Quoted from DennisT:
Here’s an update. First, both boards have been recapped (electrolytics). Just for the heck of it I replaced the tda2002, no change. The last thing I just tried was to see if it would hum in another game. So I installed it in my Contact pin and it is as loud as when it’s in Flash. Now here’s the weird part. Contact has the older type 1 version 1 board in it. When powered up it has the same loud hum but only for less than a second then it goes away, like a cap charging. I think the next to try might be pulling the caps and checking them to make sure they are what their supposed to be.
Any updates? I just acquired a Flash machine and I have what I think is the same hum. If I power up the game and it’s in attract mode it’s pretty darn loud.
I’m sending all my boards out for a refresh and we’ll see it that happens to help or not.