Apple III - Design Flaws

Design Flaws

Steve Jobs insisted on the idea of no fan or air vents – in order to make the computer run quietly. Jobs would later push this same ideology onto almost all Apple models he had control of – from the Apple Lisa and Macintosh 128K to the iMac. To allow the computer to dissipate heat, the base of the Apple III was made of heavy cast aluminum, which supposedly acted as a heat sink. One undeniable advantage to the aluminum case was less RFI (Radio Frequency Interference), a problem which plagued the Apple II series throughout its history. Unlike the Apple II series, the power supply was stored – without its own shell – in a compartment separate from the logic board. The decision to use an aluminum shell ultimately led to engineering issues which resulted in the Apple III's reliability problems. The lead time for manufacturing the shells was high and had to be done before the motherboard was finalized. Later it was realized that there wasn't enough room on the motherboard for all of the components unless narrow traces were used.

However, many Apple III's experienced heating issues, allegedly caused by insufficient cooling and inability to dissipate the heat efficiently. To address the heat problem, later Apple III's were fitted with heat sinks. But still, the case design made it impossible for enough heat to escape. Some users stated that their Apple III became so hot that the chips started dislodging from the board, the screen would display garbled data, or their disk would come out of the slot "melted". In a technical bulletin, customers who were experiencing certain problems were instructed to lift the machine 3 inches (76 mm) and drop it in order to re-seat the chips on the logic board. Jerry Manock, the case designer, refuted these case design flaw charges and maintained that the unit adequately dissipated the internal heat, which he proved with various tests.

In the end, Manock was vindicated, as the primary culprit turned out to be a major logic board design problem. The logic board used "fineline" technology that was not fully mature at the time, with narrow, closely spaced traces. When chips were "stuffed" into the board and wave-soldered, solder bridges would form between traces that were not supposed to be connected. This caused numerous short circuits, which required hours of costly diagnosis and hand rework to fix. Apple designed a new circuit board – with more layers and normal-width traces. The new logic board was designed by one designer on a huge drafting board, rather than a costly CAD-CAM system used for the previous board, and it worked. With normal-width traces there wasn't enough room for all of the components, so a separate daughterboard had to be designed for the RAM which would fit within the existing heatsink.

Earlier Apple III units came with a built-in real time clock, manufactured by National Semiconductor. The hardware, however, would fail after prolonged use. While it was assumed that a vendor would test parts before shipping them, Apple did not perform this level of testing. Apple was soldering chips directly to boards and could not easily change out a bad chip if one was found. Eventually, Apple solved this problem by removing the real-time clock from the Apple III's specification, rather than shipping the Apple III with the clock pre-installed, and sold the peripheral as a level 1 technician add-on.