My Fire! game makes a loud buzz sound through the speakers for about a 1/4 second once it is powered on, especially after it has been off for a while. If I turn it off then immediately turn it back on, it doesn't make the sound. It's as if there is a capacitor that's draining when it shouldn't or something not quite workign right after the game has had some time the "rest" with the power off. I've replaced all the caps on the power supply and sound board, but no other components. Any idea what else to look for or what could possibly be related? The game operates ok; it's just that this sound is a little annoying turning the game on and a bit concerning that something is failing (maybe leading to more trouble).

Thanks for the tip on the ground. I got this game a couple months ago and haven’t done a lot with it yet other than the caps, a few LEDs I had on hand and new rectifiers/fuse mod. I’ll check for grounds. Btw, here is a video showing the buzz on startup:

Good tip, will do. I've since noticed that it seems a little more inconsistent as to how much time it needs to be off to make the sound when powering on. I'll check out the grounds and try to isolate the sound card and see what happens.