System Will Not POST
[Breadboarding]


H006547 SYSTEM WILL NOT POST (POWER-ON SYSTEM TEST)
       
Note:  This tip is to be used only in unusual situations where routine problem determinations methods have failed. This procedure might be better utilized in a "service shop" type environment.

Symptom:
     POST will not run.  The monitor screen is blank.  There is no audible or visual signals. Multiple FRU replacements, including the system board, have failed to fix this "dead system."

At this point, all HMM (Hardware Maintenance Manual) service procedures and "Undetermined Problem" steps should have already been taken.

The following procedure has proven effective in isolating "dead system" problems that have not been resolved by the established service procedures:

"Bread-board*" the system, using the following procedure:

1. Remove system board, power supply, base memory, diskette drive and cable, etc. from system unit cabinet.

2. Re-assemble the basic ** system outside the cabinet, on a non-conductive surface, using care to prevent individual parts from coming into contact (shorting against each other).

NOTE:

        A. DO NOT place system board on top of an ESD mat or the foam used to pack FRU parts. The ESD mat is CONDUCTIVE.  Some foam (pink & black) used to pack FRUs is treated with a conductive agent to protect parts from ESD (Electro-Static Discharge).

[Ed. Tom: ESD dissipative mats are effectively non-conductive - well, to be more precise they are conductive, but their resistance is somewhere in the megaohm - gigaohm range when measured with a large surface electrodes, so high that you probably won't even be able to measure it with your multimeter and normal probes. So it's perfectly fine to use them as a work surface for your tests and measurements.]

        B. Cardboard, linoleum or a tile floor is acceptable to support system board. (Be aware, the bottom side of a system board may scratch wooden office furniture, and some "black" cardboard may be conductive!)

3. Turn on system power and observe system for signs of POST activity (cursor on monitor, memory count, activity lights flashing, or audible sound).

        A. If system POST runs correctly, inspect interior of cabinet or anything that might be touching the backside of system board.  Look for bent ESD/RFI shields, loose foreign objects, screws, or even tiny slivers of conductive paint near screw heads.

        B. If system still fails to run POST, escalation of problem through hardware support structure is recommended. Yeah. Updated version, ask on comp.sys.ibm.ps2.hardware for help if you haven't done so at the start!

     * "Bread-boarding" refers to assembling an electronic device without a cabinet or other enclosure.  This procedure is routine during development of a product to prove that a given design is functional.

       The advantage of this process is:
       1. It provides visibility to areas that are not easily seen inside the cabinet.
       2. It allows easy access to all the functional system parts.

     ** Note:   It is presumed that all optional adapters have been removed from the system during this process and the system is at a MINIMUM configuration to run POST and provide audible and visual indications of system activity.

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