantalum capacitors, > and run them very close to their ratings... in this case, it > was 18V on a 20V cap. > > This particular module had +/- 15V, and +5V on board. I have > never seen so many individual switching power supplies stuffed > into a single module... They were all little 5 terminal IC's, > with each running at whatever frequency it felt like... > > -Chuck Harris > > > > Bob Stewart wrote: >> This is just a brief report, not a how-to. >> >> I got a KS_24361 with a bad Lucent power module. Having nothing to lose I >> thought >> I'd see if it came apart. After unsoldering it from the motherboard, I >> found the >> usual potting compound. Fortunately, the compound was only loosely attached >> to >> the board in the brick and was easy to pick off. After that, I used a pair >> of >> needle-nose pliers to work the board out of the casing. In spite of the pic >> below, I first gently pried up on the corners, in succession, until the >> corners >> released. Then I worked my way toward the middle, until the board came out. >> Be >> aware that there are two small inductors on the top side of the board that >> have >> metal covers that will probably stay in the potting compound. Just leave >> them >> there. When you push it all back together the covers will go back on the >> inductors. >> >> http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot >> while >> I had it on, so I figured there was a shorted component. As it turned out, >> it was >> a 15uF tantalum cap with a big brown spot on it. >> >> http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board >> at the >> upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg >> >> So, ordered the cap, put it on the board, then just pushed the pins into the >> motherboard for testing. I didn't even bother soldering it. >> http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the >> board >> back into the casing, and soldered it all back on the motherboard. I didn't >> bother repotting the bottom surface of the board. I attached the repaired >> KS to >> my good REF-0, and it's now working. Bob - AE6RV >> >> _______________________________________________ time-nuts mailing list -- >> [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the >> instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
