[Elecraft] Question about burning odor

[Allen Ward]

Hi,
N3ZDB asked about the source of the burning odor in the KDSP2  in other
words "what was it that smelled?"  My email reply was undeliverable so I
will answer to the reflector as others may wonder as well.
The source of the burning odor was/is R12 the two watt 43 ohm resistor.  All
the current for the KDSP2 goes through it and with normal ~60 ma drain the
power dissipated is 0.155 watts and in my case with 86 ma the power was
0.318 watts.  The extra power made the resistor run hot and something in the
paint or binder in the resistor smelled like something burning.  Some
initial odor
may be normal as Ken K3IU and Michael  N2ZDB both reported that their units
smelled a little at first. With about 50 years experience in electronics I
have smelled many burning odors, but I don't remember any resistors which
smelled with such a low percentage dissipation of their power rating.  Also
the extra current made the resistor pretty hot about 50 degrees C to my
calibrated finger.  Since the resistor was still well within tolerance, this
may not mean anything about the life expectancy of the part.
73 Allen KA5N