http://home.graffiti.net/diverse:graffiti.net/crack.jpg
Is a microscope view of the crack. Now viewing magnified it can now be seen
the fault developement.
The just left of centre part of the crack must be part of a crack that
formed initially but enough current flowed in the other parts making
touching contact until there was too much localised fusing.
1 to 1 marks the 1mm or so of conductor between the 2 straight line
etching/millings ? into the conductor to form part spiral paths.
The C marks the end of one of these formed breaks and there is another one
on the other track , off the top left of the image, giving about 1 x 1mm
central fusible conductor.
Nowhere on the remaining conductor is there any discolouration due to
overheating



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