XO4 B1 ECOs

From OLPC

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.

[edit] 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)

[edit] 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.