Although Apple (aapl) has not officially announced a fix, moderators of Apple's online discussion boards have recommended that customers try a workaround that involves swapping out the most recent models of the Apple Pro Keyboard for older universal serial bus (USB) keyboards that feature a power switch.
Apple spokeswoman Nathalie Welch told ZDNet News, "We believe (the issue) is extremely isolated and extremely rare. We have taken steps to address it in our manufacturing."
Owners of G4 systems affected by the glitch have been outspoken about their travails. "Apparently, a defective panel behind the power switch burns out," said interactive designer Nickie Bournias. "After this happens, the G4 will no longer turn on."
Other G4 owners have reported the same problem; most of the high-end desktop systems affected by the power-switch issue seem to be the latest G4 towers introduced at July's Macworld Expo/New York.
Customer postings to Apple's Support Discussion site indicate that, in some cases, the circuitry overheats and fails completely, and pushing the power button has no effect. In other cases, the light inside the button comes on when pressed but does not initiate a full startup.
The failure is usually accompanied by the smell of burning circuitry and even small amounts of smoke. Users claim that the burning smell has occurred both when the computer is on and off.
"(At) night, the computer turned itself on," Bournias complained. "The keyboard and mouse would not work at all, and I had to unplug the machine to turn it off. Afterwards, there was a faint smell of something burning. I'm concerned that had I not been home to unplug it, would it have been a fire hazard?"
Software engineer William Kucharski told ZDNet News he also encountered similar problems. "I have used (the computer) a total of less than 20 hours since purchase. Arrived home to find the G4 tower had turned itself on and had hung halfway through boot-up. When I shut down the system, I noticed the power LED in the power button stayed lit."
He subsequently encountered the same problem with his replacement front-panel-case switch circuit board. "The switch was replaced by an Apple authorized service tech. This fixed the problem for about four days or so, when I found the front-panel power switch was dead (again)."
The damaged part was referred to as "Part No. 922-4234 Board, Front Panel" on his repair order, Kucharski said.
Moderators on the Apple Support Discussion site have posted suggestions about the power-switch problems.
According to Apple's support staff, the issue is still under investigation. Users with older USB keyboards can temporarily use the power button on them to power on the Power Mac G4, they said.
Users who plan to employ an older USB keyboard should make sure the front-panel switch remains disconnected from the logic board, the moderators said.
"My Apple repair center said that Apple had told them the front panel board had been redesigned," Kucharski said. The redesigned board, which holds not only the power switch but also the programmer's and reset switch, apparently will not be available before the end of December.
Until then, users who don't own an older USB keyboard could continue to face problems; Apple's new Pro USB keyboard -- which ships with the latest round of Power Mac G4 models -- lacks the power switch Apple support recommends.