I used my 1Mac g5 1.6ghz./2 gig DDR for simple home audio recording. I have an M-audio firewire 410. The 410 was not hot plugable and caused the system to crash if it were hot plugged (or unplugged) causing firewire device failure. Then I have to shutdown, disconnect the fw 410, re-boot, reinstall the driver, shut down again, connect the Fw 410 and reboot before it would work again. The iMac's Firewire bus supplies power to its 6 pin connectors at all time, (even when the machine is powered down!). One day the Mac just wouldt power up. My firewire had power but I repeated to push the pwr button and got no result until I unplugged the firewire device. After that it will power up again. Needless to say I have never hot plugged any firewire device in or out of the Mac again. That was back in 2006. Now with or w/o firewire attached I have to tapdance with it to power up by removing the AC cord briefly. I have my AAS degree in Computer Science and I have spent the better part of the last decade at a tech bench troubleshooting and repairing electronics equipment and breathing solder fumes so I know my way around a schematic to say the least. I wipped the Macs Hard drive and performed a clean install of OS 10.4.11. then reinstalled the FW410. It worked great untill I shutdown and went to pwr up again. Same problems occured. Its very inconsistant and doesnt happen every time i shut down. I do notice when I plug in the Ac to the Mac; sometimes i hear a high pitched hum that comes from the power supply and that is when the unit wont respond at all. so I disconnect the AC and reconnect until that noise cant be heard. Then it pwr up ok.
My thought is that the circuits which supply voltage to the F/W bus were poorly designed or faulty or damaged.
My thought is that the circuits which supply voltage to the F/W bus were poorly designed or faulty or damaged.