[Elecraft] "One of my 2SC1969's keeps overheating"

[Allen Ward]

I had a burn out of one 2SC1969 in K2 #1107.  I carefully inspected the
rubber insulator/heat-conductive pad and the shoulder washer and all
hardware.  In my case the screw had rusted a slight amount and caused a
leakage path to ground.   Eventually the shoulder washer melted and the
transistor bit the dust.  I have, over the years, replaced many transistors
with similar problems.  My suggestion is always replace both transistors of
a pair.  Replace all insulators and hardware.  Make sure there are no burrs
or rough places that might puncture the insulators (a sharp edge under
pressure will eventually short something out).  Hardware should be tighten
firmly but no so much force used as to crush shoulder washers.
Last but not least ... sometime things just fail without an obivious reason
and bigger fuses don't cure problems.
73 Allen KA5N