Most of this type of receiver uses an integrated 15-18 pin SIP-M output device. Usually, they are in pairs - one for the "main" speakers, and another one (plus a discreet device) for "rear" and "center" channels. My best advice is to skip the Sony factory service, and find a compentent technician where you can drop it off and at least have it honestly evaluated. When items such as this come to my bench, if I feel it is too labor intensive to either find or repair the fault (not to mention replacement parts cost...not too bad if you are replacing components; really bad if you are replacing semi-obsolete boards) - I simply tell the person, "It's not worth fixing". Good luck.
-Richard
-Richard