Audio Systems: American Legacy series 2 LA890 amp, faulty processors, legacy series

Question
During instal when power connected smoke came from amp. Sec. later during power dis connect both 20a. fuses blew. Did not reconnect- checked wiring-found grounded + speaker wire.Cannot figure out how that happened except for poor quality of installer! Dismantled amp and found 2 burnt 1AFZ34N.A grounded speaker wire should trigger the protect circuit and not fry the processors-yes. If so what is the under lying cause.Since I will not be taking this amp to the place that "repaired" my CD unite I though it might be faulty processors and replace them my self since this is not a difficult task. Finding 1AFZ34N-easy...replacing 1AFZ34N-easy..knowing why they fried-not so easy. Looking forward to your opinion. TKS

Answer
First guess is the power connections were reversed (ground and 12v lines).  Second guess is the speaker(s) have a ground connection on one of the lines (easy to check).

If it smoked when power was connected and BEFORE it was turned on then it must be a wiring and/or grounding problem.

Any other comments that will help me to understand what happened?  These amps are very robust and if connected to power properly and speaker systems/wiring is correct it is very hard to blow the up!

Tell me more after checking out the above "guesses".