Mac desktop g4 will not boot up.

Discussion in 'Mac Basics and Help' started by btcomm, Mar 25, 2007.

  1. btcomm macrumors regular

    Joined:
    Oct 18, 2006
    #1
    There seem to be no signs of life. When I push the power button nothing happens at all. I know these macs have a power supply that is difference from PCs as far as physical shape, but it looks like a standard ATX type of connector on the motherboard, can I use another power supply from a PC and connect it up and see if it will turn on?

    Will a desktop G4 turn on while the case is opened?

    If I can use another power supply besides the main ATX connector would there be any other thing I would have to plug in to get the computer to at least power on? I know without HD's hooked up it will not boot all the way, but I just want to see if it will power on.

    Also I know on PCs they have little pins you can short on the motherboard with a screw driver to see if the front power switch is bad, where would these be located on the g4 desktop?
     
  2. Reflow macrumors 68000

    Reflow

    Joined:
    Mar 30, 2005
    Location:
    NJ/PHL
    #3
    When you push the power button does the light come on. If it does does it blink or just turn off. Also does it make any beeps. All this info will help us.
     
  3. btcomm thread starter macrumors regular

    Joined:
    Oct 18, 2006
    #4
    That was helpful thank you dartzorichalcos. I found the ribbon cable and it was snuggly plugged into the logic board and the front of the computer I also unplugged the ribbon cable and tried with a screw driver and nothing powered on so I think the front button is fine.

    I'm still wondering though can a mac g4 desktop turn on while the case is opened? I would think the answer is yes but I don't want to just assume something and have my assumption be wrong.

    Also it looks like a standard ATX power connection, so I was just wondering, for testing purposes can I connect a PC power supply ATX connector to the board and safely test to see if it will power on with another power supply?

    Also, besides the main ATX power connection, is there anything else, like any fans anywhere that would need to be plugged into a working power supply for the computer to boot up? Or would just the main ATX power connector be enough?

    When I push the power button on the front of the case it does not light up at all. The computer makes no beeps at all.
     
  4. spork183 macrumors 6502a

    spork183

    Joined:
    Jul 30, 2006
    #5
    First, it can boot with the case open. Second, you cannot use a PC power supply (well, you can, but it won't work...). Third, try holding the cuda reset button on the motherboard down for a hard count of 10. Then try to boot up.
     
  5. Reflow macrumors 68000

    Reflow

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    Mar 30, 2005
    Location:
    NJ/PHL
    #6
    It seems to me that your pw supply is the problem. I do have a MDD and you can power it up while open. As for replacing it with a pc one. I never tried that and I don't think it will work but I could be wrong
     
  6. btcomm thread starter macrumors regular

    Joined:
    Oct 18, 2006
    #7
    Well, I don't want to believe it but I think the motherboard may be dead. Like I was saying earlier the connector on the motherboard looks identicle to PC's. Looks like a standard ATX connector, I even tried just plugging the power supply into the connector without powering it up to see if it fit and it fit perfectly.

    As far as replacing it with a PC power supply I don't think that is really doable because a PC power supply will not physically fit into the case but I think that testing it might be, it would be nice to get some confirmation, I don't want to order a replacement power supply if that isn't what the problem is. Also is there any website that sells replacement power supply's for a power mac that anyone knows about?
     
  7. Reflow macrumors 68000

    Reflow

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    Mar 30, 2005
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    NJ/PHL
    #8
    The only place that I ever found one is eBay which was in my price range. Good luck
     
  8. dpaanlka macrumors 601

    dpaanlka

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    Nov 16, 2004
    Location:
    Illinois
    #9
    You could replace it with a working G4 power supply.
     
  9. Angrist macrumors 6502

    Joined:
    Mar 11, 2005
    Location:
    MI or NJ
    #10
    If you turn that on it will DESTROY your motherboard. The pinout is different from G4 to PC. You can use a PC PS if you re-wire the main cable ... there are guides around for it, but you can't just swap it.


    Yes, it will boot fine with the case open. Just be careful not to drop anything on the board or short anything. If you leave it on for a long time running box fan over the case is also a good idea, since the case fans won't be where they should be.
     
