TITLE
    Power Mac G4 (Gigabit Ethernet): Power Supply Voltage Test
Article ID:
Created:
Modified:
95064
10/19/00
4/23/01

TOPIC

    The Power Mac G4 (Gigabit Ethernet) has no power. To start up, the Power Mac G4 Gigabit Ethernet logic board requires a "trickle" power of +28V. If the system fails to start up, follow the procedure outlined below to determine whether the problem is related to the power supply. This article provides the pinouts for the Power Macintosh G4 (Gigabit Ethernet) power supply connector.


DISCUSSION

    This article covers repair procedures for authorized service providers on selected Apple products, but we have published them in the Knowledge Base for the general public for educational purposes. At this time, there are a limited number of repairs that a customer can perform and these are covered under the customer installable parts program http://www.info.apple.com/installparts . If you have not been authorized to perform these procedures, please contact Apple (800-APL-CARE in the USA) or your local authorized service provider to schedule a repair.

    Symptom

    The computer has no power.

    Products a ffected

    • Power Mac G4 (Gigabit Ethernet)
    Note: If you have a Power Macintosh G3 (Blue and White) or a Power Mac G4 (AGP Graphics/PCI Graphics) with no power, refer to article 58561: " Power Macintosh G3 (Blue and White) and Power Mac G4: Power Supply Voltage Test ".

    Solution

    DANGER! This procedure exposes you to high voltages that can result in death or serious injury. DO NOT ATTEMPT THIS PROCEDURE IF YOU HAVE NOT BEEN CERTIFIED AS AN APPLE-AUTHORIZED TECHNICIAN.

    Refer to the procedure outlined below and Figure 1 to determine whether the problem is related to the power supply.

    Figure 1 Power Supply 22-Pin Connector


      1. Connect the black lead of the volt meter to pin 11 of the 22-pin power supply connector. Connect the red lead of the volt meter to pin 22 of the power supply connector. The volt meter should measure approximately +28V.

      2. If you do not get a reading of +28V, re-check the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply; otherwise, go to the next step.


    3. If you do measure +28V on pin 22, the power supply is likely OK. Go to the next step for further verification.

    4. Start up the computer by pressing the power button on the front of the computer. Note : Verify that the power cable is plugged into
    connector J30. If the computer starts up normally, the power supply is OK. If the computer does not start up, go to the next step.

    5. Check to see if the power supply fan is spinning. If it is not, go to the next step.

    6. Connect the black lead of the volt meter to 11 for Gigabit Ethernet versions. Connect the red lead of the volt meter to pin 1 of the power supply connector.
    The volt meter should measure approximately +3.3V. If you do not get a reading of +3.3V, re-check the volt meter connections and measure the voltage
    again. If voltage is still not present, replace the power supply; otherwise, go to the next step.

    7. Connect the black lead of the volt meter to pin 11 for Gigabit Ethernet versions. Connect the red lead of the volt meter to pin 4 of the power supply
    connector. The volt meter should measure approximately +5V. If you do not get a reading of +5V, re-check the volt meter connections and measure the
    voltage again. If voltage is still not present, replace the power supply; otherwise, go to the next step.

    8. Measure the voltage of pin 10 on the power supply connector. The voltage should measure approximately +12V. If you do not get a reading of +12V,
    re-check the volt meter connections and measure the voltage again. If voltage is still not present, replace the power supply; otherwise, go to the next
    step.

    9. The testing is complete. You have just verified that the power supply is not the cause of the "No power" symptom.


Document Information
Product Area: Power Mac G4
Category: Power Mac G4 Hardware
Sub Category: General Topics; Troubleshooting
Keywords: kpmg4, kssts

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