TITLE
    Network Server 500: Why It May Not Power On (5/96)
Article ID:
Created:
Modified: 		19711
5/3/96
5/3/96
TOPIC


    After I added several third-party SCSI devices, my Network Server 500 does not power on. Why?

DISCUSSION


    Overview
    ========
    This document explains the reasons why a Network Server 500 may not power on after the addition of several third-party SCSI devices.

    * NOTE: This discussion does not apply to the Network Server 700.

    Symptom
    =======
    Third-party drive testing at Apple has revealed that some SCSI devices may cause the Network Server 500 power supply to fail to power on. The unit fails to exhibit ANY response (no LED or LCD flash) to a front panel or keyboard power-on request. This problem is only seen if several third-party SCSI devices are installed. Hard drive, tape and CD-ROM Option Kits shipped by Apple do not provoke this problem, nor do many third party drives, tapes, and CD-ROM drives.


    Cause
    =====

    When several third party devices are installed in combination, they exhibit transient (power-on) loads on the +12 volts that exceed the short-circuit detect trip point of the Network Server 500 power supply.

    If you have NOT added third party SCSI devices, it is likely that there is some other cause. The most common of these other causes are:

    1) Rear Keyswitch is not fully locked.
    2) Main Logic Module (Rear Drawer) is not fully seated with all four
    thumbscrews tightened.
    3) Processor Card is not fully seated.


    Workaround
    ==========

    If the "no power on" symptom is experienced, following this procedure allows the power supply to properly power up in the system:

    Step 1
    ------
    Unseat the SCSI devices, but leave the root hard drive plugged in (otherwise you will have to startup from Open Firmware).

    Step 2
    ------
    Unplug the unit from the AC wall outlet for at least 45 seconds.

    Step 3
    ------
    Replug the unit into the AC.

    Step 4
    ------
    Power-on from the keyboard or front panel.

    Step 5
    ------
    Reseat the SCSI devices before AIX starts booting.

    NOTE:
    The power supply is not damaged by the failure to power-on. Unseating the offending SCSI devices will allow the unit to successfully power on.



Document Information
Product Area: Computers
Category: Apple Network Server
Sub Category: Network Server 500 & 700

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