Zenith Z-100 PC series Service Manual page 294

Page
4.8
Troubleshooting
Troubleshooting Table
NOTE: Use of the Disk-Based Diagnostics package, if available, is recom ­
mended for troubleshooting.
Table 4.3 lists some problems that may be encountered and some possible
causes.
Table 4.3. General Troubleshooting Guide
PROBLEM
No video dots.
Horizontal sync problems. Starting characters are off the left
of screen, or first line does not start on the left side of the
screen.
Vertical sync problems. Rolling or starting point off the top
of the screen.
No monochrome (composite) vertical or horizontal sync.
No horizontal or vertical sync.
No horizontal sync.
Mismatched colors with missing intensity.
Background colors incorrect.
No RAM data output.
Cursor not blinking.
Wrong font or white screen.
No dots in graphics mode or wrong dot data.
Random characters and attributes.
POSSIBLE CAUSE
Q301,Q302,Q303,RP306,U345,U346,U342,U324
J305,J306,U341,U324,U325
J302,J303,J304,J313,U340,U341,U349,U324,U325
J302,J303,J305,U341,U346,U349,U324,U325
U341 , U324, U325
J305,U324,U325,U340,U349
RP306,U342,U345,U324,U330,U331,U332,U326,U327,
U334,U333
U324-U327,U33G-U334
U325,U326,U327,U33G-U334
U325
SW301, pin 1, U319, U323-U328, U331-U334
U324-U327,U33G-U334
U319,U323-U328,U33G-U334