John, just read your post, thanks for the advice. I'm sure our Lutheran Pastor would be glad to stop by anytime.
Your similar description is exactly what I'm experiencing. I leave my 600 on all the time. It was not until tonight during the storm that I heard the louder thump thump from like 20 feet away.
I passed it off for thunder in the distance or the dog upstairs jumping off the bed above the HT area. I soon discovered as you did it was the 600. Just powering it off/on for a few seconds dramatically reduced the thump.
Funny thing, when I first turned the switch off, I heard a loud thump. It was almost like I released some electrical charge that was built up over time.
I'm glad the demons have decided to migrate via the internet to your home from Iowa.