  10. btcomm thread starter macrumors regular

    Joined:
    Oct 18, 2006
    #11
    Good to know thanks for all your replies.

    Does anyone know how I would even remove the power supply? I took out once screw but it seems like it's pretty solidly in there still. Are the star shaped screws really long and go into the PSU?


    Also one other question, lets say the logic board was dead, would there be any replacements out there?
     
  11. muppetman macrumors newbie

    Joined:
    Mar 30, 2007
    #12
    Hmmmm

    Hi there everybody, new to this forum and I have an issue which is connected to the above....

    I have recently aquired a G4 from work but I didn`t get the monitor that normally comes with it. Problem is, there seems to be an issue with the power button on the front as it doesn`t turn the mac on. The power button on the monitor did, just not this one. This one just doesn`t do anytyhign at all.....

    Could it just be a loose connectionfrom the cable to the motherboard? This is my first Mac since the dawn of AppleMac`s in the early 90`s (VERY early 90`s) and I don`t know how they work.

    Can you get replacement cables if there is an issue with the current one or is it more likely that it is just a loose connection?

    Any help would be very gratefully received.

    Pj.
    :apple:
     
  12. velocityg4 macrumors 68040

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #13
    Well if you want to use an ATX powersupply for testing and possibly replacing I would check this out. This lists the different pin out diagrams of different G4 models.

    http://www.outofspec.com/frankenmac/wire.shtml

    also check this out

    http://www.xlr8yourmac.com/systems/ATX_G4_AGP_conversion/G4_AGP_to_ATX_case_pg2.htm#next

    Since you stated that the ATX plug fit directly into your motherboard I presume you are using a Yikes or Sawtooth G4. This is the easiest mac to get running under a standard ATX powersupply. Be sure of your model is it Yikes, Sawtooth, Gigabit, Digital Audio (DA), Quicksilver or Mirror Drive Door (MDD). Yikes through Digital Audio look similar to one another while Quicksilver and MDD are readily apparent.

    As for replacing your motherboard assuming it is bad just use ebay.

    http://computers.search.ebay.com/g4...ZQQsargnZQ2d1QQsaslcZ2QQsbrftogZ1QQsofocusZbs

    You must be certain of the model G4 you have as you cannot swap boards between different G4 series as they have different powersupply pin-outs and as far as I know stock CPU's unlike aftermarket are not interchangeable.

    If you are unsure of the specific G4 model you have you can look at the motherboards in the ebay ad's to compare yours with the one being sold.
     
  13. velocityg4 macrumors 68040

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #14
    First just check for a loose connection.

    If there is no loose connection you can look for a replacement power button in the apple components section on ebay. These are model specific I think.

    http://computers.search.ebay.com/po...ZQQsargnZQ2d1QQsaslcZ2QQsbrftogZ1QQsofocusZbs
     
  14. muppetman macrumors newbie

    Joined:
    Mar 30, 2007
    #15
    .....

    Thanks for the advice... Will go check out things and see what I can see.

    Thanks again for the help.

    Pj.
    :D
     
  15. liftin macrumors newbie

    Joined:
    Apr 11, 2007
    #16
    dead G4 (MDD)

    I have read all these posts and more. I've been looking for some way to tell for sure if the logic board is dead. To that end I
    - disconnected all peripherals, including keyboard/mouse/monitor
    - removed video card
    - swapped ram modules
    - pressed the reset pram switch
    - removed battery, tested it (OK), waited, then replaced it.
    - removed power supply plug, tested various pins with a voltmeter and got 25V on a a couple pairs of pins, implying that power is OK
    - started up using the button on my cinema display

    When I push the startup button - on either monitor or box - the power LED goes on momentarily (while pushing), and the fans whir to life. I also get the red LED on the motherboard (steady). But NO chime, no display on monitor, no chugging of the startup drive.

    Any options left?

    Thank you so much!!

