What is Moisture and Corrosion, and why is that bad?
Moisture is the presence of water in trace amounts. It can cause rot in wood and corrosion in metals, both of which are the main materials in your amplifier and cabinet. When moisture goes inside the amp it can corrode the input and output jacks (causing intermittent crackling, popping, and volume loss), damage the cables inside the amp, and short traces on the circuit boards. If corrosion is present on any of the jacks, the best thing to do is to replace them. For light corrosion, applying contact cleaner to the jacks will help.