A friend of mine brought me an SX-2500 that he had some issues with, and I am to a point where I need to see if it's worth fixing. It presented with no sound from the A channel, and very quiet sound from the B channel. I checked the fuses, and the fuse was blown for the A channel, so I checked for a short and found that one of the output transistors was blown short. On the B channel, I tested the output transistors, and one of them was blown as well. I then checked all the driver transistors, and two of them were blown. Because of this, I decided to just replace all four driver transistors, and all four output transistors. Now, after replacing the transistors, I tested the voltage going to them. I expected to see the same voltage going to both channels, but instead I found around 35 volts going to the output transistors on one side, and 97 volts going to the other side. Not having anything telling me what the voltage should be here, I can still assume that both voltages should be the same. I had also tried to get sound out of the speakers, and only got sound from the B speakers again, but it was still quiet. I hooked my oscilloscope up to the driver transistors, and noticed quite a bit of distortion of the type that suggests to me that possibly capacitors are bad somewhere. I also see no way to tune the power levels, so I am assuming that there is a bad component somewhere that is either adding resistance, or reducing resistance. Now, here's the problem I need advice on. After talking to this guy, he says that he paid someone else to recap this amplifier. I had noticed that there were signs of someone else having worked on this before, but I didn't see signs of a full recap. I only saw that a few caps were newer style caps, and most were the old smooth top Nippon Chemicon caps. This other guy, that charged him for a recap that was never done, was supposed to have attempted to repair the problem he brought it to me to fix, but wasn't able to do it. Now, given that I'm no real professional when it comes to repairing these old receivers, and I was able to diagnose some bad transistors, at the very least, I'm thinking this guy he went to didn't have a clue what he was doing. That makes me hesitant to try to go any further on diagnosing this thing, because I don't know what he tried to do. My first reaction at this point is to hand the thing back to him and tell him to cut his losses, because I don't want to go and figure out what this other guy did or didn't do. On the other hand, this could be something that can be easily fixed. Does anyone have any suggestions as to where to look, or whether or not to give up?