help fix bosses stereo

[tim in pa]

my first post, thanks for reading. i am repairing my bosses (i know!)vintage receiver, pioneer sx950. while tracing some crackling, i had my o-scope (x1) probe on the pre-amp output (amp input) comparing the left and right signals. when suddenly, the audio (both l & r) sounds like it is now coming out of a tin can. i do have the sams schematics for this unit. the only thing i can think of is that the scope probe loaded down the signal (did it load the input side of the amp or output side of the preamp). the problem i have here is that there are signals present at all stages, i just don't know if they are correct. your help here will be greatly appreciated