I have hundreds of Germanium OC71's , now useless although perfectly
alright when bought perhaps 20 years ago, stored indoors in normal
human comfortable conditions.
Looking under a microscope and probing it would appear the
C-E shorts are due to metalisation creeping over the die.
Over the years I've found a few times that those, usually 3 lead, ceramic
resonators can fail by going resistive over the edge of the thin element as
though the metalisation has crept around the edge.
Is this a recognized failure mode and anyone know the proper term or where I
could research it ? Whether silver or Al or both have this effect ?

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