I recently purchased a Princeton Graphics HX-12E EGA monitor, and I wanted to get some feedback on its initial start up behavior.

I don't have a 9 pin cable for it yet (it should arrive tomorrow), but I wanted to plug it in and power it on beforehand to make sure that there weren't any surprises. This particular monitor sat in a garage for at least 20 years, and then spent the past 14 months in a basement; to my knowledge, it has not been powered on for over a decade at the least. When I first turned it on, I heard a considerable amount of electrostatic noise. Once that quieted down, I heard an intermittent soft hissing sound from inside the monitor. Does anybody know what this hissing noise could be, and if so, what steps I could take to remedy it (or at least to ensure the safety of both myself and the monitor)?