Mark Zacharias wrote in message
...
"N_Cook" wrote in message
...
Why would a SMPS high speed Unitrode rectifier stud diode 1N5812 , 20
amp,
fail sitting around in a normal human occupation heated environment for
10
years unused?
Currently reads a stable 6.2 ohms. Replaced with a new one but I intend
passing ever increasing current through the old one to see what happens.
Any other ideas concerning cause or analysis ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



I suspect tarnish of interior metals, especially if they contain any
silver.
I see this sort of thing in Euro capacitors and metal connectors,
fuseholders, and the like. I also have to scrape it off the leads of old
semi's that have been in a parts drawer for years.

Mark Z.


Most oxides, sulphides, carbonates of copper silver lead etc seem to be
insulators except silver oxide. I 've not found AgO conductivity , could it
give 6 ohms over the geometries in a stud diode?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/