On September 17, 1992, Apple recalled 60,000 PowerBook 100s because of a potential safety problem. An electrical short, it was discovered, could melt a small hole in the casing, which occurred in three of the 60,000 notebooks manufactured between October 1991 and March 1992. On the day of the recall, Apple shares closed at $47, down $1.25, but some analysts discounted the recall's importance. In addition, the original power supplies had problems with insulation cracks that could cause a short in a fuse on the motherboard; and the computer was prone to cracks in the power adapter socket on the motherboard, which required a $400 replacement motherboard if the warranty had expired.