If an instrument is "rode hard, put away wet", then there could be all sorts of failure modes from salts creep across some leads, corroded traces (especially across SMT chip connections) and similar. Where the failure showed up is not necessarily the first-cause.

I have seen situations (as recently as this last weekend) where an individual carried a tube tuner from his car to my clinic table in Kutztown for testing. What he did not understand was that it was a very hot and humid day, and he was dripping seriously through the cover into the guts. I did notice the sweat and cleaned it off before applying power. But had I not noticed - between the salts in the sweat and them corroding traces, can you say *POW*. Note that should there be some source of salts, these are naturally deliquescent - every time the humidity rises, the damage will go further.

Just a thought.

Peter Wieck
Melrose Park, PA