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5:10pm
Omar found that one of the LV mezzanine card (L5t, bottom screw) was now connecting AGND to the FEB support plate. After debugging turns out that it was the edge of the high-speed mSAS cables that was conducting and touching components on the FEBs.  

TKN - my notes on this

  • Omar found flaky short to plate on one FEB
  • Investigation revealed edges of data cables could short to components and/or mounting screws 
  • Ryan reminded us that the data cable shield is connected to ground in the cable (and thus to FEB ground).  So, likely that a cable edge was simply touching nearby screw.
  • All data cables passivated alongside FEB cooling plate as per note 7 on cable data sheet (doh!)

5:30pm
L4t and L4b power was swapped on the back of the breakout box (on the flange side). For reference this is patch panel P3 and thus S1 and S2 where swapped. Mapping power to FEBs is ok now.

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