    Eric
     
  16. joelememac macrumors newbie

    Joined:
    Aug 18, 2008
    #17
    G4 MDD not powering on

    I am having a similar problem with my machine. It was on and running fine. I was opening an audio file that I had opened numerous times before, and it was taking a while so I left that room and when I came back to the room and it was off. I tried restarting and it wouldn't power up. The light flashed momentarily when pressed, and stays on if I hold it, but nothing else powers on; fans, drives, etc. I checked the power supply with a volt meter at pins 1 and 12 and received a 5 volt trickle of power which makes me think it's not the power supply.

    I've reset the pmu, tested the battery disconnected my secondary storage drive. Nothing seems to make a difference.

    Any suggestions???
     
  17. djtrippin macrumors newbie

    Joined:
    Aug 5, 2008
    Location:
    Grand Rapids, MI
    #18
    I had this same problem on a B&W G3 once. I never did figure out the root of the problem. All I know is in the process of trying to trouble shoot it I had at one point unplugged everything from the power supply and then got frustrated and walked away. An hour later when I came back and plugged everything back in and hit the power button on the motherboard, it started right up. I know it sounds silly, but it might be worth a try to unplug everything, wait a while, plug it back in and try again. I never could find the specific problem, and it hasn't happened since.
     
  18. joelememac macrumors newbie

    Joined:
    Aug 18, 2008
    #19
    Thanks for the advice. I took the power supply completely out of the tower for two days and just put it back last night. Still nothing.
     
  19. velocityg4 macrumors 68040

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #20
    If you want to test the powersupply. Unplug it the connect the green power on wire to one of the black negative with a paper clip. This will force the power supply to turn on and the you can test the voltage of every rail. http://www.outofspec.com/frankenmac/wire.shtml Since you mentioned 25V I assume you have a Gigabit or later G4?

    If the powersupply starts up with the paper clip and each rail is the correct voltage then it is fine. If then the Mac will not chime with basically everything removed. Only leave the front panel, front speaker, power, CPU and one RAM module connected. No video card or USB at all, you are testing for the chime. Also swap RAM modules into different slots to rule out a bad slot/module. If you still get no response then I would say with an extremely high probablity that either that CPU or the motherboard is shot.

    Without a spare known good CPU you can not rule that possibility out. So you would most likely have to get both a Mobo and CPU off eBay.
     
  20. joelememac macrumors newbie

    Joined:
    Aug 18, 2008
  21. G4MDD2003 macrumors newbie

    Joined:
    Sep 29, 2008
    #22
    Must be a bad season for the G4 MDD. My dual 1GHz unit just quit. When I press the power button, it lights, fan starts, chime sounds, but nothing on the monitor. Black screen. Verified the monitor/keyboard/mouse with another computer; all good. Tried PRAM reset (P+R+option+cmd+pwr), PMU reset on the logic board, battery replacement, open firmware boot; all with the same result. Removed the RAM, reseated the video card, and powered up. Got a different beep (meaning no RAM?). Put the RAM back in and I’m back to the original symptoms. Probed all 24 pins in the power connector with the connector plugged into the logic board. All voltages seem OK, but I have a question about the green (“power on”) wire. The green wire measures +5v with power off; when I press the power button, the green wire drops to 0v and stays there until I force power off by holding the power button 5+ seconds. Is that the normal behavior for the green wire?

    Any ideas?

    Thanks Much,
    G4MDD2003
     
  22. velocityg4 macrumors 68040

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #23
    Well if it has chimed the motherboard is probably okay.

    Since you have tested everything else I would suspect the video card. If you do not have another one to test with I would suggest a cheapo one off of ebay.
     
  23. christoad macrumors newbie

    Joined:
    Feb 19, 2009
    #24
    Oh dear, my G4 appears to be dead

    I seem to have similar problems to those recorded above. I've just changed the internal CMOS battery on my G4 and now it won't boot. When I hold the power switch on it lights up but there is no other response from the machine. Where do I start????
     
  24. velocityg4 macrumors 68040

    velocityg4

    Joined:
    Dec 19, 2004
    Location:
    Georgia
    #25
    Did you try removing all component except the most basic ones and listen for a start up chime? Also try removing the RAM chips one at a time.
     

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