Did you make sure the heatsinks were tight? Sounds like heat issue.
I have not taken any of my S3s apart. Is that what you are suggesting? The temp is always under 40C.
It's good practice to always open up a new miner and check boards/tighten up heatsinks and check cable connections before you plug in and turn on for the first time. I've seen very bad things happen when people have not done this. It's a rough ride from China. I'm doing some research about your problem. If I get some info ill post back.