The IEC serial bus on the other hand is handled by the CPU it seems. There is an inverter and some ferrite beads in there, and that’s it. A few pullup resistors as well, but nowhere does the bus cross paths with the audio signal. At least in the schematics.
I traced the audio signal through the whole schematic and this double diode bodge is super sus. The right one shouldn’t be there at all and connects to the IEC port. It feeds directly into the audio circuit. The left one should be there, but wired to the OTHER side of the resistor. What HAPPENED to this board???
I noticed that both bodges lead to the IEC port. So I quickly lifted the lower one. And guess what? The noise is gone. However I still have quite a bit of hiss in the audio signal even when idling. Also it might be that the two other diodes go through the resistor pack. I think I will still remodel this whole area to be the same as on my other board. Plus this board needs a good clean!
Now the board is back to factory. I even removed the janky 3.5mm jack. I didn't like it very much. There is still an enlarged hole in the case, but that's not really fixable.
