Service manual

Service Manual
Check the following:
• the 16 shades displayed
• the mid-coloured border
• the quality of the 'grey scale' display
• the integrity of each test card.
Press F5 if the display is correct, or F8 if not correct, to
continue.
These are subjective tests — note any failures.
If the test fails due to the colours being incorrect or
missing, proceed as follows:
With a full white screen, VIDC IC 54 pins 39,40 and 41
should all have the same signal on them. If not, either
change the main PCB, or see Part 5 - Main PCB fault
diagnosis.
High resolution monochrome display
Before running this test you should ensure that the hi-
resolution monochrome monitor is at least 500mm away
from any other monitor.
The screen of the high resolution monochrome monitor
will display a number of vertical lines, and after you
press either F5 (pass) or F8 (fail) when prompted, a set
of horizontal lines will be added. Check for
• clarity and linearity of lines
• electronic noise affecting the display
• any signs of distortion at the edge of the display. This
is best seen at approximately a metre back from the
screen.
Press the space bar when prompted. This will produce
an inverse video of the display. Make the same checks
again.
Press F5 if correct, or F8 if not, to continue.
This is a subjective test — note any failures.
Action if fails: See Part 5 - Main PCB fault diagnosis.
Standard VGA display
A screen display in mode 27 will appear, consisting of a
series of white lines radiating from the top left hand
corner across which a three-coloured bird will travel from
bottom left to top right, where it will rest. Check
• the accuracy of the lines
• the movement and integrity of the bird/cursor.
Press F5 if correct, or F8 if not correct, to continue.
This is a subjective test — note any failures.
Following this display are four test cards each consisting
of 16 concentric circles beneath a horizontal band. The
band is divided into 16 sections with a pale border
highlighting the leftmost 8 sections (see Note). The
object of the cards is to display 16 shades, the border
should be mid-range.
The four test cards are:
• Red
• Green
• Blue
• Grey scale
Check
• the 16 shades displayed
• the quality of the grey scale display
• the integrity of each test card.
Press F5 if the display is correct, or F8 if not correct, to
continue.
These are subjective tests — note any failures.
Note: The border is removed in the Standard VGA tests,
and the 8 sections of the 16 section bar are only
highlighted below and to the left, NOT above the bar.
Action if fails: See Part 5 - Main PCB fault diagnosis.
Super VGA display
A screen display in mode 31 will appear, consisting of a
series of white lines radiating from the top left hand
corner across which a three-coloured bird will travel from
bottom left to top right, where it will rest. Check
• the accuracy of the lines
• the movement and integrity of the bird/cursor.
Press F5 if correct, or F8 if not correct, to continue.
This is a subjective test — note any failures.
Following this display are four test cards each consisting
of 16 concentric circles beneath a horizontal band. The
band is divided into 16 sections with a pale border
highlighting the leftmost 8 sections (see Note). The object
of the cards is to display 16 shades, the border should be
mid-range. The four test cards are:
• Red
• Green
• Blue
• Grey scale
Check
• the 16 shades displayed
• the quality of the grey scale display
• the integrity of each test card.
Press F5 if the display is correct, or F8 if not correct, to
continue.
These are subjective tests — note any failures.
NOTE: The border is removed in Super VGA tests.
Check how the band is highlighted.
Action if fails: See Part 5 - Main PCB fault diagnosis.
4-10 Issue 2, June 1991 Part 4 - Fault diagnosis