With respect, the internal deguass is done every time the tv is turned on. Wheather the tv was off for 30 seconds or 30 minutes. The boing that you hear is the tv warming up.

If you feel comfortable, take the tv apart and dust inside. If you do take the tv apart, the ONLY way that is safe is to wait at least a hour after it's been unplugged, AND place the tv on it's face. Because in most tvs, the back panel supports the tube. When dusting, be sure that you use a duster that is not made of metal. When I do this to my tv, which is once a year. I feel very safe, because I've been shocked by 10k before, low amps of course. So I know what it feels like. But my heart rate is still a little high. When I clean the inside, I actually use glass cleaner and paper towel over every thing. If your vac can do this, attach the hose to the exhaust to blow any dust out.

Rob