I picked up a Setton RS-660 about a year ago and finally had a chance to examine it. It flickered many times upon startup but then the relay would finally kick in. Pulled out the Bose 901's series 1 that I never played. I enjoyed the sound but noticed that the Setton was getting pretty warm with the sound dial at 9 - 12 o'clock. I just figured it was old inefficient 70's output transistors. Did a little research here and found a post by k7sparky with pictures of the power switch and how to cure the problem. Didn't have to remove the faceplate to get to it and took k7sparkys advice by taking my time. Opened up the power switch and saw two sets of contacts that looked like old style ignition points. They can handle high voltage but I don't think they can handle the amperage that this monster demands. Cleaned out all the black ash with Q Tips, contact cleaner and brass brushed the contacts. Slapped it together and no more flickering or relay chattering. I noticed that the heat was at a minimal at the same volume settings. I'd like to believe that the reason why she was running so hot in the beginning was because it was staving for amperage and the output transistors were working overtime to produce the output. So, if your Setton is running hot, clean those contacts in the power switch before you blow those almost bullet proof transistors.