Probe PSU output with 'scope again and 10X probe

Use a AC mains scope as was available, means referenced to ground of AC, but should be ground of platform (and hence Fee64)

Figs 1-3: Traces of PSU outputs (5V, -6V, 5V Return) with 10X probe, 1 MOhm impedance AC coupled 
          Lots of fluctuation and jitter

Figs 4-6: DC 1MOhm output from all 3 power rails 

Fig 7-8: Small "loop" using probe and observed scope spectra.

After lunch ideas:

- Try again with 1X probe attenuation, maybe record output to USB 

- Remove unconnected MACBs from master

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