>There are quite a number of threads on this site around discrete sound. What we need as > a proof are recordings taken directly from the audio output. Not from a microphone.
To also add another scenario to this, the pcb could have been repaired using wrong parts when it was in the hands of a prior owner.
It shouldn't happen, but there was a case of during the time when the Congo Bongo external audio samples (broken and not playing MAME at this time) were to be re-recorded by a pcb owner a few years ago. The pcb had a poor repair job with some wrong parts being used on the pcb. The contributor had to undo and remove all the various wrong parts to restore pcb back to its original state before working on recording external audio samples of Congo Bongo.