    AST RESEARCH, INC.         TECHNICAL BULLETIN #0857               08-16-93

                  POWER EXEC 3/25SL COLOR AND CONTRAST DIFFERENCES

    PROBLEM:       Differences in the contrast and brightness controls on the
                   Power Exec 3/25SL Color Notebooks have been observed.

                   When the contrast control on the Power Exec 3/25SL Color
                   Notebook is set at the maximum or the minimum, it is possible
                   that one notebook will have a low contrast image while another
                   has none at all.  One unit may even seem to be have more
                   contrast than others.

    CAUSE:         Due to the technology of Color (STN) LCD Panels, there can be
                   a contrast variation from panel to panel.  This is related to
                   the contrast voltage required to obtain the optimum display.

                   The main objective is that the contrast adjustment is able to
                   produce the optimum contrast in the image within the operating
                   temperature range of the notebook.

                   It is not practical to have all notebooks have the same range
                   of contrast control.  There will also be some differences in
                   the contrast range attributable to the inverters themselves.
                   Inverters are the devices that supply voltage to the panels.
                   The tolerances of the inverters themselves will also vary
                   depending upon the manufacturer.

                   However, there should be a significant amount of contrast
                   adjustment around the optimum point.  The purpose of the
                   adjustment is to compensate for panel tolerances, ambient
                   temperature changes and allow some adjustment of viewing
                   angle.

                   A similar situation with the brightness control also exists.

    AFFECTED
    SYSTEMS:       Power Exec 3/25SL Color (STN) Units

    SOLUTION:      There will be contrast and brightness differences seen between
                   Power Execs caused by a number of factors.  It is not a real
                   problem but just a matter of understanding the limitations of
                   this technology.

                   In some cases there will be a legitimate problem with
                   insufficient brightness due to defective hardware or firmware.
                   These panels should then be replaced through an Authorized
                   Service Center or through AST.