Tracking down "crackling" noises in monitor

Picked up an old terminal in very nice cosmetic condition; it works fine barring a bit of visual "jitter" on the display -- not sure how best to describe it. The picture is clear and sharp but occasionally a few scanlines will spike off to the right a bit. Coinciding with this spiking are tiny crackling noises from inside the monitor. (Or at least it seems like they coincide, obviously I can't verify this.) I thought it might be HV leakage based on discussions I've seen on this list. I've run it with the cover off and the lights off and I can see no evidence of sparking or other visible discharge. Any thoughts? I hate working on CRTs. I'm not great with electronics (getting slowly better) but I can handle debugging low voltage stuff. Fixing monitors scares the heck out of me... - Josh