On Wednesday 03 August 2016 18:14:16 Peter Blodow wrote: > Tin is a very tricky element. It's neighbour in the Periodic Table is > germanium, a semiconductor. Beginning at 13.2 degrees C. going down, > it starts changing its metallic character to a more crystalline form, > almost like powder. At -48 degrees C. it may turn to powder within an > hour. All depending on purity and alloy status. Napoleon's army > experienced this on the way back from Russia to France in the icy > winter of 1812 when the tin buttons of their uniform trousers and > jackets deteriorated to dust. > > I myself experienced this when my refrigerator freezed all its > contents to solid ice a few weeks ago. I swapped the central > electronics PC board, but made no points. After some more > experimenting, I discovered that the NTC sensor cable, where it was > connected to the board, had tinned prongs on the miniature plug. > Obviously, after ten years of service at below 10 degrees C., the tin > coating on the prongs decided to develop some resistance, adding to > the NTC resistance value and causing the microprocessor to run the > cooler down as far as possible. > > I found out by asking lots of people that the manufacturer later had > changed the arrangement by soldering the sensor cable to the > microprocessor board directly..... > > > Peter > An interesting story we all should add to our trivia answers Peter, thank you.
> Am 03.08.2016 17:32, schrieb jrmitchellj .: > > If you follow Gene's suggestion, while you are in the unit, check > > the circuit boards for cracked/stressed solder joints. Over the > > years, heat cycling will cause joints to crack, especially in areas > > that generate heat, like around resistors & transistors. Capacitors > > can also heat up causing cracks. As they age, their ESR can rise, > > causing more heat buildup. > > > > I have repaired countless items by nothing more than reflowing > > solder joints! > > > > If you are allowing your equipment cabinet to rise to 95 before > > cooling starts, the localized rise will be much higher. > > > > Ray > > > > --J. Ray Mitchell Jr. > > jrmitche...@gmail.com > > (818)324-7573 > > --- > Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. > https://www.avast.com/antivirus > > > ---------------------------------------------------------------------- >-------- _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
