You can do whatever experiments with the new ones that you'd like but I think you agreed to buy guaranteed quality parts from Mouser for the final repair.
After my latest tests with heatsinks and better cooling I was beginning to conclude that the new transistors were working as expected when compared to the original transistors. So I was going to use the new transistors for the final repair.
Just wanted to close the thread. The problem was resolved after installing new genuine output transistors for Q2-Q6. Thank you Perry for all your patience and help. I learned a lot.
