I have only one experience with DeoxIT. Some years ago, the test equipment maintenance department in the factory in which I worked thought it would better maintain the performance of in-circuit test fixtures if the moving parts of the many pogo pins were given a thorough coating of DeoxIT. I became involved while investigating a high number of erroneous test failures. Some investigation led to suspecting the DeoxIT. Fortunately for us, the factory had vapor degreasers that easily removed all of the contact chemical. After removal, function was restored. To my knowledge, there was no appreciable amount of heat involved in these test fixtures, and there was no varnish-like residue. The substance, and most likely an accumulation of dust from the environment mixed with it, made the electrical contact resistance increase and become unpredictable, so that sensitive electrical measurements were effected. As a result of this experience, I've never used this product on any of my equipment. Your experiences seem to indicate this was a wise decision.

In another instance related to protecting contacts in marine use, a customer felt my employer's product needed additional corrosion protection from the salt water environment it was going to be used in. The chassis was opened and mineral oil was sprayed over all of the electronics inside, including an assortment of connectors. When the unit ceased functioning, it was returned for warranty repair. Seeing the slimy coating inside the chassis, we sent the unit for vapor degreasing. After a thorough cleaning, the unit was fully functional. It took some persuading by the Field Engineering department to convince the customer mineral oil was not needed and was the cause of the malfunction.

Unless connections are getting seriously oxidized, simply removing and reinserting should be sufficient to wipe a light surface oxidation from the leads. I would be careful using many solvents that might leave a residue, and most "tuner" contact cleaners contain lubricant which can also play havoc. Alcohol is a good, readily-available solvent that does not leave residue, but be careful to let all of it evaporate before exposure to heat.

Regards,
Bill