I have an EMC 1864 PowerMac G4 with 1GB RAM, running OS 9.2.1 and 10.4 that I am close to retiring/selling (it is not my primary computer). Sometimes when I press the power or reset button to start up the machine the screen remains black and instead of a grey screen appearing and booting it just shuts down. It typically does this a few times in a row, then it is fine for a large number of boots. Then it happens again during another boot. When it does boots up, it is rock solid. I have tried booting up from a CD and I get a similar rate of boot failures so I do not believe it is a problem with the hard disk. Incidentally I was not able to boot up from the CD by holding the c-key but I was booting into the OS and selecting the CD drive as start up disk and then rebooting but I think this was just a coincidence and evidence of the above problem.
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Intermittent shut down during booting of old PowerMac G4
- Thread starter PliSsK
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Looks like you've got a dual-450MHz Gigabit. There are a few possibilities:
It should go without saying that you need to unplug your Power Mac before you do any of this, but I'm going to say it anyway: unplug your Power Mac!
- Power Supply: although, you said it's booting fine repeatedly and running fine when it does. So I don't think we need to go there just yet.
- Front Panel Board: this is the small board attached to the inside front of your Power Mac that holds the power and reset buttons. If your Power Mac starts up reliably when using a restart command from within the OS, and your only trouble comes from pressing the buttons on the front, this could be the culprit. It's not difficult to replace, and you shouldn't have a problem finding the part for sale online.
- Graphics Card: This will give you issues on startup if it's failing, or if its pins aren't making good physical contact with the AGP slot it sits in. You haven't mentioned any graphical issues, so it's probably not failing. I would pull the card, take some canned air and blow out the AGP slot, then take a cloth soaked in rubbing alcohol (highest % you can get) and use something like a table knife (thin - you don't want to have to force it into the slot; and blunt, you don't want to use a sharp instrument here) to insert it into the AGP slot and run it back and forth to clean it. Give it a minute or two to dry and then blow it out again. While you have the card out, clean the card's contacts with a cloth and alcohol. Once everything is dry, replace the card, making sure to seat it firmly into the slot.
- PRAM battery: Your Power Mac has a ½-AA battery inside near a corner of the logic board. These go bad, it's just a matter of time, and a bad one can cause the issues you describe. Replace that battery, and then make sure you give the CUDA (PMU reset) button a push. The button is on the logic board, right next to the battery.
It should go without saying that you need to unplug your Power Mac before you do any of this, but I'm going to say it anyway: unplug your Power Mac!
Hi Dufus, yes you are right, one of those old dual 450MHz machines. Thank you very much for your input! 
It was very helpful and appreciated.
It was very helpful and appreciated.
Hi Dufus, yes you are right, one of those old dual 450MHz machines. Thank you very much for your input!
Hey, you're welcome! Glad to be of service.
For the sake of others who have a similar problem and may find this thread in the future, could you tell us what happened? Were you able to correct the booting issue?
I have a self-built PC, only a few years old, that is exhibiting the exact same inexplicably intermittent and seemingly random behavior. Quite frustrating.
I also assumed it was possibly the graphics card, but the problem persisted after pulling it. Then I thought maybe a short or bad connection with the front panel power button, but unplugging that wire from the motherboard, and using the button on the M/B itself, didn't solve it.
I'm left with the assumption of a bad power supply. It's an EVGA unit that is on the premium end of their lineup. It has an "Eco" switch that is supposed to save energy in low-power mode, or something, but the failure has presented itself with the switch in both positions.
The only consistency about this issue is that it WILL happen if I power cycle the machine in any way. Whether I put it to sleep or do a full shutdown, I can be sure that it will cut off power at some point after the next wake-up or boot. Often, it tricks me into thinking this time will be different; sometimes it goes an hour or two with no problem. Then, *poof*, power off.
If I leave it on continuously, never using sleep or shutting down, it just runs and runs. I've now had it on for about a week without the cutoff happening. Since I currently can't be without it, I'm just going to avoid any power cycles until I can find a more permanent solution, which is most likely a replacement power supply.
I also assumed it was possibly the graphics card, but the problem persisted after pulling it. Then I thought maybe a short or bad connection with the front panel power button, but unplugging that wire from the motherboard, and using the button on the M/B itself, didn't solve it.
I'm left with the assumption of a bad power supply. It's an EVGA unit that is on the premium end of their lineup. It has an "Eco" switch that is supposed to save energy in low-power mode, or something, but the failure has presented itself with the switch in both positions.
The only consistency about this issue is that it WILL happen if I power cycle the machine in any way. Whether I put it to sleep or do a full shutdown, I can be sure that it will cut off power at some point after the next wake-up or boot. Often, it tricks me into thinking this time will be different; sometimes it goes an hour or two with no problem. Then, *poof*, power off.
If I leave it on continuously, never using sleep or shutting down, it just runs and runs. I've now had it on for about a week without the cutoff happening. Since I currently can't be without it, I'm just going to avoid any power cycles until I can find a more permanent solution, which is most likely a replacement power supply.
Sure sounds like that's the problem. If you're looking to replace your PC's PSU with another "eco" unit, I've had good luck with the Antec Earthwatts series. An EA-380D Green has been powering my Windows 7 Pro system for years without a hitch.
NOTE: Since we're on a PowerPC forum, for the benefit of others I feel it necessary to include a caveat: If you're looking to replace a Power Mac G3/G4's PSU with an ATX unit, don't use one advertising itself as "eco" or "green." This typically means the ATX PSU includes Active PFC (Power Factor Correction) which doesn't play nice with Power Macs' onboard power management systems. In my experience Active PFC causes instability on Power Macs. FWIW.
Thanks for the suggestion. I'm not particularly partial to eco power supplies, and it wasn't among my reasons for originally choosing the EVGA.
I know all brands have glitches, but after this experience, the replacement probably won't be EVGA.
I know all brands have glitches, but after this experience, the replacement probably won't be EVGA.
Not necessarily. My experience has largely been like that - it's either working or it isn't - but others here have related tales of gradual failure. PSU's do contain parts, like capacitors, that can either fail catastrophically or gradually; so it's reasonable that a PSU could just go bad over time. It doesn't have to be an all-or-nothing proposition.
I put in a new PRAM battery, which may have helped, the machine booted up (not hanging on black screen) but it crashed after booting up when running OS X 10.4. The 2nd (empty) hard drive was making funny noises and was not detected, and I disconnected it and rebooted several times and everything appeared to be normal.