Previous 1 2 3 Next 30 Replies Latest reply: Nov 13, 2012 10:13 AM by NoelK99
NoelK99 Level 1 (0 points)

I'm using a MDD G4 Dual 867 Mhz for running older software, and I can't get the unit to start using the power button. Sometimes the button lights up when pressed and sometimes it doesn't but it won't start up unless I have used it that day or the day before and then it will start. Up until now, if I unplug the power cord or open the case and press the PMU button on the logic board, the computer will start using the button. I would like to find out why the unit is doing this so I can possibly repair it, as I want to continue to use it for my older software....Thanks.

Mirror Door G4
  • Texas Mac Man Level 8 (46,565 points)

    Your internal PRAM battery may be weak or discharged. Suggest you replace the battery. Check this site for battery part numbers and sources. Mac PRAM, NVRAM, CUDA/PMU & Battery Tutorial


     Cheers, Tom

  • NoelK99 Level 1 (0 points)

    Thank you. I will try this and report the results.

  • NoelK99 Level 1 (0 points)

    I replaced the battery and still have same problem. Any other suggestions?

  • japamac Level 7 (24,390 points)

    Does the MDD have an ADC port equipped graphics card installed?

    It is possible for an ADC card (due to fault) to interfere with the power functions of the machine.

    Trying a non-ADC port equipped card could test this.


    You may wish to test the PSU to verify that trickle voltage is present when the no start condition occurs:


  • NoelK99 Level 1 (0 points)

    I have a standard apple graphics card. The problem has developed over the last month or 6 weeks, without any additions of new hardware. I will have to get a new multi-meter if I'm going to go through the electrical routine, and if that is not the problem, it might be a power button thing. I'm getting frustrated with this. Maybe I would be better off just getting another MDD G4 that is refurbed, but will cost a lot more to do that. I need Dual Boot, so I'll have to get one that is no faster than 1.25 GHz, am I right?

  • japamac Level 7 (24,390 points)

    The PSU test is a good idea before throwing money at parts (like the power button board).


    Standard graphics cards usually included a card with an ADC port.


    Dual boot capable MDDs were all original models and the 2003 MDD. The FW 800 models were not capable of booting OS 9.

    So, Yes, no faster than 1.25 GHz.


  • NoelK99 Level 1 (0 points)

    Are you saying that some problem could have developed on its own with the video card, although I have not made any changes or additions to it? I don't have another video card laying around to test with. My monitor is an old-style RGB CRT, and I am sharing it with a PCI-X 1.8 GHz G5 hooked up to it with my G4 using a KVM switch.


    If I do the voltage test using a multi-meter and find no faults with it, what should I do next. I would like to save money by just replacing parts if I can, but I would spend the money on an upgraded 1.25 MHz MDD so I can still use my old software. Buying updated software would be much more expensive than replacing the computer, and I still have uses for a few programs thast run on OS9.


    Thanks for info so far.

  • Jacumba Level 4 (2,340 points)

    Video cards do go bad but it's unlikely that it would cause the computer not to start. You would have had prior symptoms of poor video or the computer restarting over and over on it's own.


    There's a good chance the pram battery was bad, that lead to this, which you've replaced. So now that you've replaced the pram battery. Try pressing the cuda button on the motherboard. This should fire up the cooling and power supply fans. If so the computer may boot to the OS? If not the ram may have become corruped.


    So pull all the ram out of the computer and start it, you'll hear one beep. Then shut down the computer. Now insert one ram stick only and start the computer, it should start. Now turn off the computer and repeat this process installing one ram stick at a time and turning off the computer till you have them all back in place.

  • NoelK99 Level 1 (0 points)

    Sorry, I don't know what the "cuda" button is. Could you describe where that is on the motherboard?



  • japamac Level 7 (24,390 points)


  • Jacumba Level 4 (2,340 points)

    I'm not sure where it is on the G4 motherboard? On the G3 I have. There are two small buttons just below the pram battery. The one closest to the battery is the cuda. Perhaps there is a motherboard layout online for your model Mac.

    Also if your not use to working inside the computer case please unplug the power source and be careful of creating static electricity while touching anything in the computer, could damage it. You can do this by wearing a wrist band ground or touching metal before putting your hand inside the case. Carpet flooring can cause static electricity.

  • NoelK99 Level 1 (0 points)

    OK, I know the PMU button...thanks.

  • Jacumba Level 4 (2,340 points)

    Good job lol

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