All, it is very possible that this debris on the PCB is a Urethane
product. It was popular for adhesive use, for open cell foam cushions,
and making washers, etc.
Urethane ages poorly in humidity. It becomes gummy, and we call it
"foam rot". It is hydroscopic, ie picks up water from the air.
The by products are then tenacious to remove.
Wash hands after dealing with Urethane problems.
Urethane adhesive was a big problem to my tape recording industry when
tapes turned sticky on the back face. There, we use controlled heating
to temporarily stabilize the urethane sticky products to something that
can be removed more easily.
Stuart Rohre
K5KVH
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