Apple's design error and the reversed capacitor
Briefly

"Brown was finally able to confirm talk that had been rife in the community for years. Apple had indeed managed to reverse a capacitor."
"The mounting of the capacitor - C22 - matches the markings on the PCB. However, rather than a positive voltage, the positive marked terminal is connected to -5V."
"The capacitor might not have been doing its job properly if it was installed backward, but it didn't seem to really be hurting anything."
"Enthusiasts replacing it with a tantalum capacitor might find themselves in trouble, highlighted by instances of incorrect voltage on the -5V rail."
Read at Theregister
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