fail is due to leaky capacitors. For a few dollars could order the parts and try that repair yourself. Would need a decent soldering iron and de soldering tool or copper braiding to wick off the old solder. The concern buying a used amp is it probably has old capacitors anyway - with eventual failure due to summer heat cycles.
Certain capacitors (electrolytics) have a + and - polarity so new ones need to be installed with the same orientation on the circuit board.
