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.