Problem when booting my G4 Mirror Door 1.25GHz

My G4 was in every day use until recently when one morning it refused to boot. Basically the symptoms are you push the power button & the light on the power button comes on but nothing else & when you let the button go the light goes off. It was working fine the day befor & I have tried resetting the PMU but made no difference.

Any ideas?

Cheers

Try one of these from Apple's Knowledge Base articles, see where this takes you.

1 - Troubleshooting: My computer won't turn on

2 - Power Mac G4: Screen is Black, No Startup Tone, Drive Does Not Operate (a How To for resetting the CUDA chip in that article)

3 - You could also try unplugging it from the electrical outlet and letting it sit for 10 minutes : this will help drain the capacitors. Plug it back in and see if it responds.

Report back and let us know how these went for you. Good luck !

MDD can sometimes respond the way described if PRAM battery runs dead flat. Try replacing, reset PMU and see if there is any joy?

MDD Startup Issue...

I figured I'd just bump this post since the original poster's issue is similar with my current experience. I have a 1.25 MDD G4 that will not start up. The power button when pressed lights, but fades out when released. The tower was recently unplugged for about a week and hasn't worked since, but before that time it's ran flawlessly since purchased in '04. I've tried resetting the PMU in a multitude of ways. I've replaced the battery not with a newly purchased one, but one from a working mac and still no luck. Also tried starting up w/out the battery, but didn't work. Unplugging and plugging it does nothing either. So, i'm wondering if there are any suggestions short of replacing the PMU?

BTW, i'm assuming that it's not a battery issue since it won't startup when changed or with the battery out of it. I have a quicksilver unit which starts up with or w/out the battery, so I assume the MDD should be no different. So frustrating! Any ideas would be appreciated

Have you tried resetting the PMU or CUDA switch ~ see link 2 in MacHeadCase post. If all that has failed sounds like it is the power supply unit which do fail in MDD.

You might like to do a Google for a second hand unit and instructions on installation.

This one of the most common G4 problems

Okay after extensive searching and undetermined problems of what could be the wrong with my with my G4. Steps I would try: remove any and all usb cables. Firewire cables especially, because firewire connections are known to create faults. Keyboards, mice. Open case door before power up with tower unplugged, press power button briefly and it should light up for a second then shut off. Next remove ram cards and replace only one, this will help upon pre determining possible problems. Next make sure every thing is seated correctly ram, pmu battery, Ide/sata cables, power cables, anything that looks to be plugged into something. Next with door open, plug in power cable and power on. Notice a red light illuminates on the logic board, if so you have power to the board, if no light possible power supply issue exists.
Now if your tower starts up as usual try one step elimination by connecting each additional rams, again with tower unplugged, and additional usb and firewire cables you may find that one of these items gone bad can wreak havoc for you.
Hard drive process of elimination can prove responsive to this type of problem as well, blue screen? Flashing folder image? no drives found cant read drive? Post questions or PM, let me know how you do!!!!!

powermac G5 said:

Okay after extensive searching and undetermined problems of what could be the wrong with my with my G4. Steps I would try: remove any and all usb cables. Firewire cables especially, because firewire connections are known to create faults. Keyboards, mice. Open case door before power up with tower unplugged, press power button briefly and it should light up for a second then shut off. Next remove ram cards and replace only one, this will help upon pre determining possible problems. Next make sure every thing is seated correctly ram, pmu battery, Ide/sata cables, power cables, anything that looks to be plugged into something. Next with door open, plug in power cable and power on. Notice a red light illuminates on the logic board, if so you have power to the board, if no light possible power supply issue exists.
Now if your tower starts up as usual try one step elimination by connecting each additional rams, again with tower unplugged, and additional usb and firewire cables you may find that one of these items gone bad can wreak havoc for you.
Hard drive process of elimination can prove responsive to this type of problem as well, blue screen? Flashing folder image? no drives found cant read drive? Post questions or PM, let me know how you do!!!!!

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I've unplugged everything, reseated the ram and video card. I have'nt tried unplugging the internal hard drives (x3); maybe ill try that next. Again, I have not tried replacing the battery with a freshly purchased one ($20), but i'm pretty sure it would startup without one as my quicksilver does so just fine. Can anyone confirm my assumption? I also read somewhere that there is a fuse within the PMU that can blow, but if this were the case the power light wouldn't illuminate at all right?

Some additional info. I recently moved and while doing so, my computer was unplugged for about a week. It worked fine the day I actually moved my computer as I was using it right before I packed it up.A week later on the morning I tried firing it up the tower had sat in a room overnight that was quite cold. Could the cold temps have screwed things up?

This is bummer; moving has stressed me out enough and now I find that my computer, which has never been abused and is in near mint cond., hadn't survived the trip? It was only 20mi....Bogus!

Okay not to sure about the fuse but if you have a volt meter or know someone who does you can test the voltage of the battery, not likely to be your problem. Now that I know that you have 3 hard drives I would definitely disconnect all but you primary boot drive and see if that will help, just out of curiosity try to hold the alt/ option key on your keyboard at start up to see if it will bring up your drive option screen. If you have any drives plugged in it should allow you to choose a start up drive if any or all are connected it should show them. Do you have a fire wire cable? If so we can try to boot your malfunctioning mac off your good one or vice versa and try to correct any problems from there.

powermac G5 said:

Okay not to sure about the fuse but if you have a volt meter or know someone who does you can test the voltage of the battery, not likely to be your problem. Now that I know that you have 3 hard drives I would definitely disconnect all but you primary boot drive and see if that will help, just out of curiosity try to hold the alt/ option key on your keyboard at start up to see if it will bring up your drive option screen. If you have any drives plugged in it should allow you to choose a start up drive if any or all are connected it should show them. Do you have a fire wire cable? If so we can try to boot your malfunctioning mac off your good one or vice versa and try to correct any problems from there.

Click to expand...

The problem is that I can't even get a screen. The power button while depressed illuminates then goes out upon release and that's about it; no fans, drive activity etc... My research online has led me to believe that the PMU will need replacing. However, i'm willing to try with a newly purchased battery before handing out $180 for unit, it is cost effective. I have read around that some model macs will exhibit similar symptoms with a bad or w/out a battery. I wish someone from here could confirm whether or not the 1.25ghz MDD works w/out the battery installed....anyone???

Okay, this seems frustrating. Your PMU battery is solely for remembering the time and date and settings, so no I don't think that the battery will be necessary for start up. Did you try the reset button on the board next to the battery. And have you looked for schematics on your machine possibly to locate the fuse? Test your battery before buying a new one if you do not have a volt meter go to radio shack they carry the half double A, but ask them to test your battery for you first, they will have a volt meter. 20 is alot for a little battery, I have had to buy one for my G4. I have also been running a G5 flawlessly for some time now, think about a possible upgrade. As well let me know your outcome as I am here with you on this.

I have a similar problem and one shared by other MDD owners. Hold power button, flashes slowly then goes out. Fans whirr up like a 747 and then nothing. Only shuts down by holding power button in. Have tried replacing RAM chips, reset PMU, bought new logic board and CPU/Heatsink. The only thing i haven't tried is replacing Power supply, but with fans on and red light on logic board i can't see it being a power issue. Have also tried working through Apple's diagnostics and the last item on the list is replace power supply. Could it really be the power supply when i seem to have power to the board?. One interesting aside is that when i replaced logic board and cpu the machine got half way through boot up and then froze. After that one time it displayed same symptoms as above.