Static electricity discharge (like when you walk across the room and then get shocked touching something) isn't visible until it builds up to several thousand volts. Most static sensitive components can only take about 60 volts and still survive. More insidious is the partial breakdown of components that can occur from minor discharges of lower voltages. These can cause components to fail or become intermittent at later times. Keep this in mind the next time you are thinking of opening your equipment for any reason. Make sure you ground yourself to a grounded metal casing or frame to get rid of any static charge on your body. Or better yet, use a grounded wrist strap whenever you are working inside electronic equipment.