I made the same upgrade from an LS 27 to a Ref 5 SE and it is a significant upgrade. It also seems like it is a better impedance match for the Ref 75 (now Ref 75 SE).
I would contact the seller and see if they would be willing to cover the cost of repairs or split them. This is a small hobby and many people are understanding - we've all had a problem.
4 years ago I had an issue with the power supply in a VSi60. When the amp warmed up I got an owl sound. It turned out two resistors in the power supply had gone bad. I think they charged me for two hours of labor which included a chassis repair (my dad dropped the box while helping me move) plus return shipping. You're looking at $200-$300 plus shipping both ways.
I don't know your financial situation, but it you're buying this kind of gear you aren't worried about putting food on the table. Hopefully you don't need to sell the LS 27 right away and can let ARC fix the issue.
I would contact the seller and see if they would be willing to cover the cost of repairs or split them. This is a small hobby and many people are understanding - we've all had a problem.
4 years ago I had an issue with the power supply in a VSi60. When the amp warmed up I got an owl sound. It turned out two resistors in the power supply had gone bad. I think they charged me for two hours of labor which included a chassis repair (my dad dropped the box while helping me move) plus return shipping. You're looking at $200-$300 plus shipping both ways.
I don't know your financial situation, but it you're buying this kind of gear you aren't worried about putting food on the table. Hopefully you don't need to sell the LS 27 right away and can let ARC fix the issue.