New amp is toast

[grease monkey]

Smoke and burning smells aren't good. I don't understand what happened. I just got my TNT 600HD and installed it yesterday. By last night it was smoking. I used larger cable than what came with the amp. I installed a 100A breaker. I ran power wires directly to the auxillary (second) battery. SWR with amp off was 1.2, with the amp on it was 1.6:1. I'm running a 102" with spring and ball mount on the roof of my truck. I used the coax from my Wilson 5K hardmount.
I have my Galaxy 95t2 backed off to a 18W DK and swinging 110W. The amp calls for up to a 20W dk and up to 240W max. So I know Im not over driving it. This is my first amp and I am at a loss. Any ideas?

Only used it to call out my numbers a couple times through out the day. I wasn't keying the heck out of it.