The buzzing is caused because the sustain boards draw current at about 60 Hz x 28 fields/frame = ~1.7kHz. i.e. the load modulates the current at about 1.7kHz. I am relatively sure the capacitors are all OK. (It has enough of them, plus only the big four - Nichicon, Chemicon, and Rubycon mostly, with the primary caps being Hitachi.) The TV & Vsus section is otherwise fine (steady 210V at full load white, not varying under load.) Normally the transformer should not make this noise. Most Kuro owners start having this problem after a few years.
See picture for the panel sustain waveform for the common electrode drive. Lots of opportunity for noise to leak everywhere. The sustain boards do gently buzz but not very much.
Pioneer did not cheap out on this set...