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    AST RESEARCH, INC.           TECHNICAL BULLETIN # 1205               6-6-95

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    AST DESKTOPS DISPLAYING GARBLED TEXT

    PROBLEM

    AST desktop systems may display garbled text and error message "03:02" at
    boot-up.

    CAUSE

    Noise on the Non-Maskable Interrupt (NMI) lines causes a false NMI to be
    generated.

    SYSTEMS AFFECTED
    AST PART NUMBER AND DESCRIPTION

    501196-XXX          BRAVO 4-25S
    501197-XXX          BRAVO 4-33
    501198-XXX          BRAVO 4-50D
    501199-XXX          BRAVO 4-66D
    501233-XXX          BRAVO 4-33S
    501243-XXX          ADVANTAGE! PLUS 2 486-33
    501244-XXX          ADVANTAGE! PLUS 2 486SX
    501245-XXX          ADVANTAGE! PLUS 2 486SX
    501246-XXX          ADVANTAGE! PLUS 2 486DX2
    501275-XXX          ADVANTAGE! PLUS 2 486SX
    501276-XXX          ADVANTAGE! PLUS 2 486SX
    501290-XXX          BRAVO 4-25S
    501291-XXX          BRAVO 4-33S
    501292-XXX          BRAVO 4-33
    501293-XXX          BRAVO 4-50D
    501300-XXX          BRAVO 4-33S
    501303-XXX          BRAVO 4-33
    501304-XXX          BRAVO 4-25S
    501341-XXX          BRAVO LC 4-33
    501346-XXX          BRAVO 4-33S
    501415-XXX          ADVANTAGE! PLUS 3 486SX
    501416-XXX          ADVANTAGE! PLUS 3 486DX2
    501417-XXX          ADVANTAGE! PLUS 2 486DX2
    501418-XXX          ADVANTAGE! PLUS 3 486SX
    501419-XXX          ADVANTAGE! PLUS 3 486DX
    501445-XXX          ADVANTAGE! PLUS 3 486DX2
    501461-XXX          BRAVO 4-66D
    501560-XXX          BRAVO 4-25S
    510300-XXX          BRAVO 4-33S
    510303-XXX          BRAVO 4-33
    510304-XXX          BRAVO 4-25S

    SOLUTION

    A .33 PF capacitor has been added to the system board between pins 12 and
    13 at location U21.   The solution is to replace the system board.  See part
    numbers and revision below.

    CAUTION

    This modification should be performed ONLY by a qualified service technician.  It is strongly recommended that this change be completed by an
    AST Authorized Service Center.  In no case will AST Research, Inc. be liable
    for damage to the system and its components, or loss of data caused by
    improper modification.

    PREREQUISITES

    A full backup of all data on the hard drive in the computer is strongly
    suggested.

    TIME REQUIRED

    30 minutes.

    STATUS VERIFICATION

    The revision level of the AST Riser card can be identified by observing the
    revision letter at the end of the nine-digit part number located on the solder
    side of the card.

    PARTS REQUIRED
    AST PART NUMBER              DESCRIPTION                REVISION

    202560-000               PCBA MBD ALC2/BLC2            X24 or higher
    202560-001               PCBA MBD A/BLC2 4-25S         X22 or higher
    202560-012               PCBA MBD A/BLC2 4-33          X23 or higher
    202560-013               PCBA MBD A/BLC2 4-33          X24 or higher
    202560-014               PCBA MBD A/BLC2 4-33          X24 or higher
    202560-015               PCBA MBD A/BLC2 4-33          X24 or higher
    202560-017               PCBA MBD A/BLC2 4-50D         X24 or higher
    202560-018               PCBA MBD A/BLC2 4-50D         X25 or higher
    202560-019               PCBA MBD A/BLC2 4-50D         X25 or higher
    202560-021               PCBA MBD A/BLC2 4-66D         X28 or higher
    202560-022               PCBA MBD A/BLC2 4-66D         X29 or higher
    202560-023               PCBA MBD A/BLC2 4-66D         X29 or higher
    202560-024               PCBA MBD A/BLC2 4-66D         X26 or higher
    202560-027               PCBA MBD BLC2 4-33            X17 or higher
    202560-028               PCBA MBD BLC2 4-50D           X19 or higher
    202560-030               PCBA MBD A/BLC2 4-33          X20 or higher
    202560-031               PCBA MBD BLC2 4-66D           X10 or higher
    202560-100               PCBA PIII                     X16 or higher
    202560-101               PCBA MBD A/BLC2 4-25S         X21 or higher
    202560-102               PCBA MBD A/BLC2 4-25S         X21 or higher
    202560-103               PCBA MBD A/BLC2 4-33S         X22 or higher
    202560-104               PCBA MBD A/BLC2 4-33S         X22 or higher
    202560-105               *PCBA MBD A/BLC2 4-33         X09 or higher
    202560-106               *PCBA MBD A/BLC2 4-33         X09 or higher
    202560-107               *PCBA MBD A/BLC2 4-50D        X10 or higher
    202560-108               *PCBA MBD A/BLC2 4-50D        X10 or higher
    202560-109               *PCBA MBD A/BLC2 4-66D        X13 or higher
    202560-110               *PCBA MBD A/BLC2 4-66D        X13 or higher
    202560-111               *PCBA MBD A/BLC2 4-66D        X11 or higher
    202560-112               PCBA MBD B 4-25S              X16 or higher
    202560-113               PCBA MBD B 4-33S              X16 or higher
    202560-600               PCBA MBD ALC2/BLC2            X09 or higher

    TOOLS REQUIRED

    Standard computer tools.

    INSTALLATION PROCEDURE

    Refer to the system Hardware Maintenance Manual.

    Removal and replacement of system "Field Replaceable Units" (FRUs) should only
    be performed according to the installation procedures approved and prescribed
    by AST Research, Inc.

    Remove the Riser card according to procedures approved and prescribed by
    AST Research, Inc.

    CHECK-OUT PROCEDURE

    To verify proper operation of the system upon completion of this change,
    follow the setup and test procedures described in the AST User's Manual.

    NOTE

    Warranty reimbursement for this change requires prior AST Research, Inc.
    approval.

    The warranty on this system will become VOID if this change is completed
    by ANYONE other than an AST Authorized Service Center.