I have had this Pioneer VSX 402 receiver and Bose speakers for years. Recently the left side has sounded like the speaker was blown. I swapped speakers and found that it was not the speakers but the receiver. I even tried other speakers same result. I hooked the speakers up to B outputs and sames result.
I have vacuumed the dust out of the receiver hoping this would help. I'm stuck. Any suggestions??
If the volume level is equal for both sides (L&R), then there is a problem with the pre-amp section. This could be caused by a bad switching IC (TC9263?) or bad diff-amps. I believe that the VSX402 uses discrete transistors, so I'd suspect the DIFF-amp section. This is a relatively simple repair once the problem is located. You will need an oscilloscope to trace the problem.
Dan
Hello. Chanced upon your inquiry. Although you made it some 3 years ago, I thought I'd try contacting you. I have a Pioneer VSX402 receiver that is exhibiting the same (exact) problem as you describe. The left channel is distorted in a manner similar to a blown speaker. I too verified the receiver as the source for the distortion by swapping speaker connections. I've also been looking for service manual/schematic for the pre-amp area to troubleshoot the problem. I've had no success with the manual, and will likely have to go in bare footed. My question is, did you locate the problem area, and did you restore proper operation. Thanks in advance for any response. Hoping you have a very merry Christmas and Happy New Year, Dennis