I've been trying to figure out why the output transistors keep blowing on an SX-2500 I have. In the process, originally swapped out all the transistors on the amplifier board, and I was getting a single channel working, but I couldn't get anything out of the left channel. I decided to check the transistors again, and all but one of the output transistors had blown. I checked the driver transistors, and they seemed fine, so I put new output transistors in, and turned it back on, but when I did that, R40 caught fire, and R38 got so hot that it discolored the resistor. I replaced the two resistors, and decided to check all the transistors on the board, and found that Q1 and Q2 had blown, so I replaced them again, and pulled every other transistor off the board, tested them, and verified that they were inserted into the board in the correct orientation. When I turned the receiver on this time, I didn't supply any audio signal to them. I just let it stay on for about a minute, then turned it off and tested the output transistors again. They had blown. At this point, I decided to put a signal into the main inputs, and I was able to get weak sound, suggesting to me that the driver transistors are still working. I'm not sure how these problems are related, or if they are related. Does anyone have any idea what might be causing this, and how I can prevent it from happening? I haven't been able to bias the output transistors, because they die before I get a chance. I'm wondering if they might be so badly adjusted that they damage the transistors, even with no sound going through them. I'm not sure what I should do at this point. Any advice would be helpful.