My experience is that the plastic ones tend to burn. The mil grade ones in HP I have never seen fail (As in flame)
On Mon, Feb 8, 2010 at 8:05 PM, Glenn Little WB4UIV < glennmaill...@bellsouth.net> wrote: > While in the US Navy, we had to do equipment inspections. > One quarterly was to examine the capacitors in the power supply of one > piece of equipment. > We were to look for leakage (sulfuric acid) from CL65 type wet slug > tantalum capacitors. > Shortly after that CL65 type capacitors were disapproved for military use. > I never saw one that leaked in that equipment, but, have seen a number of > boards damaged from seal leakage on CL65 capacitors. > Something to look out for. > The CL65 capacitors probably have a pure silver case a sulfuric acid as an > electrolyte. > The seal is Teflon. > > We also had an interesting failure mode for ATC ceramic capacitors. > This failure mode will only occur in a sealed environment (submarine. > > Just an observation. > > 73 > Glenn > WB4UIV > > > > At 09:46 AM 2/8/2010, you wrote: > >> The history of tantalum failures is wide and varied, but >> there are some common characteristics: >> >> 1) The tantalum is in a power supply circuit and receives >> a rapid ramp from 0V to operating voltage. >> 2) The tantalum is spec'd close to its operating voltage, >> very close.... 5V on a 6.3V part, 12.5V on a 15V part... >> 3) The tantalum is dry slug, and is sealed with epoxy. >> 4) The instrument has been powered down for an extended >> period. >> >> HP equipment from the 1980's is pretty immune to the problem >> because they typically use hermetically sealed mil spec >> tantalum capacitors. Tektronix equipment from the 1980's >> is infested with tantalum problems because they used the >> cheap epoxy dipped parts. >> >> Tantalum failures are pretty rare in equipment that is >> run continuously. Tantalum has a self healing feature that >> corrects any small problems while in operating... Large problems >> result in detonation. >> >> Dipped tantalum capacitors of any age are prone to failure. >> The tendency can be mitigated largely by never allowing a >> tantalum capacitor to see voltage above 50% of its rating. >> >> And finally, powering a tantalum in reverse, will cause instant >> and irreparable damage. >> >> -Chuck Harris >> >> >> >> Tom Van Baak wrote: >> >>> I powered up a 5071A to watch the end of Loran-C today >>> and was greeted by the special smell that only a mother >>> board could love. >>> Does anyone know the history of tantalum capacitor >>> failures in ten-year old [HP/Agilent] test equipment? >>> This is not my first. Last one was more like July 4th. >>> Thanks, >>> /tvb >>> >>> _______________________________________________ >>> 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. >> > > > _______________________________________________ > 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.