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sproutsie · Nov 8, 2002, 10:32 AM

hi- i have a friend who just bought a g4 from another friend. yesterday, after he got it, i went over to give him some pointers about how to use a mac, since he is a new convert and is computer-ally challeneged, to boot. he said the thing had suddently shut down once or twice, and the other guy who sold it to him said he needed to get a surge protector. (ohhkay....) but , despite the awesome powers of the new surge protector (snicker) when i was there the g4 kept shutting down randomly, and with increasing frequency.

i tried to run disk warrior, but the computer wouldn't stay alive long enough to get through it, nor through norton, nor through the extended hardware test. the short hardware test was fine. the weird thing is that it doesn't freeze, it just shuts off. no error message when it restarts, or indication that it just shut down. the monitor keeps running, so it isn't his house's power. and when you start it back up again, it is fine (until it shuts off again).

another thing i noticed is that the screen goes dark right before the blue screen loads in os x. i have no experience with g4 desktops- i'm a powerbook person- but honestly, this is ridiculous. i told my friend he needs to have the other guy come over and look at it, and then send it to apple to get fixed- but i am really curious about why this might be happening. the seller said that it had never happened before, so i am wondering if something got jarred in the move, although the buyer told me they were both very careful with it, and it was moved in its original box...

anyway, if anyone has ideas about this, i'd appreciate it- i feel very confused.
thanks!

Rooskibar03 · Nov 8, 2002, 12:32 PM

You didnt tell us what kind of G4 you are working with. Is it a cube?? If so this problem is very common and usually easy to fix.

Need alittle more info..

rampant · Nov 8, 2002, 01:10 PM

It could be an overheating problem, as modern computers have a failsafe shutoff.

reader50 · Nov 8, 2002, 01:33 PM

If the power button sticks in the "in" position, the computer will shut down after 5 seconds. A bad power cord, or one not fully inserted into the G4, can cause this too.

A friend of mine recently Switched to an iMac FP, and didn't push the power cord all the way into the iMac. Whenever the iMac or the cords at the back were nudged, it would shut down. Fortunately, I found this before the Mac newness wore off, and he's still a happy Switcher.

sproutsie · Nov 8, 2002, 02:08 PM

sorry for lack of info- it's one of the g4 towers, bought within the last year. i don't know what else i can tell you- i know it has 512 mgs ram, but other than that, i am not sure.

we checked the power cord, so i don't think it is that. besides, there was nothing to nudge it- it would shut down without any change in its environment- just poof- power off. the power button didn't seem to be stuck- i thought of that, but it was fine. alos, we could restart and have it up for several minutes or for half a minute- it didn't seem like an automatic response ot naything we were doing or to something the computer was doing. as for overheating- the fan wasn't noticeably over-worked- and i felt the case, which wasn't hot, the computer is in a well-ventilated location, and so...dunno!

McDriver · Nov 9, 2002, 02:30 PM

Originally posted by sproutsie:
sorry for lack of info- it's one of the g4 towers, bought within the last year. i don't know what else i can tell you- i know it has 512 mgs ram, but other than that, i am not sure.

we checked the power cord, so i don't think it is that. besides, there was nothing to nudge it- it would shut down without any change in its environment- just poof- power off. the power button didn't seem to be stuck- i thought of that, but it was fine. alos, we could restart and have it up for several minutes or for half a minute- it didn't seem like an automatic response ot naything we were doing or to something the computer was doing. as for overheating- the fan wasn't noticeably over-worked- and i felt the case, which wasn't hot, the computer is in a well-ventilated location, and so...dunno!

A friend of mine had some problems whith his G4 after a couple of blackouts and his powermodule (or what is it called the box where the electricity comes in to your computer) had to be exchanged.

asagoo · Nov 9, 2002, 03:08 PM

This happens with my own PowerMac Dual 867 (mirrored drive doors).
However, the problem is not the computer, but the display. The power button on the Studio Display sometimes just activates itself. If it stays activated for more than five seconds, this shuts down the machine. It also sometimes starts up in the middle of the night.
If he has one of those displays, check whether the power button is lit when the machine shuts down. If so, read this technote:
Apple Studio Display LCD (ADC): Random Sleep, Shut Down, Opening of Monitors Control Panel

Amar

Mac Zealot · Nov 9, 2002, 03:58 PM

Sounds like a bad power supply to me... as that would explain the sudden power-off

snerdini · Nov 9, 2002, 06:39 PM

Can you turn the computer back on immediately after it shuts itself off? We had a bad power supply on one of our Suns at work and I would have to wait about 10-20 minutes before I could turn the computer back on again...the power supply was overheating and needed to cool down.

mrchin · Nov 10, 2002, 01:13 PM

First, you should check the power cord. Possibly borrow another to see if it solves it. Next is checking if the fan is funcitoning and also checking the fan power cabel to make sure its secure. Then, the next step is to verify that the heat sink is properly seated on the processor. I wouldn't recommend trying to adjust it yourself as it is better left to an authorized service provider.

If a hardware repair is needed, the parts to replace would be Power Supply or the Logic Board in that order.

Todd Madson · Nov 10, 2002, 01:58 PM

The power supply has a fail safe mode.

If the power supply senses that there is no more current draw on the
power connector for the fan (i.e. resistance) it shuts the power supply
down to save the machine.

The fan in the power supply probably needs replacing, it's a fairly easy
job if you are electronically capable.

Mine needed replacing after two years of 24x7 operation, fairly common
since the fans in those supplies are junk.

iamnid · Nov 14, 2002, 03:13 PM

a few years back I had a refurbished slot-load iMac that would do the same thing. It wasn't consistent so I had lots of trouble trying to figure out what was wrong.

Eventually I got fed up with it and I took it in to an apple reseller to look at it about a day before the 90day warranty expired. The powerbutton was defective or something (I had noticed that it was not springy like it should have been) -- anyway, never had that problem again.

Cipher13 · Nov 15, 2002, 06:24 AM

The first thing to check... is it a consistent (roughly) amount of time between power-on and power-off each time?

Deal · Nov 15, 2002, 05:45 PM

Lots of good advice here so far. In addition, make sure ALL the cables inside the case are nicely tucked in. Make sure none are "stuck" anywhere (especially around where the door closes and where the bracket that holds the hard drive or optical drive. When someone slides these in they can squish a cable). Make sure the insulation on all the cables is intact.

Next make sure that nothing got stuck under the motherboard that might be shorting it out (old screw, paperclip, dime...).

Disconnect all peripherals ( including keyboard ) and try messing around with it using the mouse.

Reset the powermanager on the motherboard (small button near battery). Next pull the battery out for a while. Then put it back and try again.

Good luck.