Just posting this repair note to the AudiogoN archives - in case another owner has a similar issue.
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My Dayton Audio SA 1000 subwoofer amp (7 years old) suddenly developed a very loud & scary high-pitched tone – well above 60Hz. On the phone to Dayton support, the tech offered a very weird response. He said: ‘Congratulations. It’s now a boat anchor.’ I asked if it can be repaired. He replied almost amusingly, ‘We don’t repair boat anchors’. Huh? That was one of the strangest chats I’ve ever had with any tech support.
Before tossing it overboard, I did a Google search. It turns out that the capacitor in the C6 position on the power circuit board is known to go bad. (The boards are well labeled.) Capacitor replacement cost $2. DIY labor cost: $0.
The amp is working great again. It does a very good job of driving my subwoofers. The built-in EQ is really nice for integrating the subs with my main speakers. I do recommend it spite of their tech support. It helps if you’re comfortable with a soldering iron.