XO4 B1 ECOs

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These are recommended engineering change orders (ECOs) to the B1 prototype of the XO-4 laptop. This is NOT a list of changes from B1 to C1, that is located elsewhere.

Improving system noise margin

In the B1 laptop, ferrites are needed on the keyboard and touchpad clock lines running to the EC as there is insufficient input capacitance on a number of power supplies, resulting in excessive ground and Vin currents. This is solved by increasing the amount of input capacitance at a number of voltage switchers:

  • Add two 10 uF ceramic caps and one 0.1 uF cap in parallel with PC91, near PU8 (Vcore)
  • Add one 10 uF ceramic cap in parallel with PC128, near PU11 (Vmem)
  • Add one 10 uF ceramic cap and one 0.1 uF cap in parallel with PC75, near PU5 (+1.8V)
  • Add one 10 uF ceramic cap in parallel with PC87, near PU7 (+3.3V)
  • Add one 10 uF ceramic cap in parallel with PC52, near PU4 (+5V)

Speaker Rattle

The speakers on the B1 units (especially the right one, but both have come loose) are likely to come loose. It is recomended to re-attach them using a high strength epoxy. Spread the epoxy in the circle behind the speaker. Be careful not to glue the speaker back too close to the edge of the laptop --- it can interfere with the bumper.

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