Still haven't solved this one...

Tried a variety of different chargers, all created the same buzz.

Under my own steam, the only thing I've left to try are Ferrite chokes, either on the USB cable, the aux cable, or both.
I've read they can be snapped on to cables or one may strip the insulation back and wrap the bare wire around an exposed toroidal core.

If the issue is "dirty power" or a saw-toothed wave, which it seems to be, is there an electrical fix? Installing capacitors? Some sort of DC isolation?
Not my area.


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1981 240D 4sp manual. Ivory White.