ThePup66
Level 1 (4 points)
Desktops

Q: G4 DP500 Power Problems

Wouldn't power up a couple of months ago. Randomly one day after several weeks I hit the power button and it was fine. Have used it 4-5 times over a couple of weeks since then. Tonight after about 3-4 minutes it shut down as if the power cord had been pulled. It will not power up. I was using a browser when it happened. I know the AC cord is live, I can hear the small electrical click when the contacts make a connection with the machine. The PRAM(?) battery reads 3.7v with a meter. I removed it for 10 minutes for a reset to no avail. I do not see any lit LEDs on the motherboard although I don't recall ever seeing one but I have read that maybe there is one. (A few years ago I replaced the power supply after the tower would not power up following a neighborhood power outage due to lightning. We seem to have several outages each year in this area. Just background info, don't know if there's any relation to current problem. )

PowerMac

Posted on Aug 2, 2016 12:29 AM

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ThePup66

Q: G4 DP500 Power Problems

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  • by BDAqua,

    BDAqua BDAqua Aug 2, 2016 1:57 AM in response to ThePup66
    Level 10 (123,467 points)
    Aug 2, 2016 1:57 AM in response to ThePup66

    Hello,

     

    Was the battery check done with a 1K resistor in series?

     

    Was the power cord & all peripherals disconnected when you removed the battery for 10 min.?

  • by ThePup66,

    ThePup66 ThePup66 Aug 2, 2016 10:40 AM in response to BDAqua
    Level 1 (4 points)
    Desktops
    Aug 2, 2016 10:40 AM in response to BDAqua

    Thanks for the quick reply. Sorry, don't understand 1st question - my tech knowledge is limited. I took the battery out and checked it with my Ideal model 61-746 meter set to measure DC voltage.  Only disconnected power cord (then pushed startup button) before pulling the battery for 10 minutes. Saw the procedure steps listed in another thread. There was no mention of disconnecting everything.

  • by BDAqua,

    BDAqua BDAqua Aug 2, 2016 11:28 AM in response to ThePup66
    Level 10 (123,467 points)
    Aug 2, 2016 11:28 AM in response to ThePup66

    Well, long shot, but I'd try disconnecting everything, PRAM B attery, AC, Monitor, Printer, everything, let sit 1 hour, hold start button 2 seconds, replace everything & try again.

     

    Sometimes reseating RAM & Graphic cards, and/or Logic board connectors helps.

     

    I'll try to keep watch if you have anything more to report.

  • by ThePup66,

    ThePup66 ThePup66 Aug 4, 2016 1:24 AM in response to BDAqua
    Level 1 (4 points)
    Desktops
    Aug 4, 2016 1:24 AM in response to BDAqua

    No change.  Should there be a lit LED on the motherboard?

  • by BDAqua,

    BDAqua BDAqua Aug 4, 2016 8:29 AM in response to ThePup66
    Level 10 (123,467 points)
    Aug 4, 2016 8:29 AM in response to ThePup66

    Sorry, bitten by the Jive SW bug that won't let me see the last post if logged in. L(

     

    I believe there is supposed to be a red LED lit if you have 5 VDC for start up on the logic board, but have trouble finding proof.

     

    Maybe this could help...

     

    https://www.ifixit.com/Device/Power_Mac_G4_M5183

  • by Castor Bricoleur,Helpful

    Castor Bricoleur Castor Bricoleur Aug 23, 2016 10:28 PM in response to ThePup66
    Level 1 (9 points)
    Aug 23, 2016 10:28 PM in response to ThePup66

    You need to check the power supply as your computer should turn on even with a dead battery. The tricky part about these old Macs is that unlike a standard ATX PC they have a 28V stand by voltage instead of 5V. This 28V also powers the FireWire ports and the ADC monitor. Here's how to check it :

    -Unplug all logic board and drive power connectors

    -Plug in your AC cord

    -With a voltmeter on DC Volts setting, check voltage on logic board connector between pin 22 (white wire) and any GND (black) wire. You should have 28V. If not, power supply is faulty.

    -If you do have 28V, short pin 15 (green wire) to ground (black wire) with a jumper. This should turn on the power supply, if not it is faulty

    -With the power supply on, test all voltage on connector, see this link for details : http://atxg4.com/gige-da.html. If everything is ok, search elsewhere, if not you will have to replace your power supply.

     

    The site mentioned above will give you a way of using an ATX power supply in your Mac, but with limitations. I have a solution is a bit more expensive but uses an external 28V power supply, so the FireWire ports and deep sleep will work fine. If you choose a big enough power supply you could also use an ADC monitor. I don't know what are your requirements on this... Let me know if you are interested.

  • by ThePup66,

    ThePup66 ThePup66 Aug 23, 2016 10:35 PM in response to Castor Bricoleur
    Level 1 (4 points)
    Desktops
    Aug 23, 2016 10:35 PM in response to Castor Bricoleur

    I'm getting 0.0 and an occasional 0.1.  You seem more knowledgeable than others who have replied on another forum.  Another person suggested replacing the battery but I don't see how the meter test from pin 22 would even involve the battery. I guess I'll be shopping for another power supply.  Should there be an LED indicating power somewhere on the board of this model?

  • by Castor Bricoleur,

    Castor Bricoleur Castor Bricoleur Aug 27, 2016 8:58 AM in response to ThePup66
    Level 1 (9 points)
    Aug 27, 2016 8:58 AM in response to ThePup66

    If you don't have 28V on pin 22, replacing the battery won't change anything. You will have to replace the power supply.

     

    There is a red LED near the ram slots but only lights up when the computer is on.

     

    Good luck!